Molecular and Physiological Responses to Water Deficit in Drought-Tolerant and Drought-Sensitive Lines of Sunflower1

Abstract

To investigate correlations between phenotypic adaptation to water limitation and drought-induced gene expression, we have studied a model system consisting of a drought-tolerant line (R1) and a drought-sensitive line (S1) of sunflowers (Helianthus annuus L.) subjected to progressive drought. R1 tolerance is characterized by the maintenance of shoot cellular turgor. Drought-induced genes (HaElip1, HaDhn1, and HaDhn2) were previously identified in the tolerant line. The accumulation of the corresponding transcripts was compared as a function of soil and leaf water status in R1 and S1 plants during progressive drought. In leaves of R1 plants the accumulation of HaDhn1 and HaDhn2 transcripts, but not HaElip1 transcripts, was correlated with the drought-adaptive response. Drought-induced abscisic acid (ABA) concentration was not associated with the varietal difference in drought tolerance. Stomata of both lines displayed similar sensitivity to ABA. ABA-induced accumulation of HaDhn2 transcripts was higher in the tolerant than in the sensitive genotype. HaDhn1 transcripts were similarly accumulated in the tolerant and in the sensitive plants in response to ABA, suggesting that additional factors involved in drought regulation of HaDhn1 expression might exist in tolerant plants.Whole plants respond to drought through morphological, physiological, and metabolic modifications occurring in all plant organs. At the cellular level plant responses to water deficit may result from cell damage, whereas other responses may correspond to adaptive processes. Although a large number of drought-induced genes have been identified in a wide range of plant species, a molecular basis for plant tolerance to water stress remains far from being completely understood (Ingram and Bartels, 1996). The rapid translocation of ABA in shoots via xylem flux and the increase of ABA concentration in plant organs correlate with the major physiological changes that occur during plant response to drought (Zeevaart and Creelman, 1988). It is widely accepted that ABA mediates general adaptive responses to drought. However, there is evidence suggesting that additional signals are involved in this process (Munns and King, 1988; Trejo and Davies, 1991; Munns et al., 1993; Griffiths and Bray, 1996).Six cDNAs corresponding to transcripts up-regulated by water stress were isolated previously from a droughttolerant sunflower (Helianthus annuus L.) line, R1 (Ouvrard et al., 1996). Comparison of the steady-state level of transcripts between the R1 line and a closely related droughtsensitive line, S1, has shown that three of those transcripts (HaElip1, HaDhn1, and HaDhn2) were differently accumulated in tolerant compared with sensitive plants during water deficit. In response to exogenous ABA in leaves of the R1 genotype, HaDhn1 and HaDhn2 transcripts were up-regulated and the steady-state level of HaElip1 transcripts was not modified (Ouvrard et al., 1996). HaDhn1-and HaDhn2-deduced proteins belong to the dehydrin family, and HaElip1 is a related homolog of ea...

Changes in gene expression in maize kernel in response to water and salt stress

“…At the cellular level, water deficit may cause cellular damage or initiate adaptive responses (Cellier et al 1998). The products of stress-inducible genes can be classified into two groups (Bray 1997;Hasegawa et al 2000).…”

Dehydrins in maritime pine (Pinus pinaster) and their expression related to drought stress response

“…These results suggest a clear relationship between dehydrin expression, in our case, PpinDhn3 and PpinDhn4, and drought stress (Fig. 6) using parameters such as water loss or Ψ nwpd , as described by other authors, e.g., Cellier et al (1998) and Volaire (2003).…”

Response of sunflower (Helianthus annuus L) genotypes to PEG-mediated water stress

“…Maintenance of favorable plant water relations is vital for the development of drought resistance in crop plants [27][28][29]. The water content in plant roots and leaves has been shown to be associated with drought tolerance in cultivated sunflower [30]. The results suggested that sunflower is sensitive to water deficiency during early vegetative stage, which could lead to severe loss in agricultural production of sunflower grown in drought conditions.…”