Narrow Leaf 1 (NL1) encodes a CELL DIVISION CYCLE 48-like protein that controls leaf width in bread wheat

Leaf width is an important component of plant architecture that strongly affects light capture during photosynthesis and thus grain yield, particularly under dense planting conditions. However, the genetic and molecular mechanisms regulating leaf width in wheat (Triticum aestivum L.) remain unclear. Here, we identified the narrow-leaf mutant nl1 with fewer small veins than the wild-type and isolated the narrow-leaf gene Narrow Leaf 1 (NL1) through a combination of map-based cloning and bulked segregant exome capture sequencing (BSE-seq). NL1 encodes CELL DIVISION CYCLE 48-like (CDC48-like). A single Ser-to-Phe amino acid substitution in this protein led to a narrow-leaf phenotype. Transcriptomic analysis and measurement of endogenous phytohormone levels in nl1 vs. the wild-type suggested that NL1 might regulate cell division and the cytokinin pathway to control leaf width. Haplotype analysis showed that Hap2 of NL1 has been selected during wheat breeding. These findings provide insights into the genetic and molecular mechanisms underlying the role of NL1 in regulating leaf width and point to the potential of Hap2 for improving wheat plant architecture.