[Show abstract][Hide abstract] ABSTRACT: Four B-class MADS box genes specify petal and stamen organ identities in tomato. Several homeotic mutants affected in petal and stamen development were described in this model species, although the causal mutations have not been identified for most of them. In this study we characterized a strong stamenless mutant in the tomato Primabel cultivar (sl-Pr), which exhibited homeotic conversion of petals into sepals and stamens into carpels and we compared it with the stamenless mutant in the LA0269 accession (sl-LA0269). Genetic complementation analysis proved that both sl mutants were allelic. Sequencing revealed point mutations in the coding sequence of the Tomato APETALA3 (TAP3) gene of the sl-Pr genome, which lead to a truncated protein, whereas a chromosomal rearrangement in the TAP3 promoter was detected in the sl-LA0269 allele. Moreover, the floral phenotype of TAP3 antisense plants exhibited identical homeotic changes to sl mutants. These results demonstrate that SL is the tomato AP3 orthologue and that the mutant phenotype correlated to the SL silencing level. Expression analyses showed that the sl-Pr mutation does not affect the expression of other tomato B-class genes, although SL may repress the A-class gene MACROCALYX. A partial reversion of the sl phenotype by gibberellins, gene expression analysis, and hormone quantification in sl flowers revealed a role of phytohormones in flower development downstream of the SL gene. Together, our results indicated that petal and stamen identity in tomato depends on gene-hormone interactions, as mediated by the SL gene.
Journal of Experimental Botany 03/2014; · 5.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The QTLs analyses here reported demonstrate the significant role of both individual additive and epistatic effects in the genetic control of seed quality traits in the Andean common bean. Common bean shows considerable variability in seed size and coat color, which are important agronomic traits determining farmer and consumer acceptability. Therefore, strategies must be devised to improve the genetic base of cultivated germplasm with new alleles that would contribute positively to breeding programs. For that purpose, a population of 185 recombinant inbred lines derived from an Andean intra-gene pool cross, involving an adapted common bean (PMB0225 parent) and an exotic nuña bean (PHA1037 parent), was evaluated under six different-short and long-day-environmental conditions for seed dimension, weight, color, and brightness traits, as well as the number of seed per pod. A multi-environment Quantitative Trait Loci (QTL) analysis was carried out and 59 QTLs were mapped on all linkage groups, 18 of which had only individual additive effects, while 27 showed only epistatic effects and 14 had both individual additive and epistatic effects. Multivariate models that included significant QTL explained from 8 to 68 % and 2 to 15 % of the additive and epistatic effects, respectively. Most of these QTLs were consistent over environment, though interactions between QTLs and environments were also detected. Despite this, QTLs with differential effect on long-day and short-day environments were not found. QTLs identified were positioned in cluster, suggesting that either pleiotropic QTLs control several traits or tightly linked QTLs for different traits map together in the same genomic regions. Overall, our results show that digenic epistatic interactions clearly play an important role in the genetic control of seed quality traits in the Andean common bean.
Theoretical and Applied Genetics 01/2014; · 3.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Common bean is an important vegetable legume in many regions of the world. Size and color of fresh pods are the key factors for deciding the commercial acceptance of bean as a fresh vegetable. The genetic basis of important horticultural traits of common bean is still poorly understood, which hinders DNA marker-assisted breeding in this crop. Here we report the identification of single-locus and epistatic quantitative trait loci (QTLs), as well as their environment interaction effects for six pod traits, namely width, thickness, length, size index, beak length and color, using an Andean intra-gene pool recombinant inbred line population from a cross between a cultivated common bean and an exotic nuña bean. The QTL analyses performed detected a total of 23 QTLs (single-locus QTLs and epistatic QTLs): five with only individual additive effects and six with only epistatic effects, while the remaining twelve showed both effects. These QTLs were distributed across linkage groups (LGs) 1, 2, 4, 6, 7, 8, 9, 10 and 11; particularly noteworthy are the QTLs for pod size co-located on LGs 1 and 4, indicative of tight linkage or genes with pleiotropic effects governing these traits. Overall, the results obtained showed that additive and epistatic effects are the major genetic basis of pod size and color traits. The mapping of QTLs including epistatic loci for the six pod traits evaluated provides support for implementing marker-assisted selection toward genetic improvement of common bean.
