Gene induction and repression by salt treatment in roots of the salinity-sensitive Chinese Spring wheat and the salinity-tolerant Chinese Spring × Elytrigia elongata amphiploid

Abstract

An artificial amphiploid from a cross between salinity-sensitive bread wheat cultivar Chinese Spring and highly tolerant Elytrigia elongata (Host) Nevski (= Agropyron elongatum Host) shows enhanced salinity tolerance relative to Chinese Spring. Poly(A)+ RNA was isolated from roots, expanding leaves, and old leaves from amphiploid and Chinese Spring plants prior to and after acclimation to high levels of NaCl in solution cultures. Two-dimensional gel electrophoresis of the in vitro translation products was used to compare these mRNA populations. The amphiploid had 10 mRNA species induced or enhanced and 8 species repressed in root tissue during acclimation to saline growth conditions. These 18 transcripts affected by salt treatment were also detected in wheat roots, but only 4 of these were similarly regulated. In Chinese Spring the acclimation to saline stress resulted in a marked change in the level of expression of 34 transcripts in root tissue; of these, 26 were detected in the amphiploid and only 6 were regulated as in the amphiploid. No differences were seen in gene expression between salt-treated and control plants in leaves and meristematic crowns and unexpanded leaves of the amphiploid.A number of species of the genus Elytrigia (= Agropyron sensu lato) are known to be highly salt tolerant (1, 2). Some naturally occur in the littoral zones and salt marshes of the Mediterranean and Black Sea regions. Since they are related to cultivated wheats, there has been interest in them as a source of genes for the improvement of salinity tolerance of these crops. An octoploid amphiploid has been derived from a cross between Elytrigia elongata Host (2n = 2x = 14) and hexaploid Triticum aestivum L. cv. Chinese Spring (2n = 6x = 42). From this amphiploid extensive stocks of E. elongata chromosome additions and substitution to T. aestivum have been obtained (3-6). This amphiploid has been shown to be highly tolerant to excessive levels of Na+, Cl-, Mg2+, So42-, and sea salt (7), and several of the chromosome addition and substitution lines have been shown to be more salinity tolerant than Chinese Spring (J.D., unpublished). The expression of this tolerance in a T. aestivum background is highly fortuitous, as many desirable traits of wheat relatives are not expressed in artificial amphiploids, most likely because of the hexaploidy of T. aestivum. The expression of salinity tolerance of E. elongata and related Elytrigia pontica (Pobp.) Holub in wheat backgrounds (7,8) indicates that tolerance is genetically dominant over sensitivity and that Elytrigia genes could be useful for the improvement of salinity tolerance not only of cultivated wheats but possibly of other grasses, especially in light of the recent report of successful transformation of monocotyledenous species (9).The underlying physiological mechanisms of the salinity tolerance of Elytrigia are poorly understood, but, in general, even highly salt-tolerant species are observed to have reduced growth rates when cultured under saline stress (for review, se...

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

“…Changes in gene expression have been demonstrated in salt stressed plants (8,19,22) and following other environmental stimuli such as heat shock and anaerobiosis (7,12). A correlation has been suggested between some responses (14) and induced or endogenously regulated changes in hormones (22).…”

“…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.…”

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).…”

Differential Two-Dimensional Protein Patterns as Related to Tissue Specificity and Water Conditions in Brassica napus var oleifera Root System

“…In roots and shoots of barley seedlings, distinct proteins and mRNAs, unique to each tissue, were induced by salinity stress (17,18), whereas, in wheat, only root tissues exhibited changes in gene expression, in both salt-tolerant and salt-sensitive genotypes (12).…”

“…It is also extensively documented that environmental stress promotes important modifications in gene expression (16,19), and tissue specificity of the stress response has been investigated under heat shock (2,4) osmotic (3,7), and salinity stress (12,17,18). Nevertheless, there seems to be no report of interaction between differential tissue-specific and differential drought stress-specific gene expression.…”