Characterization of a new tomato () T-DNA mutant allowed for the isolation of the () gene whose lack of function was responsible for the severe alterations observed in the shoot apex and reproductive organs under salinity conditions. Physiological studies proved that gene is required to maintain a proper low Na/Ca ratio in growing tissues allowing tomato growth under salt stress. Expression analysis of the main responsible genes for Na compartmentalization (i.e. ,, , [] and V-ATPase []) supported a reduced capacity to accumulate Na in mutant leaves, which resulted in a lower uploading of Na from xylem, allowing the toxic ion to reach apex and flowers. Likewise, the tomato and (), key genes for Ca fluxes to the vacuole, showed abnormal expression in plants indicating an impaired Ca release from vacuole. Additionally, complementation assay revealed that is a true ortholog of the Arabidopsis () gene, supporting that the essential function of CBL10 is conserved in Arabidopsis and tomato. Together, the findings obtained in this study provide new insights into the function of in salt stress tolerance. Thus, it is proposed that SlCBL10 mediates salt tolerance by regulating Na and Ca fluxes in the vacuole, cooperating with the vacuolar cation channel and the two vacuolar H-pumps, and, which in turn are revealed as potential targets of .

Recombination is a crucial component of evolution and breeding, producing new genetic combinations on which selection can act. Rates of recombination vary tremendously, not only between species but also within species and for specific chromosomal segments. In this study, by examining recombination events captured in recombinant inbred mapping populations previously created for maize, wheat, Arabidopsis, and mouse, we demonstrate that substantial variation exists for genomewide crossover rates in both outcrossed and inbred plant and animal species. We also identify quantitative trait loci (QTL) that control this variation. The method that we developed and employed here holds promise for elucidating factors that regulate meiotic recombination and for creation of hyperrecombinogenic lines, which can help overcome limited recombination that hampers breeding progress.A LTHOUGH natural selection is a powerful evolutionary process, it utilizes only the existing variation present in a population. Recombination of alleles is required to efficiently evolve new genetic varieties. Not surprisingly, theoretical predictions (Otto and Michalakis 1998) and empirical studies (Saleem et al. 2001) indicate that populations experiencing directional or strong selection pressures evolve increased recombination rates. Similarly to the natural evolutionary processes, combining many positive alleles into a single germplasm is the main objective of plant and animal breeding. The stacking of the favorable alleles is limited by the time and the number of meioses required to recombine numerous alleles from multiple parents. Consequently, a better understanding of the factors controlling recombination holds numerous implications for both academic and applied realms.To date, many of the genes involved in meiotic recombination have been identified and the mechanistic basis of recombination have begun to emerge (Krogh and Symington 2004;Cohen et al. 2006;Li and Ma 2006). However, the mechanisms that regulate recombination are poorly understood. Particularly, little is known about the control of genomewide recombination rates. Variation in recombination rates has been documented both within and between species, as well as between particular chromosomal regions (Rees 1961;Säll 1990;Beavis and Grant 1991;Tulsieram et al. 1992;Fatmi et al. 1993;Korol et al. 1994;Williams et al. 1995;Sanchez-Moran et al. 2002;Anderson et al. 2003;De Massy 2003;Myers et al. 2005; YandeauNelson et al. 2006). A minimum of one obligatory crossover per chromosome, or chromosome arm, occurs during meiosis as a requirement for proper chromosome segregation (Pardo-Manuel De Villena and Sapienza 2001). However, factors that control whether just this one or multiple crossovers occur per chromosome are poorly understood. Even though the idea that recombination frequencies can be genetically dissected, as any other quantitative trait, was first proposed long ago (Rasmusson 1927), to our knowledge, no quantitative trait loci (QTL) affecting recombination rates have been ...

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The sea aster, Aster tripolium L., grows naturally in temperate regions, mainly in the salt meadows close to the coast. The species is also found in naturally and anthropogenically salt-contaminated inland habitats, such as potash mine dumps. The genetic relationships among populations from different habitats and correlations of the genotype with physiological and vegetational parameters were investigated. A. tripolium plants from five different sites close to the seashore on the North Sea island Baltrum, from five different potash mine dumps and, as an outgroup, from the seashore in Japan were probed. DNA was extracted from five plants from each of the 11 A. tripolium populations and analyzed for random amplified polymorphic DNA (RAPD). Altogether 35 polymorphic bands in 51 individuals and 45 different detectable genotypes could be identified. For evaluation of the genetic variation using RAPD bands, the neighbor-joining method, the principal coordinate analysis, and the analysis of molecular variance were applied, resulting in the classification into three genetic groups. A. tripolium plants from different ecological habitats on Baltrum were closely related while the plants growing at the deposit dumps showed a higher genetic diversity. The Japanese population was genetically very different from the German populations. Correlations between phytosociological and soil parameters and the respective genotype were not significant. The results argue for a conservation of anthropogenically salt-contaminated habitats to maintain genetic variability not only on the species level, but also within a species.