[Show abstract][Hide abstract] ABSTRACT: Nuña beans (Phaseolus vulgaris L.), an ancient and pre-ceramic landrace native to Andean region, possess the property of popping and a high content of proteins and carbohydrates, which makes it an alternative nutritious snack. Knowledge on the genetic bases of popping ability is relevant for common bean improvement. Progenies derived from two nuña bean crosses were used in a generation mean based mating design to determine the inheritance and gene action for five popping related traits: length of popped seeds (PSL), popping dimension index (PDI), percentage of un-popped seeds (PUS), popping percentage average (PPA) and expansion coefficient (EC). Significant additive gene effects were found for all traits, and was the only source of the observed variation for PSL, while dominance and higher-order interactions among loci contributed to the genetic divergence for the other traits. The dominance of the cultivated over nuña alleles for PDI, PPA, EC and PUS, was confirmed by high mid-parent heterosis values and generation mean comparisons. The [d] and [dd] gene effects were in opposite direction for PPA and EC, indicating duplicate epistasis. Therefore, epistasis is likely to be an important explanation for the heterosis in both traits. For PDI and PUS, the opposite signs for [aa] and [dd] gene effects indicated that the genes for increasing popping are dispersed between the parents. Generation means and variances of BC1P2 indicated advantages of the backcross breeding procedure to improve the adaptation of the exotic germplasm and at the same time, transfer part of the desired donor genes to cultivated common bean. The backcross to the nuña parent could be an alternative to maintain/recover the favorable epistatic gene combinations found for PDI, PPA, EC and PUS traits.
[Show abstract][Hide abstract] ABSTRACT: Chlorpyrifos (CPF) is an organophosphate (OP) insecticide that is metabolically activated to the highly toxic chlorpyrifos oxon. Dietary exposure is the main route of intoxication for non-occupational exposures. However, only limited behavioral effects of chronic dietary exposure have been investigated. Therefore, male Wistar rats were fed a dose of 5mg/kg/day of CPF for thirty-one weeks. Animals were evaluated in spatial learning and impulsivity tasks after 21 weeks of CPF dietary exposure and one week after exposure ended, respectively. In addition, the degree of inhibition of brain acetylcholinesterase (AChE) was evaluated for both the soluble and particulate forms of the enzyme, as well as AChE gene expression. Also, brain acylpeptide hydrolase (APH) was investigated as an alternative target for OP-mediated effects. All variables were evaluated at various time points in response to CPF diet and after exposure ended. Results from behavioral procedures suggest cognitive and emotional disorders. Moreover, low levels of activity representing membrane-bound oligomeric forms (tetramers) were also observed. In addition, increased brain AChE-R mRNA levels were detected after four weeks of CPF dietary exposure. However, no changes in levels of brain APH were observed among groups. In conclusion, our data point to a relationship between cognitive impairments and changes in AChE forms, specifically to a high inhibition of the particulate form and a modification of alternative splicing of mRNA during CPF dietary exposure.
[Show abstract][Hide abstract] ABSTRACT: Organophosphates (OPs) affect behavior by inhibiting acetylcholinesterase (AChE). While the cognitive short-term effects may be directly attributed to this inhibition, the mechanisms that underlie OP's long-term cognitive effects remain controversial and poorly understood. Accordingly, two experiments were designed to assess the effects of OPs on cognition, and to ascertain whether both the short- and long-term effects of are AChE-dependent. A single subcutaneous dose of 250 mg/kg chlorpyrifos (CPF), 1.5 mg/kg diisopropylphosphorofluoridate (DFP) or 15 mg/kg parathion (PTN) was administered to male Wistar rats. Spatial learning was evaluated 72 h or 23 weeks after exposure, and impulsive choice was tested at 10 and 30 weeks following OPs administration (experiment 1 and 2, respectively). Brain soluble and membrane-bound AChE activity, synaptic AChE-S mRNA, read-through AChE-R mRNA and brain acylpeptide hydrolase (APH) activity (as alternative non-cholinergic target) were analyzed upon completion of the behavioral testing (17 and 37 weeks after OPs exposure). Both short- and long-term CPF treatment caused statistically significant effects on spatial learning, while PTN treatment led only to statistically significant short-term effects. Neither CPF, DFP nor PTN affected the long-term impulsivity response. Long-term exposure to CPF and DFP significantly decreased AChE-S and AChE-R mRNA, while in the PTN treated group only AChE-S mRNA levels were decreased. However, after long-term OP exposure, soluble and membrane-bound AChE activity was indistinguishable from controls. Finally, no changes were noted in brain APH activity in response to OP treatment. Taken together, this study demonstrates long-term effects of OPs on AChE-S and AChE-R mRNA in the absence of changes in AChE soluble and membrane-bound activity. Thus, changes in AChE mRNA expression imply non-catalytic properties of the AChE enzyme.
