Regulation of gene expression by endogenous ABA in tomato plants

Simon Fraser University Department of Biological Sciences 8888 University Drive V5A 1S6 Burnaby BC Canada
Acta Physiologiae Plantarum (Impact Factor: 1.52). 12/1997; 19(4):405-418. DOI: 10.1007/s11738-997-0037-2

ABSTRACT In response to water deficit, endogenous abscisic acid (ABA) accumulates in plants. This ABA serves as a signal for a multitude
of processes, including regulation of gene expression. ABA accumulated in response to water deficit signals cellular as well
as whole plant responses playing a role in the pattern of gene expression throughout the plant. Although the function of genes
regulated by ABA during stress are currently poorly understood, a number of these genes may permit the plant to adapt to environmental

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    ABSTRACT: We surveyed nucleotide diversity at two candidate genes LeNCED1 and pLC30-15, involved in an ABA (abscisic acid) signalling pathway, in two closely related tomato species Solanum peruvianum and Solanum chilense. Our six population samples (three for each species) cover a range of mesic to very dry habitats. The ABA pathway plays an important role in the plants' response to drought stress. LeNCED1 is an upstream gene involved in ABA biosynthesis, and pLC30-15 is a dehydrin gene positioned downstream in the pathway. The two genes show very different patterns of nucleotide variation. LeNCED1 exhibits very low nucleotide diversity relative to the eight neutral reference loci that were previously surveyed in these populations. This suggests that strong purifying selection has been acting on this gene. In contrast, pLC30-15 exhibits higher levels of nucleotide diversity and, in particular in S. chilense, higher genetic differentiation between populations than the reference loci, which is indicative of local adaptation. In the more drought-tolerant species S. chilense, one population (from Quicacha) shows a significant haplotype structure, which appears to be the result of positive (diversifying) selection.
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    ABSTRACT: - ions and to some extent Cl - and SO 4 2 - of Mg 2+ and nutrient imbalance caused by excess of Na + and Cl - ions. Salinity stress response is multigenic, as a number of processes i n- volved in the tolerance mechanism are affected, such as var ious compatible solutes/osmolytes, polyamines, reactive oxygen species and antioxidant defence mecha- nism, ion transport and compartmentalization of inj u- rious ions. Various genes/cDNAs encoding proteins involved in the above-mentioned processes have been identified and isolated. The role of genes/cDNAs e n- coding proteins involved in regulating other genes/ pro- teins, signal transduction process involving hormones like ABA, JA and polyamines, and strategies to i mprove salinity stress tolerance have also been di scussed. EXCESS amount of salt in the soil adversely affects plant growth and development. Nearly 20% of the world's cul- tivated area and nearly half of the world's i rrigated lands are affected by salinity 1
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    ABSTRACT: In a higher plant, it is only a small proportion of cells within the root that exist in relation to the external salinity. Most cells in a plant are not exposed directly to the external salinity but to the result of how this interacts with the processes governing uptake and partitioning of ions in the plant as a whole. These are predictably different processes, at higher levels of organisation, than cell-based processes. The number, nature and chromosomal distribution of genes and regulatory elements affecting how a whole plant responds to salinity will determine both the strategy and the practicability of breeding for increased performance. While QTL for important traits for environmental stress response have been identified, there is little evidence as to the nature of the genetic information, other than in cold tolerance. The work on cold tolerance suggests the importance of signal perception and signalling pathways, but for salinity there is little indication of what genes might control or co-ordinate the response of whole plants to salinity. The identification of such genes by positional cloning alone is highly difficult with current mapping resolution. It is possible to use DNA markers for such genes without knowing what they are — but the transfer of markers across a range of genotypes may not be easy. It is proposed that the way forward is via the integration of map-based location of QTL and the identification of possible candidate genes via the increasing power of differential expression technologies such as micro-arrays.
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