The Diversity Of Genes Related Proline Accumulation And Association With Seedling Salt Tolerance In Rice

Soil salinity is one of the major stresses that limit crop growth and productivity. It is therefore imperative to study the genetic mechanism of salt tolerance in rice, to identify new tolerant genes, and to breed cultivars with tolerance to salt stress.In this study, we sequenced and analyzed the nucleotide diversity of proline accumulation related genes, OsP5CS1,OsP5CS2,OsP5CR and OsProDH, in a mini-core collection of rice in China. Meanwhile,96 accessions were cultivated under normal and 200 mM NaCl stress conditions to investigate their seedling height, root fresh weight, root dry weight, shoot fresh weight, shoot dry weight, score of salt toxicity and proline content of leaf at seedling stage. We then analyzed the associations between the gene diversity and these traits.The main results are as follows:1.Under normal and 200 mM NaCl stress conditions, seedling height, root fresh weight, root dry weight, shoot fresh weight, shoot dry weight, score of salt toxicity and proline content of leaf at seedling stage displayed approximately normal distribution, indicating that all of these traits are quantitative traits controlled by multiple genes.2.The coefficient of variation (CV) of proline content of leaf was the biggest one (CV=61.0%) among all the traits under the 200 mM NaCl condition. The result indicated that proline content of leaf can be used as salt tolerance index to reflect the differences that exsited in various varieties.3.Except for proline content of leaf, other traits under normal condition were significant correlation with its measurement under salt stress condition. Significant negative correlation between relative root fresh/dry weight and its measurement under normal condition suggested a trend that better performance of variety, lower tolerance to the stress.4. The nucleotide diversity in OsProDH was the highest (Ï€=0.01034) among the four proline accumulation related genes.Neutrality tests showed that a significant deviation from the neutral expectation in 5'-UTR and 3'-UTR of OsP5CS1 and 3'-UTR of OsP5CS2.The result indicated that OsP5CS1 and OsP5CS2 were under selection pressure during rice evolution.5.The polymorphism sites of OsP5CS1,OsP5CS2 and OsP5CR associated with different relative salt tolerance indexes, explained 4.1% to 11.8% of the variations. The site+1322 in the intron 4th of OsP5CR could explained 11.8% of the variation of relative plant fresh weight; this site also correlated with proline content under the 200 mM NaCl condition, and could explained 4.2% of the variation; this site also could explained 10.6% of the variation of score of salt toxicity; the sites +1445 in the same region was found to be correlated with relative proline content, could explained 3.9% of the variation.