GmWOX1 regulates the mediolateral polarity of compound leaves in soybean

The morphology of soybean ( Glycine max ) leaves is a key agricultural trait that determines the planting density and photosynthetic efficiency. In soybean-producing regions of Northern China, narrow-leaf varieties carrying loss-of-function mutations in the ​ Ln ​gene are widely cultivated and have been incorporated into breeding programs, as the narrow-leaf trait enhances light-use efficiency under high-density planting conditions. However, the molecular mechanism underlying mediolateral axis development of soybean leaf is largely unknown. The WUSCHEL-RELATED HOMEOBOX transcription factor WOX1 plays a key role in mediolateral leaf development. Here, we identified four WOX1 homologs in soybean and determined that GmWOX1a and GmWOX1b are specifically and highly expressed in the middle domain of the leaf primordium. Heterologous expression of GmWOX1a fully complemented the leaf defects of the Nicotiana sylvestris lam1 mutant. Gmwox1acd and Gmwox1bcd triple mutant produced by gene editing exhibited narrow leaves and developmental abnormalities. However, Gmwox1a, Gmwox1b, and Gmwox1cd displayed no visibly altered phenotypes, suggesting functional redundancy among the WOX1 homologs. These findings demonstrate that the four WOX1 homologs redundantly regulate mediolateral axis development in soybean leaves, providing a basis for future studies on leaf morphology and soybean breeding.