Leveraging barrel medic genome sequence for the development and use of genomic resources for genetic analysis and breeding in legumes

BACKGROUND: A total of 62,591 cowpea expressed sequence tags (ESTs) were BLAST aligned to the whole-genome sequence of barrel medic (Medicago truncatula) to develop conserved intron scanning primers (CISPs). The efficacy of the primers was tested across 10 different legumes and on different varieties of cowpea, chickpea, and pigeon pea. Genetic diversity was assessed using the same primers on different cowpea genotypes. Singlenucleotide polymorphisms (SNPs) were detected, which were later converted to length polymorphism markers for easy genotyping. CISPs developed in this study were used in tagging resistance to bacterial leaf blight disease in cowpea. RESULTS: A total of 1262 CISPs were designed. The single-copy amplification success rates using these primers on 10 different legumes and on different varieties of cowpea, chickpea, and pigeon pea were approximately 60% in most of the legumes except soybean (47%) and peanut (37%). Genetic diversity analysis of 35 cowpea genotypes using 179 CISPs revealed 123 polymorphic markers with PIC values ranging from 0.05 to 0.59. Potential SNPs identified in cowpea, chickpea, and pigeon pea were converted to PCR primers of various sizes for easy genotyping. Using the markers developed in this study, a genetic linkage map was constructed with 11 linkage groups in cowpea. QTL mapping with 194 F3 progeny families derived from the cross C-152 × V-16 resulted in the identification of three QTLs for resistance to bacterial leaf blight disease. Conclusions: CISPs were proved to be efficient markers to identify various other marker classes like SNPs through comparative genomic studies in lesser studied crops and to aid in systematic sampling of the entire genome for well-distributed markers at low cost

Low-temperature tolerance in land plants: Are transcript and membrane responses conserved?

Plants' tolerance of low temperatures is an economically and ecologically important limitation on geographic distributions and growing seasons. Tolerance for low temperatures varies significantly across different plant species, and different mechanisms likely act in different species. In order to survive low-temperature stress, plant membranes must maintain their fluidity in increasingly cold and oxidative cellular environments. The responses of different species to low-temperature stress include changes to the types and desaturation levels of membrane lipids, though the precise lipids affected tend to vary by species. Regulation of membrane dynamics and other low-temperature tolerance factors are controlled by both transcriptional and post-transcriptional mechanisms. Here, we review low-temperature induced changes in both membrane lipid composition and gene transcription across multiple related plant species with differing degrees of low-temperature tolerance. We attempt to define a core set of changes for transcripts and lipids across species and treatment variations. Some responses appear to be consistent across all species for which data are available, while many others appear likely to be species or family-specific. Potential rationales are presented, including variance in testing, reporting and the importance of considering the level of stress perceived by the plant.

Epigenomic plasticity of Arabidopsis msh1 mutants under prolonged cold stress.

Dynamic transcriptional and epigenetic changes enable rapid adaptive benefit to environmental fluctuations. However, the underlying mechanisms and the extent to which this occurs are not well known. MutS Homolog 1 (MSH1) mutants cause heritable developmental phenotypes accompanied by modulation of defense, phytohormone, stress-response, and circadian rhythm genes, as well as heritable changes in DNA methylation patterns. Consistent with gene expression changes, msh1 mutants display enhanced tolerance for abiotic stress including drought and salt stress, while showing increased susceptibility to freezing temperatures. Despite changes in defense and biotic stress-response genes, msh1 mutants showed increasing susceptibility to the bacterial pathogen Pseudomonas syringae. Our results suggest that chronic cold and low light stress (10°C, 150 µmol m-2 s-1) influences non-CG methylation to a greater degree in msh1 mutants compared to wild-type Col-0. Furthermore, CHG changes are more closely pericentromeric, whereas CHH changes are generally more dispersed. This increased variation in non-CG methylation pattern does not significantly affect the msh1-derived enhanced growth behavior after mutants are crossed with isogenic wild type, reiterating the importance of CG methylation changes in msh1-derived enhanced vigor. These results indicate that msh1methylome is hyper-responsive to environmental stress in a manner distinct from the wild-type response, but CG methylation changes are potentially responsible for growth vigor changes in the crossed progeny.