A kelch-repeat superfamily gene, ZmNL4, controls leaf width in maize (Zea mays L.).

Leaf width (LW) is an important component of plant architecture that extensively affects light capture during photosynthesis and grain yield particularly under dense planting conditions. However, the genetic and molecular mechanisms regulating LW remain largely elusive in maize (Zea mays L.). In this study, qLW4a, one major quantitative trait locus controlling LW, was identified in the population constructed by maize inbred lines PH6WC with wide leaf and Lin387 with narrow leaf. Map-based cloning revealed that ZmNL4, a kelch-repeat superfamily gene, emerged to be the candidate for qLW4a, and a single-base deletion in the conserved SMC_prok_B domain of ZmNL4 in Lin387 caused a frame shift leading to a prematurely termination. Consistently, knockout of ZmNL4 by CRISPR/Cas9 editing significantly reduced LW, which was attributed to a reduction in the cell number instead of cell size, indicating a role of ZmNL4 in regulating cell division. Transcriptomic comparison between ZmNL4 knockout lines and the wild type B73-329 revealed that ZmNL4 might participate in cell wall biogenesis, asymmetric cell division, metabolic process, transmembrane transport and response to external stimulus, etc. These results provided insights into the genetic and molecular mechanisms of ZmNL4 in controlling LW and potentially contributed to optimize plant architecture for maize breeding.