A glycine-rich RNA-binding protein can mediate physiological responses in transgenic plants under salt stress.
ABSTRACT Glycine-rich RNA-binding proteins (GRPs) are involved in post-transcriptional regulation of genes, which have been found to play a role in stress response. However, whether GRPs can mediate some physiological responses related to salt stress tolerance is still not known. In the present study, we investigated the role of GRPs in salt stress-induced physiological responses by generating transgenic tobacco lines overexpressing a GRP (LbGRP1) gene from Limonium bicolor (Bunge) Kuntze. Compared with wild type (WT) tobacco, the transgenic plants showed significantly improved superoxide dismutase and catalase activities under salt stress conditions. Levels of proline in the transgenic plants were significantly higher than those in the WT plants grown under NaCl stress conditions. Furthermore, Na(+) content and Na(+)/K(+) ratio in the transgenic plants were lower than those in the WT plants under both normal growth and stress conditions. These results suggested that overexpression of the LbGRP1 gene can affect some physiological processes associated with salt tolerance of plants. Therefore, we hypothesize that LbGST1 can enhance stress resistance by mediating some physiological pathways.
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ABSTRACT: Despite the fact that cold shock domain proteins (CSDPs) and glycine-rich RNA-binding proteins (GRPs) have been implicated to play a role during the cold adaptation process, their importance and function in eukaryotes, including plants, are largely unknown. To understand the functional role of plant CSDPs and GRPs in the cold response, two CSDPs (CSDP1 and CSDP2) and three GRPs (GRP2, GRP4 and GRP7) from Arabidopsis thaliana were investigated. Heterologous expression of CSDP1 or GRP7 complemented the cold sensitivity of BX04 mutant Escherichia coli that lack four cold shock proteins (CSPs) and is highly sensitive to cold stress, and resulted in better survival rate than control cells during incubation at low temperature. In contrast, CSDP2 and GRP4 had very little ability. Selective evolution of ligand by exponential enrichment (SELEX) revealed that GRP7 does not recognize specific RNAs but binds preferentially to G-rich RNA sequences. CSDP1 and GRP7 had DNA melting activity, and enhanced RNase activity. In contrast, CSDP2 and GRP4 had no DNA melting activity and did not enhance RNAase activity. Together, these results indicate that CSDPs and GRPs help E.coli grow and survive better during cold shock, and strongly imply that CSDP1 and GRP7 exhibit RNA chaperone activity during the cold adaptation process.Nucleic Acids Research 02/2007; 35(2):506-16. · 8.28 Impact Factor
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ABSTRACT: We screened a rice (Oryza sativa L. 'Nipponbare') full-length cDNA expression library through functional complementation in yeast (Saccharomyces cerevisiae) to find novel cation transporters involved in salt tolerance. We found that expression of a cDNA clone, encoding the rice homolog of Shaker family K(+) channel KAT1 (OsKAT1), suppressed the salt-sensitive phenotype of yeast strain G19 (Deltaena1-4), which lacks a major component of Na(+) efflux. It also suppressed a K(+)-transport-defective phenotype of yeast strain CY162 (Deltatrk1Deltatrk2), suggesting the enhancement of K(+) uptake by OsKAT1. By the expression of OsKAT1, the K(+) contents of salt-stressed G19 cells increased during the exponential growth phase. At the linear phase, however, OsKAT1-expressing G19 cells accumulated less Na(+) than nonexpressing cells, but almost the same K(+). The cellular Na(+) to K(+) ratio of OsKAT1-expressing G19 cells remained lower than nonexpressing cells under saline conditions. Rice cells overexpressing OsKAT1 also showed enhanced salt tolerance and increased cellular K(+) content. These functions of OsKAT1 are likely to be common among Shaker K(+) channels because OsAKT1 and Arabidopsis (Arabidopsis thaliana) KAT1 were able to complement the salt-sensitive phenotype of G19 as well as OsKAT1. The expression of OsKAT1 was restricted to internodes and rachides of wild-type rice, whereas other Shaker family genes were expressed in various organs. These results suggest that OsKAT1 is involved in salt tolerance of rice in cooperation with other K(+) channels by participating in maintenance of cytosolic cation homeostasis during salt stress and thus protects cells from Na(+).Plant physiology 09/2007; 144(4):1978-85. · 6.56 Impact Factor
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ABSTRACT: Proline (Pro) accumulation has been correlated with tolerance to drought and salinity stresses in plants. Therefore, overproduction of Pro in plants may lead to increased tolerance against these abiotic stresses. To test this possibility, we overexpressed in tobacco the mothbean [delta]-pyrroline-5-carboxylate synthetase, a bifunctional enzyme able to catalyze the conversion of glutamate to [delta]-pyrroline-5-carboxylate, which is then reduced to Pro. The transgenic plants produced a high level of the enzyme and synthesized 10- to 18-fold more Pro than control plants. These results suggest that activity of the first enzyme of the pathway is the rate-limiting factor in Pro synthesis. Exogenous supply of nitrogen further enhanced Pro production. The osmotic potentials of leaf sap from transgenic plants were less decreased under water-stress conditions compared to those of control plants. Overproduction of Pro also enhanced root biomass and flower development in transgenic plants under drought-stress conditions. These data demonstrated that Pro acts as an osmoprotectant and that overproduction of Pro results in the increased tolerance to osmotic stress in plants.Plant physiology 09/1995; 108(4):1387-1394. · 6.56 Impact Factor