[Show abstract][Hide abstract] ABSTRACT: Inflorescence development is a key factor of plant productivity, as it determines flower number. Therefore, understanding the mechanisms that regulate inflorescence architecture is critical for reproductive success and crop yield. In this study, a new mutant, vegetative inflorescence (mc-vin), was isolated from the screening of a tomato (Solanum lycopersicum L.) T-DNA mutant collection. The mc-vin mutant developed inflorescences that reverted to vegetative growth after forming two to three flowers, indicating that the mutated gene is essential for the maintenance of inflorescence meristem identity. The T-DNA was inserted into the promoter region of the MACROCALYX (MC) gene; this result together with complementation test and expression analyses proved that mc-vin is a new knock-out allele of MC. Double combinations between mc-vin and jointless (j) and single flower truss (sft) inflorescence mutants showed that MC has pleiotropic effects on the reproductive phase, and that it interacts with SFT and J to control floral transition and inflorescence fate in tomato. In addition, MC expression was mis-regulated in j and sft mutants whereas J and SFT were significantly up-regulated in the mc-vin mutant. Together, these results provide new evidences about MC function as part of the genetic network regulating the development of tomato inflorescence meristem.
Full-text · Article · Jan 2016 · Scientific Reports
[Show abstract][Hide abstract] ABSTRACT: A screening under salt stress conditions of a T-DNA mutant collection of tomato (Solanum lycopersicum L.) led to the identification of the altered response to salt stress 1 (ars1) mutant, which showed a salt-sensitive phenotype. Genetic analysis of the ars1 mutation revealed that a single T-DNA insertion in the ARS1 gene was responsible of the mutant phenotype. ARS1 coded for an R1-MYB type transcription factor and its expression was induced by salinity in leaves. The mutant reduced fruit yield under salt acclimation while in the absence of stress the disruption of ARS1 did not affect this agronomic trait. The stomatal behaviour of ars1 mutant leaves induced higher Na(+) accumulation via the transpiration stream, as the decreases of stomatal conductance and transpiration rate induced by salt stress were markedly lower in the mutant plants. Moreover, the mutation affected stomatal closure in a response mediated by abscisic acid (ABA). The characterization of tomato transgenic lines silencing and overexpressing ARS1 corroborates the role of the gene in regulating the water loss via transpiration under salinity. Together, our results show that ARS1 tomato gene contributes to reduce transpirational water loss under salt stress. Finally, this gene could be interesting for tomato molecular breeding, because its manipulation could lead to improved stress tolerance without yield penalty under optimal culture conditions.
Full-text · Article · Nov 2015 · Plant Biotechnology Journal
[Show abstract][Hide abstract] ABSTRACT: QTL and candidate genes associated to fruit quality traits have been identified in a tomato genetic map derived from Solanum pimpinellifolium L., providing molecular tools for marker-assisted breeding. The study of genetic, physiological, and molecular pathways involved in fruit development and ripening has considered tomato as the model fleshy-fruited species par excellence. Fruit quality traits regarding organoleptic and nutritional properties are major goals for tomato breeding programs since they largely decide the acceptance of tomato in both fresh and processing markets. Here we report the genetic mapping of single-locus and epistatic quantitative trait loci (QTL) associated to the fruit size and content of sugars, acids, vitamins, and carotenoids from the characterization of a RIL population derived from the wild-relative Solanum pimpinellifolium TO-937. A genetic map composed of 353 molecular markers including 13 genes regulating fruit and developmental traits was generated, which spanned 1007 cM with an average distance between markers of 2.8 cM. Genetic analyses indicated that fruit quality traits analyzed in this work exhibited transgressive segregation and that additive and epistatic effects are the major genetic basis of fruit quality traits. Moreover, most mapped QTL showed environment interaction effects. FrW7.1 fruit size QTL co-localized with QTL involved in soluble solid, vitamin C, and glucose contents, dry weight/fresh weight, and most importantly with the Sucrose Phosphate Synthase gene, suggesting that polymorphisms in this gene could influence genetic variation in several fruit quality traits. In addition, 1-deoxy-D-xylulose 5-phosphate synthase and Tocopherol cyclase genes were identified as candidate genes underlying QTL variation in beta-carotene and vitamin C. Together, our results provide useful genetic and molecular information regarding fruit quality and new chances for tomato breeding by implementing marker-assisted selection.
