title: Map-based cloning, identification and characterization of the w gene controlling white immature fruit color in cucumber (Cucumis sativus L.).
abstract: A single-nucleotide insertion resulted in a premature stop codon that is responsible for white immature fruit color in cucumber. Despite our previous progress in the mapping of the gene controlling white color in immature cucumber fruit and the identification of candidate genes, the specific gene that governs chlorophyll metabolism and its regulatory mechanism remains unknown. Here, we generated a mapping population consisting of 9497 F2 plants to delimit the controlling gene to an 8.2-kb physical interval that defines a sole candidate gene, APRR2. Sequencing the full-length DNA and cDNA of APRR2 allowed for identification of an allele, aprr2, encoding a truncated 101-amino acid protein due to a frameshift mutation and a premature stop codon. Gene structure prediction indicated that these 101 residues are located in a domain necessary for the function of the protein. The expression patterns of APRR2 were entirely consistent with the visual changes in green color intensity during fruit development. A microscopic observation of the fruit pericarp revealed fewer chloroplasts and a lower chloroplast chlorophyll storage capacity in Q24 (white) than in Q30 (green). A single-base insertion in the white color gene w, which leads to a premature stop codon, is hypothesized to have disabled the function of this gene in chlorophyll accumulation and chloroplast development. These findings contribute to basic research and the genetic improvement of fruit color.
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Hanqiang
authors.initials: H
authors.lastname: Liu
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Jianqing
authors.initials: J
authors.lastname: Jiao
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Xinjing
authors.initials: X
authors.lastname: Liang
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Huanwen
authors.initials: H
authors.lastname: Meng
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Shuxia
authors.initials: S
authors.lastname: Chen
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China. chengzh@nwsuaf.edu.cn.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Cheng
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D002734:Chlorophyll / Q000737:chemistry*; D002736:Chloroplasts / Q000737:chemistry; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018389:Codon, Nonsense / Q000235:genetics; D018553:Cucumis sativus / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D016368:Frameshift Mutation; D005638:Fruit / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D018389:Codon, Nonsense; D018744:DNA, Plant; D010940:Plant Proteins; D002734:Chlorophyll