The tomato homolog of the gene encoding UV-damaged DNA binding protein 1 (DDB1) underlined as the gene that causes the high pigment-1 mutant phenotype

摘要

A tomato EST sequence, highly homologous to the human and Arabidopsis thaliana UV-damaged DNA binding protein 1 (DDB1), was mapped to the centromeric region of the tomato chromosome 2. This region was previously shown to harbor the HP-1 gene, encoding the high pigment-1 (hp-1) and the high pigment-1 w (hp-1 w ) mutant phenotypes. Recent results also show that the A. thaliana DDB1 protein interacts both genetically and biochemically with the protein encoded by DEETIOLATED1, a gene carrying three tomato mutations that are in many respects isophenotypic to hp-1: high pigment-2 (hp-2), high pigment-2 j (hp-2 j ) and dark green (dg). The entire coding region of the DDB1 gene was sequenced in an hp-1 mutant and its near-isogenic normal plant in the cv. Ailsa Craig background, and also in an hp-1 w mutant and its isogenic normal plant in the GT breeding line background. Sequence analysis revealed a single A931-to-T931 base transversion in the coding sequence of the DDB1 gene in the hp-1 mutant plants. This transversion results in the substitution of the conserved asparagine at position 311 to a tyrosine residue. In the hp-1 w mutant, on the other hand, a single G2392-to-A2392 transition was observed, resulting in the substitution of the conserved glutamic acid at position 798 to a lysine residue. The single nucleotide polymorphism that differentiates hp-1 mutant and normal plants in the cv. Ailsa Craig background was used to design a pyrosequencing genotyping system. Analysis of a resource F2 population segregating for the hp-1 mutation revealed a very strong linkage association between the DDB1 locus and the photomorphogenic response of the seedlings, measured as hypocotyl length (25