Differential mRNA transcription during salinity stress in barley

Abstract

The molecular and genetic bases of salinity tolerance in plants are not understood. Gene expression at the mRNA level was investigated in a salt-tolerant and a saltsensitive genotype of barley. Seedlings were exposed to NaCl stress and translatable mRNAs were isolated from root and shoot tissues. A reticulocyte cell-free system was programed with barley mRNAs and the in vitro products were resolved on two-dimensional polyacrylamide gels following isoelectric focusing or nonequilibrium pH gradient gel electrophoresis in the first dimension. The functional mRNAs in unstressed seedlings were qualitatively almost indistinguishable in the two genotypes. However, salinity stress triggered differential transcription of specific mRNAs depending upon genotype and tissue. In roots, 12 new mRNAs were induced that encoded proteins of 21-34 kDa, with a pI range of 6.1-7.7. In shoots, the 9 new mRNAs coded for proteins of 18-50.5 kDa, with a pI range of 5.4-7.8. These new stress mRNAs represented one of two main classes. Class I consisted of mRNAs shared by both genotypes. Class II represented mRNAs specific to each genotype; unique mRNAs of roots accumulated preferentially in the salt-tolerant genotype, whereas those of shoots accumulated in the saltsensitive genotype. The findings suggest that transcriptional as well as posttranscriptional mechanisms regulate gene expression in barley during salinity stress.Presently, the molecular basis of plant resistance to environmental stress is not understood. Altered gene expression due to heat, cold, and anaerobic stresses has been demonstrated in many higher plants (1-3). Salinity is an important limitation to crop production in many agricultural areas (4) but investigations on its molecular effects are scant (5-7). Variation in salinity tolerance has been observed in many plants (8)(9)(10)(11)), yet the underlying molecular and genetic factors have not been identified.Cultivated barley is one of the best known salt-tolerant crops. Epstein et al. (12) identified a few salt-tolerant cultivars by screening >7000 entries. Two contrasting genotypes, CM72, a salt-tolerant cultivar derived from the original California Mariout, and Prato, a salt-sensitive cultivar, were chosen in this study to define the molecular differences between them. The constitutive and salinity-induced differences of these the two genotypes are of interest. Recently, a comparison of gene expression in these two genotypes at the translational level revealed that salinity altered the newly synthesized protein patterns in a tissue-specific manner (13).Here, the responses of the two barley genotypes at the transcriptional level are presented. Functional mRNAs were isolated from seedlings before and after exposure to salinity stress and their translational products were compared. I demonstrate that salinity stress induces unique genotypespecific transcriptional changes in mRNAs of root and shoot tissues. To my knowledge, a genotype-specific regulation of gene expression by environmental stress has not been show...

Time Course of mRNA Induction Elicited by Salt Stress in the Common Ice Plant (Mesembryanthemum crystallinum)

“…Several other groups are involved in similar work (8,9,19,22) using a slightly different approach in so far as they study gene expression in either salt adapted lines of glycophytes or the differences in gene expression between salt tolerant and sensitive genetic variants. One important character by which salt sensitive plants differ from halophytes as well as from the selected cell culture lines and salt tolerant cultivars is that glycophytes respond to salt stress by arrest of growth.…”

Methodology Characterization of a rice germin-like protein gene promoter

“…Hurkman et al (1994) and Hurkman and Tanaka (1996) were the 1st to report GLP induction in barley roots during salt stress. Earlier, Ramagopal (1987) in barley and Naqvi et al (2009) in rice observed the induction of apparently similar proteins during salt stress by two-dimensional electrophoresis, although they did not characterize these proteins by sequencing. It has also been reported that salt stress can enhance wheat germin promoter activity in transgenic tobacco Bernier, 1997, 1999).…”

Stable NaCl Tolerance of Tobacco Cells Is Associated with Enhanced Accumulation of Osmotin

“…The association between osmotin accumulation and stable NaCI tolerance indicates that cells with a stable genetic change affecting the accumulation of osmotin are selected during prolonged exposure to high levels of NaCI. This stable alteration in gene expression probably affects salt tolerance.NaCl stress evokes changes in the levels of several plant gene products (8,12,14,21,(24)(25)(26)(27)(28). Since none of these gene products have been shown to be unequivocally involved in physiological adaptation to NaCl stress, additional information on the regulation of their expression is needed (11).…”