Functional Analysis Of Stress-Resistance Genes LcLycE And LcF3H And Senescence-Associated Gene SAG172

Further increasing the yield of crops is a major challenge of modern agriculture research with a growing world population. Abiotic stresses and premature senescence are major reasons that affect the growth and development of plants, leading to decrease survive rate and reduce crop yield around the world.Over the course of evolution, plants have developed enormous molecular mechanisms to adapt to the reverse environment; for example, plants can produce many secondary metabolites such as phenolic and terpenoids compounds to resist abiotic stress. It is well known that carotenoids and flavonoids can contribute to eliminate reactive oxygen, conferring stress tolerance in plants. In this study, two key genes including lycopene ?-cyclase and flavanone 3-hydroxylase were isolated from Lycium chinensis, which function in carotenoid and flavonoid biosynthetic pathway,respectively. We registered these two genes as LcLycE and LcF3H. Color complementation analysis identified LcLycE could catalyze lycopene to a-carotene.qPCR showed LcLycE gene was induced by chilling stress,which hint this gene involved in regulation of chilling stress resistance. Overexpressing LcLycE gene in tobacco could improve lutein content and increase NPQ and weaken photo-inhibition,which contributed to chilling-resistance. TLC experiment showed that LcF3H could hydroxylate NAR to DHK. qPCR analysis revealed that LcF3H gene expression level was induced under drought stress, which suggested a speculated function with regulating drought-resistance. The overexpression of LcF3H enhanced the content of flavan-3-ols in transgenics, leading to the improvement of the antioxidant system and elimination of ROS, which devoted to the tolerance to drought stress.Leaf senesce is the final stage of leaf development, early senescence of leaves has significant effects on the fruits size and yield traits during the later growth stages.Therefore, to fully explore the regulatory mechanism of leaf senescence will be of great importance in increasing crop yield and quality. One senescence-associated LRR-RLK gene, SAG172, was identified in this study. The sag 172 mutant lines showed a delayed leaf senescence phenotype and less water loss compared with WT.Meanwhile,inducible overexpressed SAG172 lines showed premature senescence and much water loss and decreased ABA sensibility of stoma movement. These results showed SAG172 could promote leaf senescence by regulating stoma movement and water loss. qPCR analysis and GUS reporter system revealed that SAG 172 was induced by senescence and ABA, and which was co-inducible with AtNAP transcription factor. The result suggested a possible regulatory relationship between these two genes. Yeast one-hybrid and GUS activity analysis showed SAG172 was directed by AtNAP transcription factor.sag172 mutant lines were sensitive with ABA but no obvious differences found when treated with JA, ETH and SA. qPCR analysis showed that ABA inducible marker genes were down-regulated in sag] 72 mutants.These results suggest that the regulatory mechanism of leaf senescence by SAG 172 through ABA signal pathway.Collectively, the study of LcLycE, LcF3H and SAG 172 make contribution to molecular breeding about stress-resistance, delaying crop senescence and improving yield.