Molecular Regulation of Maize Plant Height and Its Implications for Breeding Maize Tolerant to Enhanced Planting Density

The continuous increase in maize yield has become increasingly dependent on high-density planting, rendering plant height (PH) and plant architecture core traits that balance light interception efficiency and lodging resistance. Although many PH regulators have been well characterized, we are still confused on how to handle these regulators for maize breeding. At the same time, biotechnological advances have provided us with tools to address this issue. This review presents perspectives on integrating molecular information underlying maize PH regulation with these biotechnological tools to improve high-density tolerance in maize. We first compile an inventory of genes associated with maize PH and classify them into hormone-related and non-hormonal pathways, and reveal that loss-of-function mutations in most of these genes exhibit prominent allelic characteristics, including extreme dwarfism and pleiotropy. We discuss the underlying mechanisms of pleiotropy, which is important for successful editing aimed at achieving moderate dwarfism. Then, we discuss current strategies for high-density tolerance improvement, including genome editing strategies, introgression of dominance genes, multi-gene stacking, and phenotypic prediction, and offer key insights for their practical implementation. We offer insights and perspectives for future high-density tolerance improvement, which requires cell-resolution gene regulatory networks, AI-enabled precision genome editing, and phenotypic prediction models incorporating all environmental factors influencing plant growth. This review aims to provide guidance for researchers and breeders in translating molecular knowledge into improved high-density tolerance, lodging resistance, and yield gain.