[Show abstract][Hide abstract] ABSTRACT: Exposure to organophosphates (OPs) can lead to cognitive deficits and oxidative damage. Little is known about the relationship between behavioral deficits and oxidative stress within the context of such exposures. Accordingly, the first experiment was carried out to address this issue. Male Wistar rats were administered 250 mg/kg of Chlorpyrifos (CPF), 1.5 mg/kg of Diisopropylphosphorofluoridate (DFP) or 15 mg/kg of Parathion (PTN). Spatial learning in the water maze task was evaluated, and F2-isoprostanes (F2-IsoPs) and prostaglandin (PGE2) were analyzed in the hippocampus. A second experiment was designed to determine the degree of inhibition of brain acetylcholinesterase (AChE) activity, both the soluble and particulate forms of the enzyme, and to assess changes in AChE gene expression given evidence on alternative splicing of the gene in response to OP exposures. In addition, brain acylpeptide hydrolase (APH) activity was evaluated as a second target for OP-mediated effects. In both experiments, rats were sacrificed at various points to determine the time-course of OPs toxicity in relation to their mechanism of action. Results from the first experiment suggest cognitive and emotional deficits after OPs exposure, which could be due to, at least in part, increased F2-IsoPs levels. Results from the second experiment revealed inhibition of brain AChE and APH activity at various time points post OP exposure. In addition, we observed increased brain AChE-R mRNA levels after 48h PTN exposure. In conclusion, the present study provides novel data on the relationship between cognitive alterations and oxidative stress, and the diverse mechanisms of action along a temporal axis in response to OP exposures in the rat.
[Show abstract][Hide abstract] ABSTRACT: A novel source of resistance to two-spotted spider mite (Tetranychus urticae Koch) was found in Solanum pimpinellifolium L. accession TO-937 and thereby a potential source of desirable traits that could be introduced into new tomato varieties. This resistance was found to be controlled by a major locus modulated by minor loci of unknown location in the genome of this wild tomato. We first applied a bulked segregant analysis (BSA) approach in an F(4) population as a method for rapidly identifying a genomic region of 17 cM on chromosome 2, flanked by two simple sequence repeat markers, harboring Rtu2.1, one of the major QTL involved in the spider mite resistance. A population of 169 recombinant inbred lines was also evaluated for spider mite infestation and a highly saturated genetic map was developed from this population. QTL mapping corroborated that chromosome 2 harbored the Rtu2.1 QTL in the same region that our previous BSA findings pointed out, but an even more robust QTL was found in the telomeric region of this chromosome. This QTL, we termed Rtu2.2, had a LOD score of 15.43 and accounted for more than 30 % of the variance of two-spotted spider mite resistance. Several candidate genes involved in trichome formation, synthesis of trichomes exudates and plant defense signaling have been sequenced. However, either the lack of polymorphisms between the parental lines or their map position, away from the QTL, led to their rejection as candidate genes responsible for the two-spotted spider mite resistance. The Rtu2 QTL not only serve as a valuable target for marker-assisted selection of new spider mite-resistant tomato varieties, but also as a starting point for a better understanding of the molecular genetic functions underlying the resistance to this pest.
