干旱胁迫下偏关苜蓿保护酶及转录组差异性分析

Protective Enzyme and Transcriptome Difference Analysis of Medicago sativa ‘Pianguan’ in Response to Drought Stress

当前全球极端天气频发,干旱严重制约牧草的产量和品质。偏关苜蓿(Medicago sativa ‘Pianguan’)是山西地方品种,具有抗寒、抗旱性强以及营养价值高等特点。研究采用20%PEG对偏关苜蓿苗期进行干旱胁迫处理0(对照组)、72 h(干旱组),测定叶片SOD、POD、CAT和APX活性,利用高通量Illumina Hiseq测序技术对对照组和干旱组的叶片进行转录组测序。结果表明,偏关苜蓿干旱组的SOD、POD、CAT及APX的活性较对照组均显著上升;结果共得到79 794个Unigene,平均长度1 018 bp,对照组和干旱组差异表达基因中上调和下调表达数量分别是2 715、3 152个。差异表达基因的GO分析表明,对照组和干旱组的基因功能在代谢过程、催化活性、金属伴侣活性、抗氧化活性和酶调节活性差异显著;KEGG富集分析表明,差异表达基因在次生代谢物的生物合成、淀粉和蔗糖代谢以及植物激素信号转导等通路显著富集。研究获得干旱胁迫下偏关苜蓿对照组与干旱组差异表达基因的功能信息,发现bHLH35、ERF25、PCF7、RF2b等转录因子在偏关苜蓿响应干旱胁迫中具有重要作用,这些转录因子与苯丙氨酸酶、类胡萝卜素结合蛋白、光合作用蛋白、淀粉酶以及蔗糖合酶有关的基因可作为偏关苜蓿响应干旱胁迫的候选基因。

Currently, global extreme weather is frequent and as a kind of extreme weather, drought severely restricts yield and quality of forage. Medicago sativa ‘Pianguan’ is a local forage variety in Shanxi province with high resistance to cold and drought as well as high nutritional value. This study was conducted through simulating drought stress by 20% PEG. The Medicago sativa ‘Pianguan’ at seedling stage were treated with PEG for 0 h(control group)and 72 h(drought group)to meet the stress condition, leaf SOD, POD, CAT and APX activities were determined. Transcriptome sequencing was conducted on leaves of the control and the drought groups by high-throughput Illumina Hiseq sequencing technology. The results showed that the activities of SOD, POD, CAT and APX were significantly increased in the drought group of Medicago sativa ‘Pianguan’compared to the control group. 79 794 unigene with an average length of 1 018 bp were obtained by sequencing and analysis. The numbers of up-regulated and down-regulated expressions of differentially expressed genes between the control group and the drought group were 2 715 and 3 152. GO analysis of differentially expressed genes showed that the gene functions of the two groups were significantly different in metabolic process, catalytic activity, metal chaperone activity, antioxidant activity, and enzyme regulation activity. KEGG enrichment analysis found that differentially expressed genes were significantly enriched in pathways such as secondary metabolite biosynthesis, starch and sucrose metabolism, and plant hormone signal transduction.Information of function of differentially expressed genes of Medicago sativa ‘Pianguan’ in the control group and the drought group was gained in the study, finding that the transcription factors such as bHLH35, ERF25, PCF7, and RF2b played an important role in response to drought stress in Medicago sativa ‘Pianguan’. These factors and the genes related to phenylalanine enzyme,carotenoids binding protein, photosynthetic protein, amylase, and sucrose synthase could be candidate genes of Medicago sativa‘Pianguan’ in response to drought stress.