大豆叶片响应CO_(2)浓度升高、干旱及其交互作用的转录组分析

Transcriptome analysis of leaves responses to elevated CO_(2) concentration,drought and interaction conditions in soybean[Glycine max(Linn.)Merr.]

气候变暖及大气CO_(2)浓度升高成为全球共识,由此增加极端天气气候事件(干旱)发生的频率和强度并对大豆生产带来不确定性。本研究通过大豆表型和叶片转录组测序(RNA-seq)分析,阐释CO_(2)浓度升高、干旱及其交互条件对大豆基因表达影响,明确CO_(2)浓度升高影响大豆耐旱性的调控途径,并在两个不同遗传背景品种中验证,从分子水平为未来气候变化背景下大豆抗旱育种提供理论参考。表型结果表明,CO_(2)浓度升高促进了大豆的生长并缓解干旱胁迫的负面效应。叶片转录组测序分析共筛选到89个CO_(2)响应基因,KEGG分类显示这些基因主要参与抗氧化物质(萜类、黄酮类等)代谢,同时特异性差异表达基因功能主要集中在细胞组分和生长发育方面。干旱条件下筛选的1006个差异表达(16倍)基因主要参与各类氨基酸(脯氨酸、色氨酸等)代谢途径,绝大多数蛋白质合成与转运相关基因上调,表明干旱胁迫下大豆叶片内物质合成交换过程加强。交互条件下筛选出的8566个差异表达基因主要参与碳水化合物代谢,光合作用-天线蛋白途径的相关基因几乎全部下调表达,表明交互条件下大豆光合能力下降。34个基因在3种条件下均差异表达,这些基因主要集中在抗氧化物质(黄酮类物质、谷胱甘肽、苯丙素等)代谢方面,且多数参与各类植物激素代谢和刺激响应。6个具有抗旱性功能的差异表达基因在两个不同遗传背景品种中的qRT-PCR结果说明RNA-seq数据准确。总之,CO_(2)浓度升高提高了大豆叶片抗氧化物质代谢和生长发育相关基因的表达;干旱胁迫诱导各类氨基酸代谢和蛋白质合成途径相关基因表达;交互条件下大豆光合能力受限,CO_(2)浓度升高主要通过调控激素代谢、抗氧化物质(抗氧化酶类、黄酮类、苯丙素等)代谢、碳水化合物代谢等途径提高大豆对干旱胁迫的耐受性。

Global consensus on climate warming and elevated atmospheric CO_(2) concentrations has increased the frequency and intensity of extreme weather events(droughts)and brought uncertainty about soybean production.In this study,the effects of elevated CO_(2) concentration,drought and their interaction on gene expression in soybean were elucidated by phenotypic and leaf transcriptome sequencing(RNA-seq)analysis.To provide theoretical reference for soybean breeding under the background of future climate change,we identified the regulatory pathway of CO_(2) affecting soybean drought tolerance.The phenotypic results showed that elevated CO_(2) concentration promoted the growth and alleviated the negative effects of drought stress on soybean.The results revealed that a total of 89 CO_(2)-responsive genes were identified by transcriptome sequencing analysis.KEGG classification demonstrated that these genes were mainly involved in antioxidant metabolism(terpenoid,flavonoid,etc.),meanwhile,Functional of the specific differentially expressed gene mainly focused on cell components,growth,and development.Under drought condition,1006 highly differentially expressed(16-fold)genes were screened out.These genes were mainly involved in various amino acid(proline,tryptophan,etc.)metabolic pathways,and almost all genes involved in protein synthesis and transport were up-regulated,indicating that there were a lot of material exchange processes in soybean leaves under drought stress.A total of 8566 differentially expressed genes,mainly involved in carbohydrate metabolism pathway,were detected under the interaction,and almost all genes related to the photosynthesis-antenna protein pathway were down-regulated,suggesting that the photosynthetic capacity of soybean was decreased under the interaction.34 genes were found to be differentially expressed under all three conditions.These genes were mainly concentrated in antioxidant metabolism(flavonoids,glutathione,phenylpropanoids,etc.),and most of these genes were involved in the metabolism of various plant hormones and stimulus responses.The qRT-PCR results of six differentially expressed genes related to drought resistance in two soybean varieties with different genetic background showed that the RNA-seq data were accurate.In conclusion,elevated CO_(2) concentration could increase the relative expression levels of genes related to antioxidant metabolism,growth and development in soybean leaves.Drought stress induced the relative expression levels of genes related to amino acid metabolism and protein synthesis pathway.The photosynthetic capacity of soybean was inhibited under the interactive condition.Elevated CO_(2) concentration enhanced the tolerance of soybean to drought stress by regulating hormone metabolism,antioxidant(antioxidant enzyme,flavonoid,phenylpropanoid)metabolism and carbohydrate metabolism.