Theoretical and Applied Genetics 08/2012; · 3.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Nuna bean is a type of ancient common bean (Phaseolus vulgaris L.) native to the Andean region of South America, whose seeds possess the unusual property of popping. The nutritional features of popped seeds make them a healthy low fat and high protein snack. However, flowering of nuna bean only takes place under short-day photoperiod conditions, which means a difficulty to extend production to areas where such conditions do not prevail. Therefore, breeding programs of adaptation traits will facilitate the diversification of the bean crops and the development of new varieties with enhanced healthy properties. Although the popping trait has been profusely studied in maize (popcorn), little is known about the biology and genetic basis of the popping ability in common bean. To obtain insights into the genetics of popping ability related traits of nuna bean, a comprehensive quantitative trait loci (QTL) analysis was performed to detect single-locus and epistatic QTLs responsible for the phenotypic variance observed in these traits. RESULTS: A mapping population of 185 recombinant inbred lines (RILs) derived from a cross between two Andean common bean genotypes was evaluated for three popping related traits, popping dimension index (PDI), expansion coefficient (EC), and percentage of unpopped seeds (PUS), in five different environmental conditions. The genetic map constructed included 193 loci across 12 linkage groups (LGs), covering a genetic distance of 822.1 cM, with an average of 4.3 cM per marker. Individual and multi-environment QTL analyses detected a total of nineteen single-locus QTLs, highlighting among them the co-localized QTLs for the three popping ability traits placed on LGs 3, 5, 6, and 7, which together explained 24.9, 14.5, and 25.3 % of the phenotypic variance for PDI, EC, and PUS, respectively. Interestingly, epistatic interactions among QTLs have been detected, which could have a key role in the genetic control of popping. CONCLUSIONS: The QTLs here reported constitute useful tools for marker assisted selection breeding programs aimed at improving nuna bean cultivars, as well as for extending our knowledge of the genetic determinants and genotype x environment interaction involved in the popping ability traits of this bean crop.
[Show abstract][Hide abstract] ABSTRACT: Salinity and drought have a huge impact on agriculture since there are few areas free of these abiotic stresses and the problem continues to increase. In tomato, the most important horticultural crop worldwide, there are accessions of wild-related species with a high degree of tolerance to salinity and drought. Thus, the finding of insertional mutants with other tolerance levels could lead to the identification and tagging of key genes responsible for abiotic stress tolerance. To this end, we are performing an insertional mutagenesis programme with an enhancer trap in the tomato wild-related species Solanum pennellii. First, we developed an efficient transformation method which has allowed us to generate more than 2,000 T-DNA lines. Next, the collection of S. pennelli T(0) lines has been screened in saline or drought conditions and several presumptive mutants have been selected for their salt and drought sensitivity. Moreover, T-DNA lines with expression of the reporter uidA gene in specific organs, such as vascular bundles, trichomes and stomata, which may play key roles in processes related to abiotic stress tolerance, have been identified. Finally, the growth of T-DNA lines in control conditions allowed us the identification of different development mutants. Taking into account that progenies from the lines are being obtained and that the collection of T-DNA lines is going to enlarge progressively due to the high transformation efficiency achieved, there are great possibilities for identifying key genes involved in different tolerance mechanisms to salinity and drought.
[Show abstract][Hide abstract] ABSTRACT: Powdery mildew caused by Podosphaera xanthii is a major disease in melon crops, and races 1, 2, and 5 of this fungus are those that occur most frequently in southern Europe. The genotype TGR-1551 bears a dominant gene that provides resistance to these three races of P. xanthii. By combining bulked segregant analysis and amplified fragment length polymorphisms (AFLP), we identified eight markers linked to this dominant gene. Cloning and sequencing of the selected AFLP fragments allowed the development of six codominant PCR-based markers which mapped on the linkage group (LG) V. Sequence analysis of these markers led to the identification of two resistance-like genes, MRGH5 and MRGH63, belonging to the nucleotide binding site (NBS)-leucine-rich repeat (LRR) gene family. Quantitative trait loci (QTL) analysis detected two QTLs, Pm-R1-2 and Pm-R5, the former significantly associated with the resistance to races 1 and 2 (LOD score of 26.5 and 33.3; 53.6 and 61.9% of phenotypic variation, respectively), and the latter with resistance to race 5 (LOD score of 36.8; 65.5% of phenotypic variation), which have been found to be colocalized with the MRGH5 and MRGH63 genes, respectively. The results suggest that the cluster of NBS-LRR genes identified in LG V harbours candidate genes for resistance to races 1, 2, and 5 of P. xanthii. The evaluation of other resistant germplasm showed that the codominant markers here reported are also linked to the Pm-w resistance gene carried by the accession 'WMR-29' proving their usefulness as genotyping tools in melon breeding programmes.
