Gene mapping and functional characterization of the maize albino mutant ZmCMK1

Photosynthesis underpins plant growth. Leaf-color mutants, displaying aberrant chloroplast development and pigment metabolism, are valuable for elucidating photosynthetic mechanisms. We characterized a natural albino mutant, abl1, from maize inbred line KN5585. Multi-environmental phenotyping confirmed its albino leaves and seedling lethality at the three-leaf stage, accompanied by significantly reduced chlorophyll and carotenoid contents. Genetic analysis indicated monogenic recessive inheritance. BSR-seq initially mapped abl1 to a 65-Mb region on chromosome 3. Fine-mapping delineated a 531-kb critical interval harboring 13 candidate genes. Integrated transcriptome and qRT-PCR analyses revealed that Zm00001d043182, encoding a key enzyme in the methylerythritol phosphate (MEP) pathway, was markedly downregulated. The mutant was thus renamed CMK1. Allelism tests with an independent EMS-CMK1 allele (crossing heterozygotes) yielded a 3:1 segregation of albino progeny, confirming Zm00001d043182 as the causal gene. The study identifies Zm00001d043182 as the gene responsible for the abl1 albino phenotype, offering new insights into the molecular basis of leaf color variation in maize.