ps2, the gene responsible for functional sterility in tomato, due to non-dehiscent anthers, is the result of a mutation in a novel polygalacturonase gene

The recessive mutation ps-2, which appeared spontaneously in tomato, confers functional male sterility due to non-dehiscent anthers. In this study, we isolated and characterized the PS-2 gene. A single nucleotide mutation in a novel tomato polygalacturonase gene is responsible for the ps-2 phenotype. The mutation in ps-2 is responsible for an alternative splicing during maturation of the pre-mRNA, which leads to an aberrant mRNA. Differentiation between ps-2 and wild type (PS-2) anthers only appears in the final developmental stage in which the stomium remains closed in the mutant. To our knowledge, this is the first functional sterility gene isolated in the Solanaceae family. The specific expression of the Arabidopsis homolog of PS-2 in the anther dehiscence zone suggests a conserved mode of action over the plant kingdom, which means that the repression of PS-2 homologs may be a potential way to introduce functional sterility in other specie

Parthenocarpy and functional sterility in tomato

Parthenocarpy is the development of the fruit in absence of pollination and/or fertilization. In tomato (Solanum lycopersicum), parthenocarpy is considered as an interesting trait because it can improve fruit setting under environmental conditions that affect the viability of the pollen. Auxins and gibberellins are considered as the key players in parthenocarpic fruit development. An increased level of these hormones in the ovary can be a substitute for pollination and trigger fruit development. We characterized and mapped two sets of two parthenocarpy genes in two distinct tomato introgression lines carrying genome fragments of Solanum habrochaites (a related wild species of tomato). Tomato lines carrying these genes will produce seedless fruits in absence of pollination, and seeded fruits if the ovary is pollinated, thus affecting the uniformity of the production. The use of functional sterility in combination with parthenocarpy can overcome this problem of uniformity of seedless fruits production, but still allows seed production by hand pollination. The best functional sterility gene in tomato is likely to be the positional sterility-2 (ps-2) gene, which confers non-dehiscent anthers, containing viable pollen. We accurately determined the position of the ps-2 gene on the short arm of Chromosome 4. Subsequently, after the successful construction of a physical map in the ps-2 locus region, we isolated the ps-2 gene. The ps-2 phenotype appeared to be the result of a single nucleotide substitution in a novel tomato polygalacturonase gene, named TDPG (Tomato Dehiscence PolyGalacturonase). This single mutation affects one of the intron splicing recognition site, causing an alternative splicing of the mRNA, thus leading to an aberrant mRNA. The expression of this gene is specific to the dehiscent anthers and to a lesser degree to the mature fruit. The repression of TDPG homologs may be a potential way to introduce functional sterility in other species

Parthenocarpic fruit development in tomato

Parthenocarpic fruit development is a very attractive trait for growers and consumers. In tomato, three main sources of facultative parthenocarpy, pat, pat-2, pat-3/pat-4, are known to have potential applications in agriculture. The parthenocarpic fruit development in these lines is triggered by a deregulation of the hormonal balance in some specific tissues. Auxins and gibberellins are considered as the key elements in parthenocarpic fruit development of those lines. An increased level of these hormones in the ovary can substitute for pollination and trigger fruit development. This has opened up genetic engineering approaches for parthenocarpy that have given promising results, both in quality and quantity of seedless fruit productio

Parthenocarpic fruit development in tomato

Parthenocarpic fruit development is a very attractive trait for growers and consumers. In tomato, three main sources of facultative parthenocarpy, pat, pat-2, pat-3/pat-4, are known to have potential applications in agriculture. The parthenocarpic fruit development in these lines is triggered by a deregulation of the hormonal balance in some specific tissues. Auxins and gibberellins are considered as the key elements in parthenocarpic fruit development of those lines. An increased level of these hormones in the ovary can substitute for pollination and trigger fruit development. This has opened up genetic engineering approaches for parthenocarpy that have given promising results, both in quality and quantity of seedless fruit productio

High-resolution fine mapping of ps-2, a mutated gene conferring functional male sterility in tomato due to non-dehiscent anthers

Functional male sterility is an important trait for the production of hybrid seeds. Among the genes coding for functional male sterility in tomato is the positional sterility gene ps-2. ps-2 is monogenic recessive, confers non-dehiscent anthers and is the most suitable for practical uses. In order to have tools for molecular-assisted selection (MAS) we fine mapped the ps-2 locus. This was done in an F2 segregating population derived from the interspecific cross between a functionally male sterile line (ps-2/ps-2; Solanum lycopersicum) and a functionally male fertile line (S. pimpinellifolium). Here we report the procedure that has led to the high-resolution fine mapping of the ps-2 locus in a 1.65 cM interval delimited by markers T0958 and T0635 on the short arm of Chromosome 4. The presence of many COS markers in the local high-resolution map allowed us to study the synteny between tomato and Arabidopsis at the ps-2 locus region. No obvious candidate gene for ps-2 was identified among the known functional male sterility genes in Arabidopsi