Theoretical and Applied Genetics 03/2011; 122(4):747-58. · 3.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Muscari comosum L. (Liliaceae) displays a striking chromosomal polymorphism in the second largest chromosome. This polymorphism involves four cosmopolitan types. Two of these are shorter than the other two homologues. One of these is submetacentric (SSM) and the other is subtelocentric (SST). The two longer types also include a submetacentric (LSM) and a subtelocentric (LST) morph. Each of the two submetacentric chromosomes has one interstitial C-band in the short arm and each of the two subtelocentric morphs has an interstitial C-band in the long arm. The change of position of this interstitial C-band is most easily explained by a pericentric inversion. Furthermore, all four types of chromosome 2 have a centromeric C-band, while the two subtelocentrics have an additional terminal C-band in the long arm. The variability in the size of the second chromosome is most likely the consequence of an unequal interchange or an insertional translocation. The meiotic behaviour of the chromosome 2 bivalents in individuals heterozygous for the pericentric inversion is characterized by normal pairing between homologues with no inversion loops, though asynapsis was present in some meiocytes. Chiasmata are absent in two regions of chromosome 2 bivalents in these heterozygotes in which they regularly form in both classes of homozygotes. In individuals heterozygous for the long morphs of chromosome 2 the bivalents again showed normal pairing at pachytene, with chiasmata again absent in some regions in which they normally form. The net result is that homozygotes have significantly higher chiasmata frequencies than hterozygotes.
[Show abstract][Hide abstract] ABSTRACT: One hundred bulbs of Ornithogalum umbellatum L. have been analyzed cytogenetically in one natural population collected from the Sierra Nevada of Spain. Three types of plants were identified: (i) diploid plants (2n = 18, 26%); (ii) diploid plants with a variable number of B chromosomes (1–8 B's, 40%); and (iii) polysomic plants (2n = 19–23) with or without B's (34%). B's are of two types: metacentric and acrocentric and are associated with three types of abnormalities: (i) failure of the A chromosomes to move to the poles at anaphase I; (ii) nondisjunction of some A chromosomes at anaphase II; and (iii) the occurrence of tetraploid sporocytes. The B's are isopycnotic, do not associate with the A's, and invariably occur as univalents at first meiosis but show no tendency for elimination. All members of the complement except the satellite chromosome, no. 6, have been detected in a trisomic or a tetrasomic condition. Additionally some unusual structural variants, not present in the diploid standard complement, appear in some polysomic individuals. The polysomic elements are euchromatic, stable, and they do not associate either with normal chromosomes or with B's. The polysomic elements form univalents when they are trisomic and bivalents when tetrasomic. The fact that a high frequency (94%) of the polysomic elements also carry B's suggests that these two forms of numerical variation are interrelated in origin.
[Show abstract][Hide abstract] ABSTRACT: Some meiotic abnormalities, such as univalent formation, side-arm bridges, and bridges with fragments, were observed during both meiotic divisions in some individuals of Muscari comosum L. from one Spanish population. The latter aberrations were also detected during mitotic divisions. The majority of these abnormalities involved the first long pair of chromosomes. The exact nature of sister chromatid bridges has still not been elucidated. U-type exchanges can be explained on the basis of abnormal breakage and reunion occurring in the euchromatin that is near the heterochromatin present in the interstitial region of the long arm of the first bivalent. In accordance with the last aspect, there is no correlation between the distribution pattern of chiasmata within the first bivalent and the meiotic U-type exchanges. Spontaneous breakage and reunion events produce new combinations of chromosome segments in the first pair of chromosomes of M. comosum, and hence have been important from an evolutionary point of view in the origin of chromosome polymorphisms in this plant species.Key words: Muscari comosum, meiosis, side-arm bridges, U-type exchanges, chiasmata distribution.
