| Aegilops tauschii (2n=2x=14, DD) is the donor of D genome of common wheat, this species alwaysgrows in extremely harsh environments, such as at the margins of deserts, in wastelands, on stony hills, andthey have a strong natural resistance. After the study on the identification of drought resistance of Aegilopstauschii in Xinjiang and Henan region, we find the XJ002which have highest drought resistance and theXJ098which have lowest drought resistance. Their seedlings are dealed with drought stress by20%PEG(polyethylene glycol), and total RNA was extracted from leaves with the control group (normal growth) fortranscriptome sequencing analysis. System for elucidating the pathway may be involved the Aegilopstauschii under drought stress, and analysis of the differentially expressed genes after drought stress.Through analysis of the regulation of genes expression between XJ002and XJ098, find out the keycandidate gene may be involved in drought stress regulatory network. The purpose of this study is to revealthe mechanism of drought tolerance of Aegilops tauschii, and provides gene resources of wheat breedingfor drought resistance.The research mainly includes the following aspects.1. It was completed that the bud period of drought simulation test of155Aegilops tauschii collectedfrom Xinjiang and Henan regions by the coleoptile length index20%PEG-6000(polyethylene glycol)hypertonic solution, mass for screening drought resistant phenotype of Aegilops tauschii accessions. Sixcopies of materials from two areas whose coleoptile processing length is longest, medium and the shortestwere tested by two times of drought rehydration of statistical drought survival rate, and XJ002droughtresistance was the highest with XJ098was the lowest, at the same time, drought survival rate of XJ002is ashigh as92.5%while the drought survival rate of XJ098only is56.5%.2. In order to compare the difference of drought resistance of XJ002and XJ098from the phenotypeand physiological and biochemical indexes, the root length of XJ002and XJ098which in normal growthcondition were determinated, the physiological and biochemical indexes in different time under the stressof PEG, including ABA (abscisic acid), Pro (proline), WSS (soluble sugar content), MDA(malondialdehyde), POD (peroxidase), PPO (polyphenol oxidase) and leaf osmotic medium relativeelectrical conductivity were measured. The accumulation of ABA synthesis is different obviously, and all the indexes reflecting the drought resistance of XJ002was stronger than that of XJ098.3. In order to find out the reasons of the difference of ABA content, NCED1gene sequences wereobtained respectively from XJ002and XJ098by the method of homology gene cloning, NCED is a keyenzyme in ABA synthesis pathway. The CDS sequence of Aegilops tauschii NCED1gene is1848bp,encoding615amino acid, without intron, with NCED protein typical domain. But the gene sequences ofXJ002and XJ098are identical, indicating the drought resistance difference may not directly controlled bythe difference of sequence for NCED1gene. The RT-PCR results between XJ002and XJ098, which underdifferent time point of PEG stress, showed that the expression level of NCED1gene gradually increasesfirstly and then decreases, indicating that the NCED1gene expression in response to drought stress.4. The seedlings of XJ002and XJ098wree treated by20%PEG through8hours (The leaves of XJ098began to wilt and no significant change in XJ002), at the same time, four groups of samples were collectedfrom the treated and normal growth condition from XJ002and XJ098, repeat three biological group, totalRNA was extracted from leaf tissue and for transcriptome sequencing analysis. The sequencing wereobtained from59.74G data and295.79M reads, the Q30(base error rate is1‰) reached80%, thealignment efficiency among sample reads and the reference genome is more than70%,3854new geneswere discovered, and optimization of the genomic structure, the statistics of SNP sites, find out six variableshear modes which exon skipping is the dominant in Aegilops tauschii. Analysis of gene expressiondifferences between different groups by fold change method,107key candidate genes may be involved indrought stress response are identified, all the differentially expressed gene were completed for patternclustering, functional annotation and enrichment. Transcriptome sequencing results showed, the expressionof NCED1induced by high level expression after drought stress, but XI002and XJ098NCED1expressionwas not significantly different. In addition, the results showed that ZEP (zeaxanthin epoxidase) geneexpression is slightly reduced and AAO (abscisic aldehyde oxidase) gene expression was slightly higher inthe pathway of ABA synthesis after drought stress, but their expression levels in XI002and XJ098had nosignificant differences after drought stress. |
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