[Show abstract][Hide abstract] ABSTRACT: Among a set of genes in pea (Pisum sativum L.) that were induced under drought-stress growth conditions, one encoded a protein with significant similarity to a regulator of chlorophyll catabolism, SGR. This gene, SGRL, is distinct from SGR in genomic location, encoded carboxy-terminal motif, and expression through plant and seed development. Divergence of the two encoded proteins is associated with a loss of similarity in intron/exon gene structure. Transient expression of SGRL in leaves of Nicotianabenthamiana promoted the degradation of chlorophyll, in a manner that was distinct from that shown by SGR. Removal of a predicted transmembrane domain from SGRL reduced its activity in transient expression assays, although variants with and without this domain reduced SGR-induced chlorophyll degradation, indicating that the effects of the two proteins are not additive. The combined data suggest that the function of SGRL during growth and development is in chlorophyll re-cycling, and its mode of action is distinct from that of SGR. Studies of pea sgrL mutants revealed that plants had significantly lower stature and yield, a likely consequence of reduced photosynthetic efficiencies in mutant compared with control plants under conditions of high light intensity.
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[Show abstract][Hide abstract] ABSTRACT: A fast neutron (FN)-mutagenised population was generated in Pisum sativum L. (pea) to enable the identification and isolation of genes underlying traits and processes. Studies of several phenotypic traits have clearly demonstrated the utility of the resource by associating gene deletions with phenotype followed by functional tests exploiting additional mutant sources, from both induced and natural variant germplasm. For forward genetic screens, next generation sequencing methodologies provide an opportunity for identifying genes associated with deletions rapidly and systematically. The application of rapid reverse genetic screens of the fast neutron mutant pea population supports conclusions on the frequency of deletions based on phenotype alone. These studies also suggest that large deletions affecting one or more loci can be non-deleterious to the pea genome, yielding mutants that could not be obtained by other means. Deletion mutants affecting genes associated with seed metabolism and storage are providing unique opportunities to identify the products of complex and related gene families, and to study the downstream consequences of such deletions.
Full-text · Article · Aug 2013 · Functional Plant Biology
[Show abstract][Hide abstract] ABSTRACT: Plants exhibit various kinds of movements that have fascinated scientists and the public for centuries. Physiological studies in plants with the so-called motor organ or pulvinus suggest that cells at opposite sides of the pulvinus mediate leaf or leaflet movements by swelling and shrinking. How motor organ identity is determined is unknown. Using a genetic approach, we isolated a mutant designated elongated petiolule1 (elp1) from Medicago truncatula that fails to fold its leaflets in the dark due to loss of motor organs. Map-based cloning indicated that ELP1 encodes a putative plant-specific LOB domain transcription factor. RNA in situ analysis revealed that ELP1 is expressed in primordial cells that give rise to the motor organ. Ectopic expression of ELP1 resulted in dwarf plants with petioles and rachises reduced in length, and the epidermal cells gained characteristics of motor organ epidermal cells. By identifying ELP1 orthologs from other legume species, namely pea (Pisum sativum) and Lotus japonicus, we show that this motor organ identity is regulated by a conserved molecular mechanism.
Full-text · Article · Jun 2012 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: The inheritance of flower color in pea (Pisum sativum) has been studied for more than a century, but many of the genes corresponding to these classical loci remain unidentified. Anthocyanins are the main flower pigments in pea. These are generated via the flavonoid biosynthetic pathway, which has been studied in detail and is well conserved among higher plants. A previous proposal that the Clariroseus (B) gene of pea controls hydroxylation at the 5' position of the B ring of flavonoid precursors of the anthocyanins suggested to us that the gene encoding flavonoid 3',5'-hydroxylase (F3'5'H), the enzyme that hydroxylates the 5' position of the B ring, was a good candidate for B. In order to test this hypothesis, we examined mutants generated by fast neutron bombardment. We found allelic pink-flowered b mutant lines that carried a variety of lesions in an F3'5'H gene, including complete gene deletions. The b mutants lacked glycosylated delphinidin and petunidin, the major pigments present in the progenitor purple-flowered wild-type pea. These results, combined with the finding that the F3'5'H gene cosegregates with b in a genetic mapping population, strongly support our hypothesis that the B gene of pea corresponds to a F3'5'H gene. The molecular characterization of genes involved in pigmentation in pea provides valuable anchor markers for comparative legume genomics and will help to identify differences in anthocyanin biosynthesis that lead to variation in pigmentation among legume species.
