Molecular Analysis Of Yellow Flesh Formation In Tomato Accession PI114490

Carotenoids are a diverse group of colourful pigments naturally found in plants, algae, fungi and bacteria. They are accumulated in non-photosynthetic tissues such as fruits and flowers showing yellow, orange, and red colors in various plant species. Carotenoids are also important components of the human diet due to their high antioxidative potential. They play essential roles in development, photosynthesis and the production of phytohormones, such as abscisic acid. Understanding the mechanism of carotenoids biosynthesis is benefit to improve the qulity of crops and is important to comprehend the regulated mechanism of development for the plants.Chromoplast-specific phytoene synthase (PSY1) is generally considered as the most important regulatory enzyme in carotenoid biosynthesis pathway in fruit. The expression of Psyl gene determines the content of carotenoids in fruit. It has been shown that insertion of transposon in PSY1genome results in aberrant transcription of Psyl causing lack of carotenoids in fruit in yellow flesh tomato mutant (r). A S. lycopersicum var. cerasiforme accession PI114490with yellow flesh phenotype, which is conditioned by a gene allelic to the known r gene, has a complete genomic DNA sequence for the Psyl gene with one nucleotide difference in the fourth intron comparing to the wild type. In order to understanding the cause for the yellow-flesh phenotype in PI114490, we will do the following work:(1) testing the yellow flesh phenotype for PI114490by analyzing the carotenoids contents in fruit,(2) discovering the mRNA sequence of Psyl gene and analyzing the expression levels of this gene in different tissues,(3) investigating the relationship of linkage between the SNP and yellow-flesh phenotype in the F2population of PI114490×OH88119and the different lines tomato with yellow flesh phenotype, and functional analysis of the SNP, and (4) Identifing the mutant sequences neibouring of PSY1gene and the relationship of linkage to yellow-flesh phenotype.We showed here the results including the contents as following:(1) carotenoid contents of fruit in PI114409are in accordance with LA3532known being the yellow-flesh mutant.(2) We have identified two different transcript forms, a wide-type transcript (Psy1) and an abnormal transcript (Psy1/Unknown) with different3’end, existing in a yellow-fruited tomato accession PI114490. The PSYl/Unknown has a lower function than PSY1in a bacterial expression system due to the mutation of3’end. High expression of Psyl/Unknown dramatically inhibited the transcription of Psyl at the maturing stage of fruit and resulted in low accumulation of carotenoid and yellow flesh in PI114490.(3) The chimeric transcript Psy1/Unknown is generated by joining exons from two convergent genes, Psyl and an unknown gene, transcribed using both DNA complementary strands. It might be the product of trans-splicing reaction.(4) Two modified sites, a SNP and a SSR, in genomic DNA might being the cause of Psy1/Unknown generation, and (5) The SNP site in the forth intron could initiated alternative splicing to generated new splicing isoforms. The results will help to understand the effects of Psyl gene on fruit color and its regulation mechanisms, which aims to undercover the mechanisms of yellow flesh color formation and improves the knowledge of carotenoid biosynthesis pathway in tomato.