Mapping And Cloning Of Related Gene For Fruit Spines Formation In Cucumber

The wild-type cucumber has trichomes on foliage and spines on fruit. The leaf trichomes and fruit spines have similar shape and structure with histology analysis in cucumber, and both structures are multicellular, non-glandular trichomes. Cucumber fruit is most important part of economic character, and breeding objectives for improvement are often focused on fruit yield and quality. The fruit spine is important trait of fruit appearance quality.Simple sequence repeat markers derived from expressed sequence tags (EST-SSR) are potentially valuable tools for plant breeding and germplasm collection conservation, and increasingly, efforts have been made for developing this type of marker. In this study, we have identified 9 polymorphic SSR markers from cucumber fruit EST deposited in public sequence database. The average allele number was 2.1 per locus, ranging from two to three alleles during screening 7 cucumber genotypes. Genetic similarity coefficient ranged from 0.22-1, with an average of 0.66 among 7 cucumber genotypes. Amplification products were also detected by 27 pairs of primer in 3 melon genotypes. These informative EST-SSR markers can be used in cucumber genome research.A bacterial artificial chromosome (BAC) library consisting of 19,200 clones with an average insert size of 105 kb has been constructed from a cucumber (Cucumis sativus L.) inbred line S94, derived from a cultivar in North China. The entire library was equivalent to approximately 5 haploid cucumber genomes. To facilitate chromosome engineering and anchor the cucumber genetic linkage map to its chromosomes, 15 sequence-characterized amplified regions (SCAR) and seven simple sequence repeats (SSR) markers from each linkage group of cucumber were used to screen an ordered array of pooled BAC DNA with polymerase chain reaction (PCR). Fifteen markers gave at least two positive clones. As a result, twenty-two BAC clones representing 7 linkage groups of cucumber were identified, which further validated the genome coverage and utility of the library. This BAC library and linkage group specific clones provide essential resources for future research of the cucumber genome.To mapping gene of fruit spine formation, we was constructed segregate populations with inbred line S06 (Europe greenhouse type) and glabrous (gl) mutant. The trichoms characteristic of foliage surface was controlled by a pair of nuclear genes. The characteristic of trichomes (Gl) was dominant to that of glabrous foliage (gl) with heredity analysis. The gene of foliage trichomes also controlled fruit spines. The Gl gene together with Tu gene decided fruit surface, which showed three phenotypes on fruit: have warts and spines, only have spines, without warts and spines, with its proportion being 9:3:4. This result indicated the epistatic recessiveness of glgl gene to Tu_ gene. Combining the bulked segregant analysis (BSA) and the sequence-related amplified polymorphism (SRAP) technology, we found two markers linking to the Gl/gl locus. Among them, the one closely linked SRAP markers flanking the Gl/gl locus were marker ME4EM3 with 3.2cM, and then this marker transform to SCAR markers. A BAC library of cucumber will be PCR screened by this marker and get positive BAC clones with end sequence. This work is base for further fine mapping and isolated gene of fruit spine formation.To identify genes involved in the molecular control of cucumber fruit spine formation, we isolated one putative homologues of the Arabidopsis trichome associated gene TRANSPARENT TESTA GLABRA1 (TTG1). CsTTG1 genes are expressed in many tissues throughout the plant with RT-PCR analysis, including shoot apices and floral buds. The gene used in turn to probe Southern blots of cucumber genomic DNA restricted with various endonucleases. This result showed that cucumber genome contains single copy of CsTTG1 gene.This cucumber TTG1-like gene was able to restore trichome formation in ttg1 mutant Arabidopsis plants. These results indicate that these cotton genes may be functional homologues of AtTTG1. These results helpful understand molecular mechanism about muticelluar trichome pattern.