Study On The Mechanism Of 2,4-Epibrassinolide (EBR) Treatment To Improve Potato Drought Resistance

With the global warming,the shortage of water resources is increasingly prominent,and drought has become an important limiting factor in agricultural production.Potato（Solanum tuberosum L.）is an annual tuber plant of Solanaceae.The potato planting area in China is mainly distributed in arid and semi-arid areas,while potatoes are sensitive to water deficit.Therefore,it is of great value to study the physiological mechanism of drought resistance and to take measures to alleviate drought stress in potato production and cultivation.Brassinolide is used in this experiment because of it can be synthesized artificially with high activity and no toxic and side effects on plants.In this experiment,the medium drought-resistant potato variety‘Xuanshu No.2’was used as the material.At first,potato plants were sprayed with different concentrations（0μmol/L,0.125μmol/L,0.25μmol/L,0.5μmol/L,1μmol/L,2μmol/L）of 2,4-epibrassinolide and treated with natural drought to select for optimum EBR concentration for relieving drought stress.Then studied the changes of potato growth and photosynthetic indexes under drought stress by EBR treatment.The differentially expressed gene information was obtained by transcriptome sequencing,and the synthesis pathway of brassinolide and the expression of genes related to drought stress were analyzed to explore the response and regulation mechanism of brassinolide applied to potato under drought stress.Hope to provide an effective and convenient measure for potato to resist drought stress.The main results of this study are as follows:1.Under drought stress,the potato plants treated with 0.5μM EBR had the highest water content,the highest net photosynthetic,the lowest relative conductivity and the best growth state,which was the closest to the normal watering state.2.EBR treatment enhanced the drought tolerance of potato,delayed the increase of soluble sugar and proline content,the increase of chlorophyll and carotenoid content,and the degradation of soluble protein in the late stage of stress.EBR treatment also increased net photosynthetic rate,stomatal conductance,transpiration rate and leaf water content.keep Fm,Fv,qN at the same level as the control.It is also enhanced the activity of SOD,POD,reduced the accumulation of H₂O₂ and O₂^-.Reduced conductivity,reduced MDA content,increased ABA content.3.The four processed materials were sequenced by transcriptome.KEGG enrichment analysis showed that drought-treated differential genes enriched 6 metabolic pathways,and EBR-treated differential genes enriched 4 metabolic pathways.The differentially expressed genes in response to drought stress and brassinolide were enriched to five GO pathways.BCvsWC,BDvsBC,BDvsWD and WDvsWC combinations showed that there were 12differentially expressed genes in response to drought stress and brassinolide,three of them are genes involved in the regulation of antioxidant systems.Under drought stress,the expression of upstream genes BAK1 and BSK in brassinolide signaling pathway was down-regulated,which attenuated the signal transduction intensity of BR.The expression of BIN,a negative regulator downstream of BR pathway,was decreased under drought stress,which promoted the up-regulation of downstream transcription factor BZR1/BES1 gene and promoted BR synthesis.The expression of BIN in EBR treatment group was lower than that in non-treated group,indicate exogenous spraying of EBR can promote the synthesis of BR.Under drought stress,the dynamic pathway of synthesis and decomposition of ABA was unbalanced in the independent synthesis pathway of ABA.However,EBR treatment maintained endogenous ABA content by decreasing the degradation rate of ABA.In addition,in drought stress induces ABA biosynthesis related pathway,EBR enhanced the expression of ABA-synthetic transcription factor bHLHs,promote the continuous accumulation of ABA and enhance the drought resistance of plants.