Physiological And Transcriptomic Responses Of Fragaria Nilgerrensis Under Drought Stress

Fragaria nilgerrensis is an mnportant wild strawberry in Southwest China.It has excellent fruit qualities and strong resistance,especially drought resistance.It is an important resource for improving strawberry quality.In this study,physiological indexes and transcriptomes of F.nilgerrensis under drought stress were tested to reveal the mechanism of drought resistance quality of F.nilgerrensis.Understanding the molecular mechanism of Fnilgerrensis in response to drought stress is of great significance for the selection of drought-resistant strawberries.In this study,the dynamic changes of physiological indexes such as antioxidant enzyme activity and osmotic adjustment substance content in different time of drought stress were studied.At the same tine,the transcriptome sequencing of F.nilgerrensis leaves was carried out at different time points of drought stress.Differentially expressed genes were characterized by functional annotation and pathway enrichment.The main findings are as follows:The F.nilgerrensis of laboratory was treated with drought(the control group watered every 2 days,and the whole process of drought treatment was not water).The dynamic changes of antioxidant enzyme activity and osmotic adjustment substance content of day 0(TO),day 4(T4),day 8(T8),and day 12(T12)of strawberry leaves were determined.The results showed that with the increase of drought stress,the content of malbndiaklehyde(MDA)in the leaves of F.nilgerrensis increased significantly.With the degree of stress increased,relative conductivity showed an increasing trend.Similarly,intracellular osmotic substances increased,proline content increased too,and antioxidant enzymes(SOD,POD)activity increased significantly.In summary,F.nilgerrensis can quickly remove active oxygen and osmotic regulation under drought stress,reducing the damage of plants caused by drought.In order to study the molecular mechanism of F.nilgerrensis adapting to drought stress,the molecular mechanism of the transcriptional level of F.nilgerrensis leaves under drought stress was studied by RNA-seq.In this study,F.nilgerrensis leaves at Od,4d,8d and 12d under drought treatment were sequnced.Three biological replicates were pERFormed for each sample,and Od was viewed as control.There were more than 37,404,696 reads per sample,and each sample was tested to a depth of 10M,and 94%of the samples were aligned to the reference genome,indicating good sequencing quality.During the drought stress,the total number of genes down-regulated by the F.nilgerrensis was higher than the up-regulated gene(5728vs4595).There were 401 genes which were differentially expressed in T4,T8 and T12.Among them,131 genes were up-regulated in three drought treatment periods,and 269 genes were down-regulated.From the perspective of GO and KEGG enrichment,the overall metabolism of F.nilgerrensis under drought stress showed growth,photosynthesis:inhibited,and amino acid synthesis,protein translation promoted.The genes with up-regulated were related to response drought stress of F.nilgerrensis,including osmotic adjustment,stress protein plant hormones and transcription factors.The regulation of plant response to drought stress mainly includes ABA-dependent pathway and ABA-independent pathway.In our study,we found that NCED is significantly up-regulated under drought stress.This gene is a key enzyme for the synthesis of ABA.At the same time,bZIP and WRKY transcription factors are continuously up-regulated,further promoting downstream fimctional proteins such as LEA(enriched protein in late embryonic development).Expression of genes closely related to drought response,such as ERF(ethylene-responsive transcription factor),GolS(inositol galactose synthase),HSF(heat shock protein),UGT(UDP glycosyltransferase).Therefore,we speculate that the drought response regulation of F.nilgerrensis is dominated by ABA-dependent pathway.In addition,the stress factors including MYB,bHLH,NAC,WRKY,AP2/EREBP,bZIP,HSF and other transcription factor family genes were induced by drought stress,indicating that upstream regulatory elements were involved in drought stress response.