A Mutation in Encoding a Plastid Isoform of Triose Phosphate Isomerase Leads to () in Cucumber ( L.).

The leaf is an important photosynthetic organ and plays an essential role in the growth and development of plants. Leaf color mutants are ideal materials for studying chlorophyll metabolism, chloroplast development, and photosynthesis. In this study, we identified an EMS-induced mutant, , which exhibited yellow cotyledons and true leaves that did not turn green with leaf growth. The locus was controlled by a recessive nuclear gene. The was mapped to a 166.7-kb genomic region on chromosome 2, which contains 24 predicted genes. Only one non-synonymous single nucleotide polymorphism (SNP) was found between and wt-WD1 that was located in Exon 7 of , resulting in an amino acid substitution. encodes a plastid isoform of triose phosphate isomerase (pdTPI), which catalyzes the reversible conversion of dihydroxyacetone phosphate (DHAP) to glyceraldehyde-3-phosphate (GAP) in chloroplasts. was highly expressed in the cotyledons and leaves. The mesophyll cells of the leaves contained reduced chlorophyll and abnormal chloroplasts. Correspondingly, the photosynthetic efficiency of the leaves was impaired. Identification of is helpful in elucidating the function of ptTPI in the chlorophyll metabolism and chloroplast development and understanding the molecular mechanism of this leaf color variant in cucumber.