Recessive antimorph alleles reveal novel functions of the OPAQUE1 myosin XI in maize

Ideal plant architecture optimizes canopy structure and increases grain yield in maize. However, its underlying genetic mechanisms remain poorly characterized. Two recessive, EMS-induced maize mutants were identified that have reduced stature, opaque kernels, and abnormal subsidiary cell division, and are allelic toopaque1 (o1). These two new missense alleles,o1-2995ando1-tan62, unlike the loss-of-function alleles previously identified, generate O1 protein but paradoxically generate more severe morphological defects. These defects include reduced internode elongation and partial suppression of excessive tassel and ear branching inramosa1 (ra1), ra2, and ra3mutants. We show thato1-2995ando1-tan62are novel alleles ofo1, and play a role in plant growth via internode elongation, subsidiary cell division positioning, leaf patterning, inflorescence development, and overall plant architecture.