Guo et al. demonstrate how perceived developmental signals modulate cytokinin homeostasis to shape the rice inflorescence. The Plant Cell (2020) https://doi.org/10.1105/tpc.20.00351.
By Tao Guo, Zi-Qi Lu, Jun-Xiang Shan, Wang-Wei Ye, Nai-Qian Dong, Hong-Xuan Lin
Background: Rice is one of the most important staple cereal crops worldwide, as it feeds more than half the world’s population. Rice yield is a complicated trait determined by tiller number, grain weight, and number of grains. Spikelet number per panicle is a flexible component that strongly contributes to grain yield. Rice has determinate inflorescences in which meristems differentiate into primary branch meristems attached to a central rachis, which then form several secondary branch meristems. However, we know very little about the intrinsic mechanisms by which spikelet number per panicle is ultimately determined in rice.
Question: We wanted to understand the molecular mechanisms that control the number of spikelets per panicle in rice. We also wanted to know how intrinsic signals perceived on the plant cell surface activate the reproductive meristem to determine organ number through nuclear signaling.
Findings: ERECTA1 (OsER1) is a negative regulator of spikelet number per panicle. Altering this gene directly influenced panicle patterning. We discovered that OsER1 acts upstream of the OsMKKK10-OsMKK4-OsMPK6 kinase cascade. Surprisingly, the OsER1-OsMKKK10-OsMKK4-OsMPK6 pathway is required for the maintenance of cytokinin homeostasis.
Next steps: We aim to improve crop yields to produce more grains per panicle. Our findings provide important insights into the developmental plasticity of the inflorescence and a potential means to cultivate high-yielding rice varieties. Perhaps crop scientists could genetically manipulate the OsER1 signaling pathway using new gene-editing technology to increase rice yields.
Tao Guo, Zi-Qi Lu, Jun-Xiang Shan, Wang-Wei Ye, Nai-Qian Dong, Hong-Xuan Lin (2020). ERECTA1 Acts Upstream of the OsMKKK10-OsMKK4-OsMPK6 Cascade to Control Spikelet Number by Regulating Cytokinin Metabolism in Rice. Plant Cell DOI: https://doi.org/10.1105/tpc.20.00351