I just off the phone will Roger Cheletat of the Tomato Resources Center here in Davis, California where I am staying at the moment. Unfortunately, he could only take enough time to return my call as he and his associates are busy with field trip preparations.
We talked in some detail about gene expression of (at), a recessive gene called (Apricot) which is noted for having yellow-pink flesh color. We also talked about gf, gs, and gr.
Apparently since they are curators of genes rather than breeders, the information we are seeking is not known offhand by Roger. It also seems that some of the genes I have been using have mutated since the phenotypes are not as the descriptors of those genes delineate.
Bi-colored fruits have been studied in the past, Roger states, but I will have to explore the database more completely before I talk with him again.
The high pigment genes are bouncing around in many of my creations, but I am too rusty right now to explain how I am using the enhanced expression for flesh colors. To give you some idea of the complexity of the subject see these links below.
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...gene carrying three tomato mutations that are in many respects isophenotypic to HP-1: high pigment-2 (hp-2), high pigment-2j (hp-2j) 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-1w 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-1w 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<LOD score<26, R2=62.8%). These results strongly support the hypothesis that DDB1 is the gene encoding the HP-1 and HP-1w mutant phenotypes.
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Plants respond to light by an array of developmental responses referred to as photomorphogenesis. Several photomorphogenic mutants were described in tomato. Among these, plants carrying the monogenic recessive high pigment (hp-1, hp-1w, hp-2, hp-2 j, and hp-2dg) mutations are characterized by an exaggerated light responsiveness. These mutants display shorter hypocotyls and higher anthocyanin levels in their seedlings, and share overall darker pigmentation of leaves and fruits. The increased pigmentation of fruits of these mutants is due to significantly elevated levels of carotenoids, primarily lycopene, in the mature fruit. Because of their effect on lycopene content, hp mutations were introgressed into several commercial tomato cultivars, marketed as Lycopene Rich Tomatoes (LRT). Initially, these hp mutations were marked as lesions in structural genes of the carotenoid biosynthetic pathway. However, studies have demonstrated that: 1) hp-2, hp-2 j, and hp-2dg represent different mutations in the gene encoding the nuclear protein DEETIOLATED1 (DET1), a negative regulator of photomorphogenesis; and 2) hp-1 and hp-1w represent mutations of the gene encoding UV DAMAGED DNA BINDING protein 1 (DDB1), a protein interacting genetically and biochemically with DET1. The discovery of det1 and ddb1 mutants in the tomato has therefore created a conceptual link between photomorphogenesis and over-production of fruit phytonutrients. Indeed, metabolite profiling, carried on fruits harvested from hp-2dg mutant plants, show that this mutant is characterized by overproduction of many metabolites; several of which are known for their antioxidant or photoprotective activities. This metabolite overproduction is associated with up-regulation of many genes, as determined by transcriptional profiling of fruits obtained from hp-2dg mutant plants in comparison to their isogenic normal controls.
In conclusion, our results demonstrate that manipulation of light signal transduction may be an effective approach towards improving the nutritional and functional quality of the tomato fruits
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When I find the time I will try to explain the above research in common language.
Tom Wagner