[Show abstract][Hide abstract] ABSTRACT: Genetic variation at the Tri locus, controlling seed trypsin inhibitor activity, is relevant to both food and feed uses of Pisum sativum L. (pea). Near-isogenic lines of Pisum sativum L. (pea) were developed previously to examine the impact on digestibility of variation at Tri on linkage group V. Further studies of these lines have now revealed a significant difference in seed nitrogen concentration
between near-isolines having contrasting seed trypsin inhibitor activity. In order to investigate this apparent association,
the multiple genes at a closely linked locus, Vc-2, encoding a set of major vicilin polypeptides, were analysed and shown to differ between the near-isolines. Characterisation
of Vc-2 cDNAs revealed distinguishing features of the functional genes between the parents of the near-isolines, while analyses of
gene structure showed that a disrupted variant Vc-2 gene was present in one, but not the second, parent of the near-isolines. The variant gene appeared to be non-functional,
based both on its deduced truncated protein lacking part of one conserved cupin structural domain, and the fact that it did
not correspond to any isolated cDNA. Recombinant near-isolines were generated between the closely linked Tri and Vc-2 loci to investigate the genetic association with seed nitrogen concentration. Seeds from near-isolines and recombinant inbred
lines where the variant Vc-2 gene was present had lower seed nitrogen concentration than lines lacking the variant gene. Furthermore, the disrupted Vc-2 gene was absent from several pea genotypes with high seed protein content. Expression analyses suggested that gene expression
at the Vc-2 locus was higher when the non-functional gene variant was absent. Markers based either on the element which disrupts the
coding sequence within the variant gene at the Vc-2 locus, or on the closely linked Tri locus, may be exploited in the selection of haplotypes associated with genetic variation in seed protein composition and
concentration. The gene content in the genomic region of Medicago truncatula chromosome 7 that is syntenic with the pea linkage group V has identified further candidates for functional analyses and
marker assisted selection.
Pisum sativum L.–Seed protein–
[Show abstract][Hide abstract] ABSTRACT: The genetic regulation of flower color has been widely studied, notably as a character used by Mendel and his predecessors in the study of inheritance in pea.
We used the genome sequence of model legumes, together with their known synteny to the pea genome to identify candidate genes for the A and A2 loci in pea. We then used a combination of genetic mapping, fast neutron mutant analysis, allelic diversity, transcript quantification and transient expression complementation studies to confirm the identity of the candidates.
We have identified the pea genes A and A2. A is the factor determining anthocyanin pigmentation in pea that was used by Gregor Mendel 150 years ago in his study of inheritance. The A gene encodes a bHLH transcription factor. The white flowered mutant allele most likely used by Mendel is a simple G to A transition in a splice donor site that leads to a mis-spliced mRNA with a premature stop codon, and we have identified a second rare mutant allele. The A2 gene encodes a WD40 protein that is part of an evolutionarily conserved regulatory complex.
[Show abstract][Hide abstract] ABSTRACT: Dense genetic maps, together with the efficiency and accuracy of their construction, are integral to genetic studies and marker assisted selection for plant breeding. High-throughput multiplex markers that are robust and reproducible can contribute to both efficiency and accuracy. Multiplex markers are often dominant and so have low information content, this coupled with the pressure to find alternatives to radio-labelling, has led us to adapt the SSAP (sequence specific amplified polymorphism) marker method from a 33P labelling procedure to fluorescently tagged markers analysed from an automated ABI 3730 xl platform. This method is illustrated for multiplexed SSAP markers based on retrotransposon insertions of pea and is applicable for the rapid and efficient generation of markers from genomes where repetitive element sequence information is available for primer design. We crossreference SSAP markers previously generated using the 33P manual PAGE system to fluorescent peaks, and use these high-throughput fluorescent SSAP markers for further genetic studies in Pisum.
[Show abstract][Hide abstract] ABSTRACT: Tendrils are contact-sensitive, filamentous organs that permit climbing plants to tether to their taller neighbors. Tendrilled legume species are grown as field crops, where the tendrils contribute to the physical support of the crop prior to harvest. The homeotic tendril-less (tl) mutation in garden pea (Pisum sativum), identified almost a century ago, transforms tendrils into leaflets. In this study, we used a systematic marker screen of fast neutron-generated tl deletion mutants to identify Tl as a Class I homeodomain leucine zipper (HDZIP) transcription factor. We confirmed the tendril-less phenotype as loss of function by targeting induced local lesions in genomes (TILLING) in garden pea and by analysis of the tendril-less phenotype of the t mutant in sweet pea (Lathyrus odoratus). The conversion of tendrils into leaflets in both mutants demonstrates that the pea tendril is a modified leaflet, inhibited from completing laminar development by Tl. We provide evidence to show that lamina inhibition requires Unifoliata/LEAFY-mediated Tl expression in organs emerging in the distal region of the leaf primordium. Phylogenetic analyses show that Tl is an unusual Class I HDZIP protein and that tendrils evolved either once or twice in Papilionoid legumes. We suggest that tendrils arose in the Fabeae clade of Papilionoid legumes through acquisition of the Tl gene.