| Buckwheat(Fagopyrum spp.)under the family Polygonaceae is a dicotyledon grain crop,which is widely cultivated in northwest China,North China,southwest China and Yun-gui Plateau.The seasonal water shortage occurs frequently in buckwheat planting area and seriously affected the growth and yield of buckwheat,due to the lack of watercontrolled measures and the backward irrigation technology.Therefore,the most costeffective means for ameliorate buckwheat production is breeding new drought resistant varieties base on the evaluation of drought resistant germplasm resources.In addition,mining novel drought tolerance genes and study and clarify the molecular mechanism of drought tolerance in common buckwheat can improve the exploiting and utilization of common buckwheat germplasm resources,and it has a great significance to cultivate drought resistant varieties of common buckwheat.In this study,transcriptomics and proteomics analysis were carried out to study the physiology and molecular mechanism of drought tolerance in buckwheat seedlings,and to explore the drought tolerance related genes.In addition,in order to explore the suitable stress concentration and index for the identification of the drought tolerance of common buckwheat and establish the buckwheat drought tolerance identification system at germination stage,and screening of droughttolerance common buckwheat germplasm resources,80 common buckwheat accessions from different regions were subjected for drought tolerance tests upon drought stress treatment.Main contributions of this work are as follows:(1)Under drought stress,common buckwheat seedlings exhibit certain physiological and morphological variations,shown by leaves wrinkled and the decreased of the relative water content.By contrast,drought stress increased the accumulation of the the MDA content,and enhanced the CAT and POD activities.And water deficit also significantly decreased the ratio of chlorophyll a/b and Rubis CO activities compared to the control treatment in 5 days of treatment.These results indicated that the activities of antioxidant enzymes of common buckwheat seedlings were improved to eliminate the redundant ROS.(2)The evident perturbations in the gene expression of light harvesting and Calvin cycle were discovered by transcriptome sequencing analysis,indicated that the photosynthetic capacity of common buckwheat seedlings was decreased under drought stress.There were different response patterns between aerial part and underground part of common buckwheat seedlings under drought stress.According to the GO and KEGG enrichment analysis,our results indicated that the different expressed genes(DEGs)which related to signal transduction,kinase activity,DNA modification and oxidoreductase activity were upregulated by the drought treatment in common buckwheat cotyledons,and the drought-induced DEGs were mainly involved in the macromolecule modification,protein modification process,protein phosphorylation,protein metabolic process,phosphorus metabolic process and carbohydrate metabolic process in common buckwheat roots.Meanwhile,the transcription factors(TFs)were greatly affected by drought stress,and also had different expression patterns between common buckwheat cotyledons and roots.(3)Proteomic analysis was carried out to investigate the change pattern of protein abundance level in common buckwheat cotyledons under 5 days drought stress treatment.Our analysis of the differentially abundance proteins(DAPs)showed that the significantly change terms were “phenylpropanoid biosynthesis”,“catalytic activity”,“styrene degradation” and “iron ion binding”.To further clarify the inter-connections among the DAPs,the PPI network analysis was performed and 14 DAPs were enriched in phenylalanine metabolic process and flavonoid biosynthesis pathways and 6 DAPs were enriched in DNA Replication and homologous recombination,and the abundant level of these DAPs were reduced under drought stress.Moreover,we found that the abundance level of 5 heat shock proteins and 1 TCP-1/cpn60 chaperonin family protein were highly induced by water deficit and these proteins were highly clustered and interacted with more drought-induced proteins.These proteins might respond to the drought stress condition and can be used as a candidate gene to improve drought tolerance of buckwheat.(4)In order to explore the drought resistance identification index of common buckwheat at germinating stage,and screen the drought-resistant common buckwheat germplasm materials,80 common buckwheat germplasm materials from different regions were subjected for drought resistance tests upon drought stress treatment by PEG6000 solution.Our results showed that 20% PEG6000 solution was optimal to screen the drought-resistant common buckwheat germplasm materials at germinating stage,and the significant correlations on drought tolerant coefficient were observed between sprout index of drought resisting,relative germination rate,relative root length index and root length stress index.These four indices were recommended for drought resistance evaluation in common buckwheat.The 80 common buckwheat germplasm materials were classified into four types,composing of 3 germplasm materials with high tolerance,13 with tolerance,33 with moderate tolerance and 31 with susceptibility.These results will provide theoretical guidance and basic information for future drought-resistant breeding in common buckwheat.(5)Allelic variation analysis of Fe DREB1 L gene and its promoter were carried out in 12 common buckwheat germplasm materials with different drought-resistant,and 4 kinds of Fe DREB1 L gene and 3 kinds of Fe DREB1 L promoter were isolated.Meanwhile,the promoter variations were mainly concentrated in the drought response regions,and different combinations of Fe DREB1 L gene and promoter were found in different droughttolerant germplasms.It is speculated that these variations may be related to the differentiation of drought tolerance of buckwheat germplasm resources. |
