Expression of sunflower low-molecular-weight heat-shock proteins during embryogenesis and persistence after germination: localization and possible functional implications

Abstract

We isolated and sequenced Ha hsp17.9, a DNA complementary (cDNA) of dry-seed stored mRNA that encodes a low-molecular-weight heat-shock protein (LMW HSP). Sequence analysis identified Ha hspl7.9, and the previously reported Ha hspl7.6, as cDNAs encoding proteins (HSP17.6 and H S P 17.9) which belong to different families of cytoplasmic LMW H S Ps. Using specific antibodies we observed differential expression of both proteins during zygotic embryogenesis under controlled environment, and a remarkable persistence of these LMW HSPs during germination. Immuno-blot analysis of HSP17.9 proteins in two-dimensional gels revealed that the polypeptides expressed in embryos were indistinguishable from LMW HSPs expressed in vegetative tissues in response to water deficit; but they appeared different from homologeous proteins expressed in response to thermal-stress. Tissue-print immunolocalization experiments showed that HSP17.9 and HSP17.6 were homogeneously distributed in every tissue of desiccation-tolerant dry seeds and young seedlings under non-stress conditions. These results demonstrate developmental regulation of specific, cytoplasmic, plant LMW HSPs, suggesting also their involvement in water-stress tolerance.

Constitutive expression of small heat shock proteins in vegetative tissues of the resurrection plant Craterostigma plantagineum

“…Their predicted amino acid se-quences matched that of members of two sHSP families classified as class I and class II cytosolic proteins [11]. In vegetative tissues, sHSPs have been shown to accumulate only in response to stress, and mostly under heat-shock conditions [24].…”

“…In the course of our studies on gene expression during late embryogenesis in sunflower, we isolated and characterized cDNAs encoding two seed-stored sHSPs, Ha HSP17.6 and Ha HSP17.9 [2,11]. Their predicted amino acid se-…”

“…Most studies of Craterostigma have focused on the characterization of genes induced by dehydration [21, 22]. Many of these genes show sequence homologies with genes abundantly expressed in desiccation-tolerant zygotic embryos [reviewed in 3, 4].In the course of our studies on gene expression during late embryogenesis in sunflower, we isolated and characterized cDNAs encoding two seed-stored sHSPs, Ha HSP17.6 and Ha HSP17.9 [2,11]. Their predicted amino acid se-…”

“…In the course of our studies on gene expression during late embryogenesis in sunflower, we isolated and characterized cDNAs encoding two seed-stored sHSPs, Ha HSP17.6 and Ha HSP17.9 [2,11]. Their predicted amino acid se-quences matched that of members of two sHSP families classified as class I and class II cytosolic proteins [11].…”

Dual regulation of a heat shock promoter during embryogenesis: stage‐dependent role of heat shock elements

“…Similar studies in plant systems are more limited and incomplete. Work from our laboratory and other groups has established the developmental regulation of sHSP genes during plant embryogenesis (Almoguera and Jordano, 1992;Coca et al, 1994;DeRocher and Vierling, 1994;Gyö rgyey et al, 1991;Zur Nieden et al, 1995) and male gametogenesis (reviewed by Mascarenhas and Crone, 1996). A crucial observation in plant systems is that not all sHSP genes that respond to heat stress are developmentally regulated.…”