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The loss-of-function GLABROUS 3 mutation in cucumber is due to LTR-retrotransposon insertion in a class IV HD-ZIP transcription factor gene CsGL3 that is epistatic over CsGL1

Yupeng Pan, Kailiang Bo, Zhihui Cheng, Yiqun Weng
BMC plant biology 2015 v.15 no.302 pp. -
DNA, aerial parts, amino acid sequences, chromosome mapping, cucumbers, epistasis, exons, gene expression, genetic background, loci, loss-of-function mutation, molecular cloning, mutants, phenotype, phylogeny, recessive genes, retrotransposons, sequence alignment, terminal repeat sequences, transcription factors, trichomes
Trichomes developed from the protodermal cells are hair-like structures covering the aerial parts of plants. Trichomes are of adaptive roles in evolution. The presence or absence of trichomes also constitutes an important quality issue for cucumber. In this study, we reported characterization and map-based cloning of a new trichome mutant, CUCUMBER GLABROUS 3 (csgl3), which exhibited completely glabrous phenotype on all aerial organs. Genetic analysis indicated that the glabrous phenotype was inherited as a single recessive gene, which was designated as csgl3. Fine genetic mapping delimited the csgl3 locus into a 68.4 kb genomic DNA region with 12 predicted genes. Evidence from genetic analysis, sequence alignment and allelic variations in natural populations suggested that the Arabidopsis PDF2-like gene was the only candidate gene for CsGL3, which was 5,188 bp in length with 10 predicted exons. Gene expression analysis revealed loss-of-function of CsGL3 in the mutant which was due to the insertion of a long terminal repeat retrotransposon in the fourth exon. Linkage analysis in segregation population and gene expression analysis of the CsGL1 and CsGL3 genes in csgl1, csgl3, and csgl1+3 genetic backgrounds revealed interactions between the two genes. Phylogenetic analysis among 28 class IV HD-ZIP protein sequences from five species placed cucumber CsGL3 into the same clad with seven other members that play important roles in trichome initiation. Findings from the present study provide new insights into genetic control of trichome development in cucumber.