Project Number: 1275-21000-172-04
Project Type:

Start Date: Nov 15, 2007
End Date: Nov 14, 2010

Objective:
Characterize at the molecular level the genomic location and role of the beta-modifier (MoB) gene in tomato. The research will focus on determining the physical location of the beta-modifier gene and positional cloning of beta-modifier. The mode by which MoB modulates fruit carotenoids will be assessed.

Approach:
Tomato populations developed for identification of molecular markers linked to Beta and MoB genes will be utilized to initiate studies for fine mapping and cloning of MoB. S. habrochaites-derived genotypes will be identified in segregating populations that express the Beta and MoB genes. To facilitate phenotyping and genotyping, selected genotypes will be introgressed into available S. pimpinellifolium accessions previously used to establish high density tomato linkage maps. In parallel, a double mutant Beta/ MoB will be crossed with S. lycopersicum (cv M82) introgression lines IL6-2 and IL6-3, in order to obtain F2 population segregating for MoB. Both populations will be screened with markers. A marker closely linked to MoB will be used to screen by DNA hybridization a tomato genomic library in BACs in order to identify the genomic DNA region. End of this BAC will be sequenced and used as probes for further screens. This "chromosome walking" will fill the gap surrounding MoB on chromosome 6. A minimal tiling path will be constructed from overlapping BACs and an appropriately sized contig will be identified for positional cloning of beta-modifier. Markers flanking beta-modifier will be used as starting points to sequence the region of interest. To identify potential genes in this region, clones containing open reading frames will be identified and assessed for sequence similarity to known genes. Proof of function for beta-modifier will be assessed using antisense silencing of the full length beta-modifier coding sequence in transgenic plants.