An Acyl-CoAN-Acyltransferase Regulates Meristem Phase Change and Plant Architecture in Barley1[OPEN]

The modification of shoot architecture and increased investment into reproductive structures is key for crop improvement and is achieved through coordinated changes in the development and determinacy of different shoot meristems. A fundamental question is how the development of different shoot meristems is genetically coordinated to optimize the balance between vegetative and reproductive organs. Here we identify theMANY NODED DWARF1(HvMND1) gene as a major regulator of plant architecture in barley (Hordeum vulgare). Themnd1.amutant displayed an extended vegetative program with increased phytomer, leaf, and tiller production but a reduction in the number and size of grains. The induction of vegetative structures continued even after the transition to reproductive growth, resulting in a marked increase in longevity. Using mapping by RNA sequencing, we found that theHvMND1gene encodes an acyl-CoAN-acyltransferase that is predominately expressed in developing axillary meristems and young inflorescences. Exploration of the expression network modulated byHvMND1revealed differential expression of the developmental microRNAsmiR156andmiR172and several key cell cycle and developmental genes. Our data suggest thatHvMND1plays a significant role in the coordinated regulation of reproductive phase transitions, thereby promoting reproductive growth and whole plant senescence in barley. MANY NODED DWARF1 encodes an acyl-CoA N-acyltransferase that acts as a major regulator of meristem phase change, promotes reproductive growth, and controls overall shoot architecture in barley.