[Show abstract][Hide abstract] ABSTRACT: Muscari comosum L. and Muscari matritensis Ruiz Rejón et al. are two closely related species of the subgenus Leopoldia, belonging to the genus Muscari (Liliaceae). Cytogenetic analyses have been made to analyse the differences between these species. Major differences are that M. comosum has four or five dark intercalary 4,6-diamidino-2-phenylindole (DAPI) positive C-bands in the first chromosome pair, whereas M. matritensis has only three thin bands. Muscari comosum has a large chromomycin A3 positive C-band in the fifth, nucleolus organizing region (NOR) bearing chromosome pair, whereas M. matritensis has the CMA3-positive band and the NOR in the short arm of the second pair. The possible role played by occurrences of translocations and amplifications in the chromosomal evolution of these species is discussed.Key words: Muscari, Liliaceae, karyotypes, evolution.
[Show abstract][Hide abstract] ABSTRACT: A reciprocal translocation was found with a high frequency (average 44.44%) in four natural populations of Allium paniculatum L. (Liliaceae) from the South of Spain. The chromosomes involved are 1 and 7. The translocation is reciprocal and unequal. Chiasma frequency in the chromosomes not involved in the interchange is not affected, but chiasma frequency is decreased in the translocated chromosomes in the heterozygotes. As a satellite chromosome is involved in the interchange, the nucleolus is associated with the quadrivalent and the pattern of nucleolus formation is changed in heterozygotes, which have a lower mean number of nucleoli than homozygous standard individuals . The spontaneous mutation rate for interchanges during the early stages of microsporogenesis is high (μ = 1.08 × 10−2). No interchange homozygotes were found in any of the four populations analyzed. Furthermore, a comparative analysis of heterozygous (HT) and homozygous standard (HM) individuals in two populations demonstrated that homozygous standard plants show, on the whole, higher fitness than the heterozygotes. This can be attributed to a greater egg cell fertility and seed set. The possible causes of maintenance are discussed: the interchange in A. paniculatum is probably not maintained by overdominance for generative reproductive characters, nor by a mutation–selection equilibrium. One possibility, that heterozygotes have superior vegetative reproduction, still remains open for future investigation.Key words: Allium paniculatum, interchange polymorphism, fitness.
Canadian Journal of Genetics and Cytology. 01/2011; 28(3):348-357.
[Show abstract][Hide abstract] ABSTRACT: Powdery mildew caused by Podosphaera xanthii has become a major problem in melon since it occurs all year round irrespective of the growing system. The TGR-1551 melon
genotype was found to be resistant to several melon diseases, among them powdery mildew. However, the corresponding resistance
genes have been never mapped. We constructed an integrated genetic linkage map using an F2 population derived from a cross
between the multi-resistant genotype TGR-1551 and the susceptible Spanish cultivar ‘Bola de Oro’. The map spans 1,284.9cM,
with an average distance of 3.6cM among markers, and consists of 354 loci (188 AFLP, 39 RAPD, 111 SSR, 14 SCAR/CAPS/dCAPS,
and two phenotypic traits) distributed in 14 linkage groups. QTL analysis identified one major QTL (Pm-R) on LG V for resistance to races 1, 2, and 5 of powdery mildew. The PM4-CAPS marker is closely linked to the Pm-R QTL at a genetic distance of 1.9cM, and the PM3-CAPS marker is located within the support interval of this QTL. These codominant
markers, together with the map information reported here, could be used for melon breeding, and particularly for genotyping
selection of resistance to powdery mildew in this vegetable crop species.
KeywordsCodominant DNA markers–Disease resistance–
–Quantitative trait loci
[Show abstract][Hide abstract] ABSTRACT: The genetic and phenotypic characterization of a new tomato (Solanum lycopersicum) insertional mutant, Arlequin (Alq) is reported. Alq mutant plants were affected in reproductive development and their sepals were homeotically converted into fleshy fruit-like organs. Molecular analysis demonstrated that a single copy of T-DNA was present in the mutant genome while genetic analysis confirmed that the mutant phenotype co-segregated with the T-DNA insertion and was inherited as a monogenic semi-dominant trait. The histological and scanning electron microscope analyses revealed cell identity changes in both external and internal tissues of Alq sepals. Flowers developed by Alq homozygous plants showed a severe mutant phenotype, since after fruit set, not only did the sepals become succulent but they also followed a ripening pattern similar to that of normal fruits. From a metabolic viewpoint, Alq sepals also behaved like a fruit, as they acquired the properties of a sink that acted alternatively and independently to the fruit. In fact, expression of regulatory genes controlling tomato fruit ripening was detected in Alq sepals at similar levels to those observed in mature fruits. Furthermore, the Alq mutation inhibited the development of the abscission zone in tomato flowers indicating that the JOINTLESS gene is regulated by ALQ. Results from the genetic and developmental characterization of the Alq tomato mutant suggest that the ALQ gene participates in the regulatory pathway controlling fruit ripening of tomato.