[Show abstract][Hide abstract] ABSTRACT: Colletotrichum lindemuthianum is a hemibiotrophic fungal pathogen that causes anthracnose disease in common bean. Despite the genetics of anthracnose resistance has been studied for a long time, few quantitative trait loci (QTLs) studies have been conducted on this species. The present work examines the genetic basis of quantitative resistance to races 23 and 1545 of C. lindemuthianum in different organs (stem, leaf and petiole). A population of 185 recombinant inbred lines (RIL) derived from the cross PMB0225 × PHA1037 was evaluated for anthracnose resistance under natural and artificial photoperiod growth conditions. Using multi-environment QTL mapping approach, 10 and 16 main effect QTLs were identified for resistance to anthracnose races 23 and 1545, respectively. The homologous genomic regions corresponding to 17 of the 26 main effect QTLs detected were positive for the presence of resistance-associated gene cluster encoding nucleotide-binding and leucine-rich repeat (NL) proteins. Among them, it is worth noting that the main effect QTLs detected on linkage group 05 for resistance to race 1545 in stem, petiole and leaf were located within a 1.2 Mb region. The NL gene Phvul.005G117900 is located in this region, which can be considered an important candidate gene for the non-organ-specific QTL identified here. Furthermore, a total of 39 epistatic QTL (E-QTLs) (21 for resistance to race 23 and 18 for resistance to race 1545) involved in 20 epistatic interactions (eleven and nine interactions for resistance to races 23 and 1545, respectively) were identified. None of the main and epistatic QTLs detected displayed significant environment interaction effects. The present research provides essential information not only for the better understanding of the plant-pathogen interaction but also for the application of genomic assisted breeding for anthracnose resistance improvement in common bean through application of marker-assisted selection (MAS).
Full-text · Article · Mar 2015 · Frontiers in Plant Science
[Show abstract][Hide abstract] ABSTRACT: Jasmonic acid (JA) regulates a wide spectrum of plant biological processes, from plant development to stress defense responses. The role of JA in plant response to salt stress is scarcely known, and even less known is the specific response in root, the main plant organ responsible for ionic uptake and transport to the shoot. Here we report the characterization of the first tomato (Solanum lycopersicum) mutant, named res (restored cell structure by salinity), that accumulates JA in roots prior to exposure to stress. The res tomato mutant presented remarkable growth inhibition and displayed important morphological alterations and cellular disorganization in roots and leaves under control conditions, while these alterations disappeared when the res mutant plants were grown under salt stress. Reciprocal grafting between res and wild type (WT) (tomato cv. Moneymaker) indicated that the main organ responsible for the development of alterations was the root. The JA-signaling pathway is activated in res roots prior to stress, with transcripts levels being even higher in control condition than in salinity. Future studies on this mutant will provide significant advances in the knowledge of JA role in root in salt stress tolerance response, as well as in the energy trade-off between plant growth and response to stress.
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Full-text · Article · Jan 2015 · Physiologia Plantarum
[Show abstract][Hide abstract] ABSTRACT: The common bean is the most relevant grain legume for direct human consumption. The current bean germplasm collections show a wide variation of phenotypes, although in many developed countries where landraces are being replaced by elite cultivars the genetic erosion is progressively affecting the species. This crop has expanded through all the continents during the past centuries, and bean germplasm out of its regions of origin is more complex than was previously thought and contains additional diversity that remains to be explored for its breeding value. The integration of genomic data into gene bank documentation systems and its combination with agronomic, genetic, phenotypic and ecological data will open a new era for the valorization of this grain legume.
