The maize ZmCPK39-ZmKnox2 module regulates plant height

Plant height is an important agronomic trait that affects high-density tolerance and lodging resistance.However,the regulators and their underlying molecular mechanisms controlling plant height in maize remain understudied.Here,we report that knockout mutants of the calcium-dependent protein kinase gene ZmCPK39(ZmCPK39-KO)exhibit dramatically reduced plant height,characterized by shorter internodes and a slight decrease in node numbers.Furthermore,we identified a ZmCPK39-interacting protein,the knotted-related homeobox(ZmKnox2),and observed that plant height was also significantly reduced in a mutator transposon-inserted mutant of ZmKnox2(ZmKnox2-Mu).Combined analysis of transcriptomic and metabonomic data indicates that multiple phytohormone signaling and photosynthesis pathways are disrupted in both ZmCPK39-KO and ZmKnox2-Mu mutants.Taken together,these results provide new insights into the function of ZmCPK39 and identify potential targets for breeding lodging-resistant and high-density tolerant maize cultivars.