Drought stress limits the productivity of alfalfa which is one of the most important forage species around the world. WRKY transcription factors are critical TFs involved in drought stress response. In this study, an osmotic stress-responsive WRKY TF gene, named MsWRKY11, was cloned from alfalfa (Medicago sativa L.), which exhibits high expression level in stem and petiole. Its biological function and gene regulation mechanism were studied via overexpressed MsWRKY11 (MsWRKY11-OE) or dominantly repressed MsWRKY11 (MsWRKY11-SRDX) in alfalfa seedlings or hairy roots of alfalfa. The results showed that overexpression of MsWRKY11 in alfalfa decreased stomatal density in leaves and enhanced water use efficiency and drought tolerance. Lignin contents increased in the stem of MsWRKY11-OE plants under normal and drought conditions, but decreased in hairy roots of MsWRKY11-SRDX lines. MsWRKY22 was demonstrated to directly bind to W-box elements in MsWRKY11 promoter through in vitro and in vivo assays and positively activate MsWRKY11 expression. These results provide a new insight into the role of MsWRKY11 in regulating drought tolerance through lignin biosynthesis and stomatal formation in alfalfa.

干旱胁迫限制了苜蓿的生产力，苜蓿是世界上最重要的牧草之一。WRKY转录因子是参与干旱胁迫反应的关键TF。在这项研究中，从苜蓿（苜蓿（Medicago sativa L.））克隆了一个渗透胁迫应答性WRKY TF基因，命名为MsWRKY11，该基因在茎和叶柄中具有高表达水平。通过苜蓿幼苗或苜蓿毛根中过表达的MsWRKY11（MsWRKY11 -OE）或显性抑制的MsWRKY11（MsWRKY11 -SRDX）研究其生物学功能和基因调控机制。结果表明MsWRKY11过表达在苜蓿中减少叶片的气孔密度，提高水分利用效率和干旱耐受性。在正常和干旱条件下，MsWRKY11 -OE植物茎中木质素含量增加，但MsWRKY11 -SRDX系的有毛根中木质素含量下降。通过体外和体内试验，MsWRKY22可直接与MsWRKY11启动子中的W-box元件结合，并能积极激活MsWRKY11的表达。这些结果为MsWRKY11在苜蓿中通过木质素生物合成和气孔形成调节干旱耐受性的作用提供了新的见解。