Transcriptomics Analysis Of Paeonia Lactiflora In Response To Drought Stress And Functional Study Of Related Transcription Factors

Paeonia lactiflora Pall.is a famous flower in China.Its flowering period coincides with the late spring and early summer.In the northern part of China,there is a lot of drought-tolerant plants in the spring due to drought and little rain.However,in the landscaping,there is a widespread waste of water resources.Therefore,the research on the response of P.lactiflora to drought stress is of great significance to the breeding and application of P.lactiflora and the construction of water-saving gardens.In this study,different soil moisture levels were set,and ‘Karl Rosenfield' and ‘Da Fu Gui' were taken as the research objects.The physiological and biochemical indexes of the two cultivars under different drought treatments were measured,and ‘Karl Rosenfield' was used as the experimental material to perform transcriptome sequencing,gene cloning and mi RNA sequencing,and carried out preliminary research on its molecular mechanism in response to drought stress.The main findings are as follows:1.Under drought stress,a series of changes occurred in the phenotype and physiological and biochemical characteristics of P.lactiflora: The drought damage index(DDI)of ‘Karl Rosenfield' and ‘Da Fu Gui' leaves increased with the intensification of drought stress.Pn,Gs and Tr in the photosynthetic indicators showed a downward trend,while Ci did not change significantly.Among the chlorophyll fluorescence parameters,in addition to the NPQ showing an increasing trend,Fv/Fm,Y(II),q P,and relative chlorophyll content all showed a downward trend.The relative water content of the leaves decreased as the soil water decreased.The contents of malonaldehyde,soluble sugar,and proline in leaves and fibrous roots increased,but the changes in soluble protein contents were inconsistent.The activity of four antioxidant enzymes fluctuated.The content of ABA in soil showed an increasing trend with the decrease of soil moisture.The content of IAA and IAA/ABA changed irregularly,while the content of ZR and GA3 generally showed a trend of increasing first and then decreasing.2.Using the Illumina Hiseq platform to study the transcriptome of P.lactiflora leaves under drought stress,a total of 4198 differential genes were identified.GO function enrichment was performed on the differentially expressed genes.It was found that the catalytic activity entries were enriched in the three differentially expressed gene sets with the most differentially expressed genes.A total of eight KEGG enrichment pathways for each differentially expressed gene set were obtained,of which photosynthesis and plant hormone signal transduction pathways had more differentially expressed genes in the CK and SD sets.After screening,the related genes of P.lactiflora in response to drought stress were divided into four groups.Among them,there are 40 signal transduction and protein kinase genes,167 transcription factor genes,49 osmotic adjustment and antioxidase enzyme genes,and 68 photosynthesis and other functional protein genes.3.Seamless cloning technology was used to clone the two genes of peony Plb ZIP and Pl HD-Zip obtained by sequencing the transcriptome to obtain the c DNA sequence of the gene.Plb ZIP is 1290 bp in length and encodes 429 amino acids,and Pl HD-Zip is 972 bp in length and encodes 323 amino acids.The pcambia1301 expression vector was constructed for the two genes,and T3 generation lines were obtained after infecting Arabidopsis thaliana with the Agrobacterium-mediated flower dipping method.Identification and drought tolerance analysis of transgenic A.thaliana showed that the two genes,Plb ZIP and Pl HD-Zip,had certain enhancement effects on plant drought tolerance.4.The small RNAs of P.lactiflora leaves under drought stress were sequenced.A total of 58 known mi RNAs and 83 new mi RNAs were identified.Analysis of the identified mi RNA families revealed that they belonged to 38 mi RNA families,with the largest number of mi RNAs in the MIR396 family.19 mi RNAs were differentially expressed in the comparison between moderate and severe drought stress treatments and controls.Finally,based on the results of enrichment analysis,35 mi RNAs and 67 target genes that may be related to the drought stress of P.lactiflora were listed.