The Function Study Of Circadian Clock Gene MtLHY In Medicago Truncatula About Salt Tolerance

The circadian clock integrates environmental signals and internal cues to coordinate the survival and reproduction of plants under a variety of harsh environments.The LATE ELONGATED HYPOCOTYL(LHY),a vital clock component,is required for flowering time,hypocotyl elongation,nodulation in legumes,and abiotic stress.Nevertheless,the roles of LHY in abiotic stress of Medicago truncatula are largely uncharacterized.In the previous work,we screened mtlhy mutant plants and obtained 35S:MtLHY plants.Under salt stress,the transcript level of MtLHY was significantly increased.Through salt treatment,mtlhy mutant plants were more sensitive to salt stress,while 35S:MtLHY plants were salt-tolerant,which showed that MtLHY plays an active role in salt stress.and compared with WT,mtlhy mutant plants had shorter root lengths,the germination rate of seeds decreased and accumulated more reactive oxygen species.35S:MtLHY plants had longer root lengths and less reactive oxygen species accumulation.Under salt stress,the transcript levels of genes of the flavonoid synthesis pathway had significant differences in mtlhy mutant plants and 35S:MtLHYplants,especially the flavonol synthesis gene FLA VONOL SYNTHASE(FLS),which was upregulated more than 20 times in 35S:MtLHY plants.Through the Yeast-one-hybrid assays and Transient expression assays in tobacco,we found that MtLHY could bind the promoter of MtFLS to activate its expression,leading to the accumulation of flavonol in plants.In brief,our results illustrated that MtLHY confers salt tolerance in M.truncatula by orchestrating flavonoid signaling.In addition,because of the close homologous between M.truncatula and Medicago sativa,our results also provided a new theoretical basis for the development of M.sativa.