Abstract: The MYB (v-myb avian myeloblastosis viral oncogene homolog) family is one of the largest transcription factor families. The R2R3-MYB subfamily is widely involved in the stress response,secondary metabolism,growth and development of plant. In this study,R2R3-MYB transcription factors were identified in alfalfa. Their sequence characteristics,phylogenetic relationship,chromosome distributions,gene structures,cis-elements,and expression patterns under drought stress were analyzed by bioinformatic methods. The results showed that there were 121 members of the R2R3-MYB subfamily in Alfalfa. Each member had two typical MYB binding domains,the physical and chemical properties of which were yet different. These 121 members were divided into 33 groups by phylogenetic analysis,and each member was located irregularly on one of the 8 chromosomes. The analyses of gene structures and cis-elements showed that there were the same or similar numbers of exon and cis-elements within the same group. The expression levels of MsMYB12,MsMYB45,MsMYB52,MsMYB73,MsMYB88,MsMYB124,MsMYB149,MsMYB189,MsMYB268genes were significantly up-regulated in response to drought stress. It provides potential targets for studying the mechanism of R2R3-MYB transcription factor genes in response to drought stress in alfalfa.

Key words: Alfalfa, R2R3-MYB, Bioinformatic analysis, Drought stress, Expression patterns

摘要： MYB(v-myb avian myeloblastosis viral oncogene homolog)家族是最大的转录因子家族之一，R2R3-MYB亚家族在植物胁迫响应、次级代谢、生长和发育等过程发挥重要作用。本研究利用紫花苜蓿(Medicago sativa 'Zhongmu No.1’)基因组和转录组数据，通过生物信息学方法鉴定了R2R3-MYB转录因子，并对其序列特征、系统进化、染色体分布、基因结构、顺式作用元件及干旱胁迫下的表达模式进行分析。结果显示，紫花苜蓿中有121个R2R3-MYB亚家族成员，各成员均具有两个典型的MYB结构域，理化性质变化较大。系统进化分析将121个成员分为33个组，各成员无规律地定位在8条染色体上。基因结构和顺式作用元件分析发现，同一分组具有相同或相似的外显子数和顺式作用元件。响应干旱胁迫表达模式分析和实时荧光定量PCR(qRT-PCR)结果表明干旱胁迫下MsMYB12，MsMYB45，MsMYB52，MsMYB73，MsMYB88，MsMYB124，MsMYB149，MsMYB189，MsMYB268基因的表达量显著上调，可作为后期紫花苜蓿响应干旱胁迫机制研究的潜在靶点。

关键词: 紫花苜蓿, R2R3-MYB, 生物信息学分析, 干旱胁迫, 表达模式