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Rus etal High Na Arabidopsis accessions mapping HKT1

ABSTRACT: Background: Plants are sessile and therefore have developed mechanisms to adapt to their environment, including the soil mineral nutrient composition. Ionomics is a developing functional genomics strategy designed to rapidly identify the genes and gene networks involved in regulating how plants acquire and accumulate these mineral nutrients from the soil. Here we report on the coupling of high-throughput elemental profiling of shoot tissue from various Arabidopsis accessions with DNA microarray-based bulk segregant analysis (BSA) and reverse genetics, for the rapid identification of genes from wild populations of Arabidopsis that are involved in regulating how plants acquire and accumulate Na+ from the soil. Methodology/Principal Findings: Elemental profiling of shoot tissue from 12 different Arabidopsis accessions revealed that Ts-1 and Tsu-1 accumulate higher shoot levels of Na+ than Col-0 and other accessions. We identify AtHKT1, known to encode a Na+ transporter, as being the causal locus driving elevated shoot Na+ in both Ts-1 and Tsu-1. Furthermore, we establish that a deletion in a tandem repeat sequence ~5 kb upstream of AtHKT1 is responsible for the reduced root expression of AtHKT1 observed in these accessions. Reciprocal grafting experiments establish that this loss of AtHKT1 expression in roots is responsible for elevated shoot Na+. Interestingly, and in contrast to the hkt1-1 null mutant, under NaCl stress conditions this novel AtHKT1 allele not only does not confer NaCl sensitivity, but co-segregates with elevated NaCl tolerance. We also present all our elemental profiling data in a new open access ionomics database, the Purdue Ionomics Information Management System (PiiMS; www.purdue.edu/dp/ionomics). Conclusions/Significance: Using DNA microarray-based genotyping has allowed us to rapidly identify AtHKT1 as the causal locus driving the natural variation in shoot Na+ accumulation we observed in Ts-1 and Tsu-1, two coastal populations of Arabidopsis. Such an approach overcomes the limitations imposed by a lack of established genetic markers in most Arabidopsis accessions, and opens up a vast and tractable source of natural variation for the identification of gene function not only in ionomics but also in many other biological processes. Keywords: genomics hybridization bulk segregant analysis

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE6203 | GEO | 2006/11/18

SECONDARY ACCESSION(S): PRJNA100693

REPOSITORIES: GEO

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Project description:Background:; Plants are sessile and therefore have developed mechanisms to adapt to their environment, including the soil mineral nutrient composition. Ionomics is a developing functional genomics strategy designed to rapidly identify the genes and gene networks involved in regulating how plants acquire and accumulate these mineral nutrients from the soil. Here we report on the coupling of high-throughput elemental profiling of shoot tissue from various Arabidopsis accessions with DNA microarray-based bulk segregant analysis (BSA) and reverse genetics, for the rapid identification of genes from wild populations of Arabidopsis that are involved in regulating how plants acquire and accumulate Na+ from the soil. Methodology/Principal Findings:; Elemental profiling of shoot tissue from 12 different Arabidopsis accessions revealed that Ts-1 and Tsu-1 accumulate higher shoot levels of Na+ than Col-0 and other accessions. We identify AtHKT1, known to encode a Na+ transporter, as being the causal locus driving elevated shoot Na+ in both Ts-1 and Tsu-1. Furthermore, we establish that a deletion in a tandem repeat sequence ~5 kb upstream of AtHKT1 is responsible for the reduced root expression of AtHKT1 observed in these accessions. Reciprocal grafting experiments establish that this loss of AtHKT1 expression in roots is responsible for elevated shoot Na+. Interestingly, and in contrast to the hkt1-1 null mutant, under NaCl stress conditions this novel AtHKT1 allele not only does not confer NaCl sensitivity, but co-segregates with elevated NaCl tolerance. We also present all our elemental profiling data in a new open access ionomics database, the Purdue Ionomics Information Management System (PiiMS; www.purdue.edu/dp/ionomics). Conclusions/Significance:; Using DNA microarray-based genotyping has allowed us to rapidly identify AtHKT1 as the causal locus driving the natural variation in shoot Na+ accumulation we observed in Ts-1 and Tsu-1, two coastal populations of Arabidopsis. Such an approach overcomes the limitations imposed by a lack of established genetic markers in most Arabidopsis accessions, and opens up a vast and tractable source of natural variation for the identification of gene function not only in ionomics but also in many other biological processes. Experiment Overall Design: Hybridizations from two sets of Bulk Segregant analysis. F2 populations from col-0 crossed to two High Na accessions: Ts-1 and Tsu-1 were analyzed. This series contains the 3 hybs from each accession that were used to identify Single Feature Polymorphisms, the 3 hybs of Col-0 they were compared to, and 1 hyb for each pool from the BSA mapping(High Na pool, low Na Pool).

Project description:These data provide a basis for exploration of gene expression differences between physiologically extreme accessions of Arabidopsis thaliana. Recent studies have documented remarkable genetic variation among Arabidopsis thaliana accessions collected from diverse habitats and across its geographical range. Of particular interest are accessions with putatively locally adapted phenotypes â i.e., accessions with attributes that are likely adaptive under the climatic or habitat conditions of their sites of origin. These genotypes are especially valuable as they may provide insight into the genetic basis of adaptive evolution as well as allow the discovery of genes of ecological importance. Therefore we studied the physiology, genome content and gene expression of two physiologically extreme accessions (Tsu-1 from a wet environment in Tsushima, Japan and Kas-1 from a dry environment in Kashmir, India). The gene expression studies were conducted under two levels of soil moisture and accompanied by physiological measurements to characterize early responses to soil moisture deficit. Genomic hybridization experiments identified 42,503 single feature polymorphisms (SFP) between accessions, providing an initial screen for putative SNPs, indels, or changes in gene content. Microarray transcript profiling of leaf RNA identified a large number (5,996) of genes exhibiting robust constitutive differences in expression including many genes involved in general growth and development as well as abiotic stress pathways. Interestingly, mild soil drying resulted in only subtle physiological responses but resulted in gene expression changes in hundreds of transcripts, including 352 genes exhibiting differential responses between accessions. Our results highlight the value of genomic studies of natural accessions as well as identify a number of candidate genes for the observed constitutive and induced physiological differences between Tsu-1 and Kas-1. The basic experimental design involves two accessions (Tsu-1 and Kas-1) crossed with two environmental levels (well-watered soil and mild soil drying) and 3 biological replicates per accession/treatment combination (2 x 2 x 6 =24 arrays total)

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Rus etal High Na Arabidopsis accessions mapping HKT1

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