Plant and Cell Physiology 03/2010; 51(3):435-47. · 4.98 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Reproductive development of higher plants comprises successive events of organ differentiation and growth which finally lead to the formation of a mature fruit. However, most of the genetic and molecular mechanisms which coordinate such developmental events are yet to be identified and characterized. Arlequin (Alq), a semi-dominant T-DNA tomato mutant showed developmental changes affecting flower and fruit ripening. Sepals were converted into fleshy organs which ripened as normal fruit organs and fruits displayed altered ripening features. Molecular characterization of the tagged gene demonstrated that it corresponded to the previously reported tomato Agamous-like 1 (TAGL1) gene, the tomato ortholog of shatterproof MADS-box genes of Arabidopsis thaliana, and that the Alq mutation promoted a gain-of-function phenotype caused by the ectopic expression of TAGL1. Ectopic overexpression of TAGL1 resulted in homeotic alterations affecting floral organ identity that were similar to but stronger than those observed in Alq mutant plants. Interestingly, TAGL1 RNAi plants yielded tomato fruits which were unable to ripen. They displayed a yellow-orange color and stiffness appearance which are in accordance with reduced lycopene and ethylene levels, respectively. Moreover, pericarp cells of TAGL1 RNAi fruits showed altered cellular and structural properties which correlated to both decreased expression of genes regulating cell division and lignin biosynthesis. Over-expression of TAGL1 is able to rescue the non-ripening phenotype of rin and nor mutants, which is mediated by the transcriptional activation of several ripening genes. Our results demonstrated that TAGL1 participates in the genetic control of flower and fruit development of tomato plants. Furthermore, gene silencing and over-expression experiments demonstrated that the fruit ripening process requires the regulatory activity of TAGL1. Therefore, TAGL1 could act as a linking factor connecting successive stages of reproductive development, from flower development to fruit maturation, allowing this complex process to be carried out successfully.
PLoS ONE 01/2010; 5(12):e14427. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Besides being an important commercial crop, tomato (Solanum lycopersicum L.) constitutes a model species for the study of plant developmental processes. Current research tends to combine classic disciplines such as physiology and genetics with modern approaches coming from molecular biology and genomics with a view to elucidating the biological mechanisms underlying plant architecture, floral transition and development of flowers and fruits. Comparative and functional analyses of tomato regulatory genes such as LATERAL SUPPRESSOR (LS), SELF PRUNING (SP), SINGLE FLOWER TRUSS (SFT) and FALSIFLORA (FA) have revealed mechanisms involved in shoot development and flowering time which are conserved among Arabidopsis, tomato and other plant species. Furthermore, several regulatory genes encoding transcription factors have been characterized as responsible for singular features of vegetative and reproductive development of tomato. Thus, the sympodial growth habit seems to require a specific control of the developmental fate followed by shoot meristems. In this process, novel genetic and molecular interactions involving SP, SFT and FA genes would be essential. Also this latter, but mainly ANANTHA (AN) and COMPOUND INFLORESCENCE (S) have recently been found to regulate the inflorescence architecture of the tomato. Concerning fruit development, genetic and molecular analyses of new genes such as fw2.2, FASCIATED, OVATE and SUN have proved their contribution to the domestication process and most importantly, their function as key regulators of fruit size and shape variation. Tomato ripening is also being elucidated thanks to the characterization of regulatory genes such as RIPENING INHIBITOR (RIN), NON-RIPENING (NOR), TDR4 and COLORLESS NON-RIPENING (CNR), which have been found to control early stages of fruit development and maturation. At the same time, much research is dedicated to isolating the targets of the ripening regulators, as well as the key genes promoting the parthenocarpic development of tomato fruits. Hopefully, the ongoing sequencing project and the progress made by integrating several research fields will help to unravel the genetic and molecular pathways controlling tomato development.
The International journal of developmental biology 10/2009; 53(8-10):1635-48. · 2.16 Impact Factor