Screening And Functional Verification Of Stress Resistance Genes In Medicago Ruthenica Under Drought Stress And Rehydration

Medicago ruthenica is a good gene resource for improving the stress resistance of alfalfa and other forage.Mining resistance genes in Medicago ruthenica by RNA-Seq and import it into other pastures was benefit for obtaining the improvement effect in a short time.Therefore,the research and utilization of stress resistance genes of Medicago ruthenica is of great significance to the genetic improvement of alfalfa.The experiment aims to study the variations of morphology,physiology and molecular level of Medicago ruthenica(L.)cv.Zhilixing under low water potentials.And explored the response and adaptive mechanism of Medicago ruthenica ‘Zhilixing’ in drought stress preliminarily.At the same time,we screened the drought resistance genes in it and verified their functions by genetic transformation.It lays a foundation for the innovation and utilization of molecular breeding.Main results of this study were as follows:(1)Stomatal parameters,physiological and biomass distribution patterns of Medicago ruthenica ‘Zhilixing’ leaves were all responded to drought stress.After rewatering,all indexes could basically recover.Medicago ruthenica ‘Zhilixing’ showed strong drought resistance and stage adaptation.(2)2,905 DEGs that responded to drought stress and rewatering were screened out from transcriptome data of Medicago ruthenica ‘Zhilixing’.Under drought stress,DEGs were mainly enriched in carbohydrate metabolism,amino acid metabolism and photosynthesis related metabolic pathways.After rehydration,DEGs were mainly enriched in carbohydrate metabolism,amino acid metabolism,flavonoid biosynthesis and so on.Its enrichment indicated that Medicago ruthenica ‘Zhilixing’ adopts different strategies to adapt to drought stress and rehydration.(3)Not only the stress resistance but also the biomass and seeds yield of tobacco overexpressing Mr ERF,Mrb ZIP and Mr SURNod genes were better than those of wild type.And the transgenic plants had early flowered and short growth period,which might be one of the ways to deal with adversity stress.(4)Mr ERF,Mrb ZIP and Mr SURNod genes of Medicago ruthenica were beneficial to the development of root.Mr ERF and Mrb ZIP could increase the number of lateral roots as well as the elongation of main roots,while Mr SURNod could promote the elongation of tobacco roots.And such root characteristics increased the plant height and biomass of transgenic tobacco.(5)Mr ERF and Mrb ZIP were positive regulators in response to drought and salt stress,while Mr SURNod was a positive regulator in response to drought and low temperature stress.In conclusion,Medicago ruthenica adapts to different degrees of drought stress and rewatering in different ways.Mr ERF,Mrb ZIP and Mr SURNod are conducive to improving the stress resistance of plants,among which Mr ERF has the best effect.