[Show abstract][Hide abstract] ABSTRACT: A novel tomato (Solanum lycopersicum L.) mutant affected in reproductive development, excessive number of floral organs (eno), is described in this study. The eno plants yielded flowers with a higher number of floral organs in the three innermost floral whorls and larger fruits than those found in wild-type plants. Scanning-electron microscopy study indicated that the rise in floral organ number and fruit size correlates with an increased size of floral meristem at early developmental stages. It has been reported that mutation at the FASCIATED (FAS) gene causes the development of flowers with supernumerary organs; however, complementation test and genetic mapping analyses proved that ENO is not an allele of the FAS locus. Furthermore, expression of WUSCHEL (SlWUS) and INHIBITOR OF MERISTEM ACTIVITY (IMA), the two main regulators of floral meristem activity in tomato, is altered in eno but not in fas flowers indicating that ENO could exert its function in the floral meristem independently of FAS. Interestingly, the eno mutation delayed the expression of IMA leading to a prolonged expression of SlWUS, which would explain the greater size of floral meristem. Taken together, results showed that ENO plays a significant role in the genetic pathway regulating tomato floral meristem development.
[Show abstract][Hide abstract] ABSTRACT: Adaptation to the environment and reproduction are dependent on the date of flowering in the season. Despite the genetic and complexity and quantitative nature of flowering time, many genes regulating this trait has been molecular isolated and functional characterized in the model species Arabidopsis thaliana, even some of their homologues have also been identified in other legume species. However, regulatory genes involved in the transition to flowering have not been characterized so far in common bean (Phaseolus vulgaris L.). With this aim, we have evaluated the effect of photoperiod on flowering date of the legume species, Phaseolus vulgaris and described the genetic architecture of this trait. For this purpose, a mapping population of 185 recombinant inbred lines (RILs) derived from a cross between a temperate and a tropical inbred line was generated and grown under short-and long-day photoperiod conditions. Multi-environment QTL analyses for flowering date and photoperiod sensitivity were conducted; as result additive and additive-by-environment effects were found. In addition, additive-by-additive epistatic effects were detected by means of two-locus QTL analyses. Overall, the results obtained revealed that the genetics of flowering date and photoperiod sensitivity is complex in nature, where both individual additive and epistatic effects are important components of the genetic variance. By using these QTLs in a marker assisted-selection program, it would be possible to select for desirable photoperiod sensitivity alleles leading to better adapted common bean varieties. This work was partially financed by the MINECO (AGL2011-25562), Junta de Andalucía (P10-AGR-06931) and Campus de Excelencia Internacional Agroalimentario-CeiA3. J.J. Cruz and L. Godoy were recipients of fellowships from CONACYT and INIFAP from México and SENESCYT from Ecuador Governments, respectively. 62 Genomics and Genetics Saxena, R.K. Fast forward genetic mapping provide candidate genes for resistance to fusarium wilt and sterility mosaic disease resistance in pigeonpea (Cajanus cajan L. Millsp.) Fast forward genetic mapping provide candidate genes for resistance to fusarium wilt and sterility mosaic disease resistance in pigeonpea (Cajanus cajan L. Millsp.)
[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: 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.
Full-text · Article · Mar 2014 · Journal of Experimental Botany
[Show abstract][Hide abstract] ABSTRACT: Key message
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.
Full-text · Article · Jan 2014 · Theoretical and Applied Genetics
[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.
No preview · Article · Aug 2012 · Theoretical and Applied Genetics
[Show abstract][Hide abstract] ABSTRACT: Background
Nuña 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 nuña 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 nuña 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.
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.
The QTLs here reported constitute useful tools for marker assisted selection breeding programs aimed at improving nuña 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.
Full-text · Article · Aug 2012 · BMC Plant Biology