The MsDHN1-MsPIP2;1-MsmMYB module orchestrates the trade-off between growth and survival of alfalfa in response to drought stress

Dehydrins and aquaporins play crucial roles in plant growth and stress responses by acting as protector and controlling water transport across membranes, respectively. MsDHN1 (dehydrin) and MsPIP2;1 (aquaporin) were demonstrated to interact with a membrane-anchored MYB protein, MsmMYB (as mMYB) in plasma membrane under normal condition. MsDHN1, MsPIP2;1 and MsDHN1-MsPIP2;1 positively regulated alfalfa tolerance to water deficiency. Water deficiency caused phosphorylation of MsPIP2;1 at Ser 272, which led to release C terminus of mMYB (mMYB Delta 83) from plasma membrane and translocate to nucleus, where C terminus of MsDHN1 interacted with mMYB Delta 83, and promoted mMYB Delta 83 transcriptional activity in response to water deficiency. Overexpression of mMYB and mMYB Delta 83 down-regulated the expression of MsCESA3, but up-regulated MsCESA7 expression by directly binding to their promoters, and resulted in high drought tolerance in transgenic hairy roots. These results indicate that the MsDHN1-MsPIP2;1-MsMYB module serves as a key regulator in alfalfa against drought stress.

Automated summary

Dehydrins and aquaporins play crucial roles in plant growth and stress responses. The proteins MsDHN1 and MsPIP2;1 were found to interact with a membrane-anchored MYB protein, MsmMYB, under normal conditions. These proteins positively regulate alfalfa's tolerance to water deficiency. Water deficiency causes phosphorylation of MsPIP2;1, leading to the release of the C terminus of MsmMYB from the plasma membrane and its translocation to the nucleus. Once in the nucleus, the C terminus of MsDHN1 interacts with the C terminus of MsmMYB, promoting its transcriptional activity in response to water deficiency. Overexpression of MsmMYB and its C-terminal fragment down-regulates the expression of MsCESA3 but up-regulates the expression of MsCESA7, resulting in enhanced drought tolerance in transgenic hairy roots.