Fine Mapping of CsVYL, Conferring Virescent Leaf Through the Regulation of Chloroplast Development in Cucumber

Abstract

Leaf color mutants in higher plants are ideal materials for investigating the structure and function of photosynthetic system. In this study, we identified a cucumber <i>vyl</i> (virescent-yellow leaf) mutant in the mutant library, which exhibited reduced pigment contents and delayed chloroplast development process. F₂ and BC₁ populations were constructed from the cross between <i>vyl</i> mutant and cucumber inbred line 'Hazerd' to identify that the <i>vyl</i> trait is controlled by a simply recessive gene designated as <i>CsVYL.</i> The <i>CsVYL</i> gene was mapped to a 3.8 cM interval on chromosome 4 using these 80 F₂ individuals and BSA (bulked segregation analysis) approach. Fine genetic map was conducted with 1542 F₂ plants and narrowed down the <i>vyl</i> locus to an 86.3 kb genomic region, which contains a total of 11 genes. Sequence alignment between the wild type (WT) and <i>vyl</i> only identified one single nucleotide mutation (C→T) in the first exon of gene <i>Csa4G637110</i>, which encodes a DnaJ-like zinc finger protein. Gene Expression analysis confirmed the differences in transcription level of <i>Csa4G637110</i> between wild type and mutant plants. Map-based cloning of the <i>CsVYL</i> gene could accelerate the study of chloroplast development and chlorophyll synthesis of cucumber.