| Drought is an important factor which restricts the growth of common bean.It has important significance to explore the response of common bean to drought stress at seedling stage for the efficient production of common bean and the breeding of stress-resistant varieties.In this study,Longyundou 10 and Longyundou 17 were selected as experimental materials to study the drought stress response and transcriptome analysis of seedling common beans.The effects of drought stress on growth,physiology and biochemistry of seedling common beans were clarified,and the physiological indexes of drought resistance identification and drought resistance breeding objectives of common beans were determined.Using transcriptome sequencing technology,the response of common bean to water stress was studied at the molecular level in order to provide data and methods for stress resistance gene mining and molecular assisted breeding in the future.The main results were as follows:1.The results showed : with the prolongation of drought stress time and the increase of drought stress degree,the growth and root development of common bean seedling were inhibited,and the effect of drought stress on Longyundou 10 was greater than Longzhidou17.Under severe drought stress,the total root length,root surface area and root volume of Longyundou 10 decreased by 24.5%,42.9% and 33.5%,respectively.The root development indexes of Longyundou 17 decreased by 23.2%,34.2% and 29.5%,respectively.2.Light drought stress can increase ABA level in leaves of common bean in seedling stage,and the response mechanism of IAA and CTK to drought stress is relatively complex.ABA in drought-tolerant cultivar responded more positively to drought stress,and ABA could be used as an important index for drought resistance identification of of common bean in seedling stage.3.Under drought stress,the contents of proline and betaine in the leaves of common bean seedlings increased,and the maximum increase of proline content was more than 1.6 times than that under non-stress.In the early stage of drought stress,the soluble sugar of common bean increased significantly.The content of soluble sugar and proline could be used as an important physiological index for breeding common bean varieties with high drought resistance.Under drought stress,the main pathway of proline synthesis in common bean seedling leaves is glutamic acid pathway involving P5 CS.P5CS/Pro DH interaction was stronger than OAT/Pro DH in coping with drought stress.4.Longyundou 17 was stronger than Longyundou 10 in inhibiting the production of reactive oxygen species.Malondialdehyde content under drought stress was SS > LS > CK,and malondialdehyde could be used as a physiological index for identification of drought resistance of common bean at seedling stage.Drought stress can increase the activities of APX,GPX,SOD,CAT and POD in the antioxidant system of common bean seedling leaves,which indicates that the antioxidant system plays a positive role in protecting common bean seedling from peroxidation damage in response to drought stress.5.From the distribution of phosphorus,potassium,calcium,magnesium and zinc in common beans at seedling stage,the content increased from bottom to top.Drought stress inhibited the accumulation of phosphorus,potassium and calcium in roots and decreased the accumulation of potassium and calcium in stems.The results showed that potassium,calcium and zinc in leaves could be used as important indicators for drought resistance identification of common bean at seedling stage.6.A total of 27302 genes were detected by transcriptome sequencing.The number of differentially expressed genes in Longyundou 17 induced by waterlogging and drought stress was 717 and 1584,respectively,and 4400 and 235 in Longyundou 10.According to the results of differential gene detection,the GO function was classified and enriched.The results showed that water stress had significant effects on carbohydrate metabolism,hydrolase activity,polysaccharide metabolism and redox enzyme activity of Longyundou 17,and on photosynthetic system and ribosome biosynthesis and metabolism of Longyundou 10.The results showed that drought stress caused the changes of starch and sucrose metabolism,MAPK signal transduction pathway and other related genes in Longyundou 17.In Longyundou 10,drought stress caused significant changes on expression level in terpenoid biosynthesis,linoleic acid metabolism and other genes.The transcription factor family of differentially expressed genes was classified and the expression of transcription factors was clustered.A total of 2157 transcription factor coding genes were predicted,which belonged to 60 transcription factor families.It was concluded that AP2-EREBP,WRKY and NAC transcription factors play important roles in water stress response of two common bean varieties.According to the results of GO and Patway functional analysis,38 drought-resistant genes,such as 18630745,were inferred through comprehensive analysis of differential gene expression,differential expression multiple and reference genome comparison.These genes were closely related to the drought stress response mechanism of common bean,including antioxidant system,endogenous hormones,osmotic regulation system and mineral ion elements. |
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