Mitogen-activated protein kinase kinase kinases (MAPKKKs) are important components of the MAPK cascade and play crucial roles in development and stress responses. Arabidopsis pumila is an ephemeral Brassicaceae plant growing in Xinjiang desert regions, which possesses salt tolerance. To explore the evolution and function of the MAPKKK gene family in A. pumila, 143 ApMAPKKK genes were identified from A. pumila genome by genome-wide analysis, which were categorized into three subfamilies: ZIK (20), MEKK (36) and RAF (87). There existed 74 and 72 colinear genes between A. thaliana, A. lyrata and A. pumila, respectively, indicating that this gene family expanded obviously in A. pumila genome. Evolutionary analysis revealed that there were 64 duplicated gene pairs with Ka/Ks less than 1, and purifying selection was dominant. RNA-seq data were used to analyze the expression characteristics of ApMAPKKK genes in response to salt stress and in different tissues. The results showed that most ApMAPKKK genes were up-regulated under 250 mmol/L NaCl stress. For example, ApMAPKKK18-1/2 and ApMAPKKK17-1/2 were substantially up-regulated. Tissue expression profiles showed that ApMAPKKK mainly presented six expression patterns. Some duplicated genes were differentially expressed in response to salt stress and in different tissues. These results lay a foundation for further understanding the complex mechanism of MAPKKK gene family transduction pathway in response to abiotic stresses in A. pumila.
丝裂原活化蛋白激酶激酶激酶(Mitogen-activated protein kinase kinase kinases, MAPKKKs)是MAPK级联的重要组成部分，在发育过程和胁迫反应中发挥重要功能。小鼠耳芥(Arabidopsis pumila)是生活在新疆荒漠中的十字花科短命植物，具有很好的耐盐能力。为了探索小鼠耳芥MAPKKK基因家族的进化和功能，本研究通过全基因组分析从小鼠耳芥基因组中鉴定了143个ApMAPKKK基因，分属3个亚族：ZIK (20个)、MEKK (36个)和RAF (87个)。共线性分析表明小鼠耳芥与拟南芥和琴叶拟南芥分别存在74和72个共线性基因，说明该家族在小鼠耳芥基因组中发生了明显的扩张；进化分析表明存在64对复制基因对，Ka/Ks均小于1，以纯化选择为主。利用RNA-seq数据分析ApMAPKKK在盐胁迫和不同组织中的表达特征，结果表明在250 mmol/L NaCl胁迫下，大多数ApMAPKKK基因上调表达，其中ApMAPKKK18-1/2和ApMAPKKK17-1/2显著上调表达；而在8个组织中，ApMAPKKK主要呈现6种表达模式；部分复制基因在盐胁迫和组织中的表达模式存在差异。本研究结果为进一步解析小鼠耳芥MAPKKK基因家族成员响应非生物胁迫信号转导通路的复杂机制奠定了基础。.
Keywords: Arabidopsis pumila; MAPKKK; ephemeral plant; gene expression; salt stress.