T. Giordani et al., Expression of a dehydrin gene during embryo development and drought stressin ABA-deficient mutants of sunflower (Helianthus annuus L.), PLANT MOL B, 39(4), 1999, pp. 739-748
The synthesis of a particular class of proteins, the dehydrins, is a common
response to drought in plants. Dehydrins are known to be synthesized by th
e cell in response to abscisic acid, which represents a link between enviro
nment and nuclear activity, though dehydrin genes may be expressed even con
stitutively. We have investigated the relationship between abscisic acid (A
BA) and accumulation of a dehydrin mRNA in sunflower, in which a dehydrin c
DNA (HaDhn1a) was isolated. Tn particular, we studied changes in the steady
-state level of dehydrin transcripts in two mutants for ABA synthesis and a
ccumulation: nd-1 tan albino, non-dormant and lethal mutant with a very low
ABA content and no ABA accumulation in response to stress) and w-1 (a wilt
y mutant, with reduced ABA accumulation) during embryo and plantlet develop
ment and drought stress. Differences between genotypes were observed throug
h embryogenesis: w-1 shows a lower content of dehydrin transcripts in the e
arly stages compared to control plants, indicating that ABA affects dehydri
n mRNA accumulation; however, dehydrin transcripts level appears independen
t of ABA content in late embryogenesis. Also during drought stress in w-1 a
dult leaves, ABA is not quantitatively related to the steady-state level of
the HaDhn1a transcripts. Finally, data on nd-1 mutant show a high level of
dehydrin transcripts after drought stress in plantlet cotyledons and leafl
ets. These results indicate the existence of two regulation pathways of HaD
hn1a transcripts accumulation, an ABA-dependent and an ABA-independent one,
which may have cumulative effects.