Genes encoding chitinase-antifreeze proteins are regulated by cold and expressed by all cell types in winter rye shoots.
ABSTRACT One group of antifreeze proteins (AFPs) is composed of two chitinases that accumulate in the apoplast of winter rye leaves during cold acclimation. In this study, the 28- and 35-kDa chitinase-AFPs were localized in nonacclimated and cold-acclimated rye leaves by immunoelectron microscopy with an antiserum produced against the purified winter rye 35-kDa chitinase-AFP. In cold-acclimated winter rye leaves, labelled chitinase-AFPs were abundant in the walls of epidermal, parenchymal sheath and mesophyll cells and xylem vessels, while less label was present in walls of vascular parenchyma cells. In contrast, chitinase labelling was essentially absent in the nonacclimated cells except in xylem vessels. As shown by RNA blotting, the transcripts of chitinase-AFPs accumulated to a high level in rye leaves during cold acclimation, to a lesser extent in crowns and were not detectable in roots. mRNA transcripts of the 28-kDa chitinase-AFP were localized in rye leaves by in situ hybridization. The chitinase-AFP transcripts were found in the same cell types as the protein itself. We conclude that all metabolically active cell types in cold-acclimated winter rye leaves and crowns are able to synthesize chitinase-AFPs and secrete them into adjacent cell walls, where they may interact with ice to delay its propagation through the plant and modify its growth.
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ABSTRACT: In a rat model, lithium treatment is associated with polyuria and severe downregulation of aquaporin-2 (AQP2) protein in the inner medulla (IM) or in the whole kidney. However, it is not known (1) to what extent this downregulation occurs at the mRNA level; (2) whether the main sodium transporter of the nephron, Na,K-ATPase, is regulated in parallel at the mRNA level, and (3) whether lithium treatment induces zonal or segmental differences in AQP2 and Na,K-ATPase mRNA levels. We examined the changes in mRNA expression levels for AQP2 and Na,K-ATPase in kidney cortex, inner stripe of the outer medulla (ISOM), and IM of rats treated with lithium orally using semiquantitative Northern blot analyses and in situ hybridization at the light and electron microscopic levels. The AQP2 mRNA levels decreased significantly (p < 0.01) in lithium-treated rats to 37 +/- 4% in the cortex, to 17 +/- 4% in the ISOM, and to 23 +/- 5% in the IM, while the Na,K-ATPase mRNA levels were not altered in the cortex, but were significantly (p < 0.05) altered in the ISOM (144 +/- 15% after 10 days, but 68 +/- 4% after 4 weeks) and in the IM (63 +/- 8% after 10 days, but normalized after 4 weeks). In situ hybridization showed reduced levels of AQP2 mRNA in all zones of the kidney, but the Na,K-ATPase mRNA expressions were slightly decreased only in IM collecting ducts. At the ultrastructural level, principal cells in the IM collecting ducts showed slight hypertrophy, but no cell damage after 4 weeks of lithium treatment. The results demonstrate substantial downregulation of AQP2 at the mRNA level throughout the collecting duct in experimental lithium-induced nephrogenic dabetes insipidus and moderately decreased Na,K-ATPase mRNA levels in the ISOM and in the IM. The results suggest that decreased mRNA expressions of AQP2 and Na,K-ATPase contribute to the development of lithium-induced nephrogenic diabetes insipidus.Nephron Experimental Nephrology 02/2004; 97(1):e1-16. · 2.01 Impact Factor
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ABSTRACT: Low temperature is one of the major limiting environmental factors which constitutes the growth, development, productivity and distribution of plants. Over the past several years, the proteins and genes associated with freezing resistance of plants have been widely studied. The recent progress of domestic and foreign research on plant antifreeze proteins and the identification and characterization of plant antifreeze protein genes, especially on expression regulatory mechanism of plant antifreeze proteins are reviewed in this paper. Finally, some unsolved problems and the trend of research in physiological functions and gene expression regulatory mechanism of plant antifreeze proteins are discussed.Forestry Studies in China 7(1):46-52.
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ABSTRACT: Plants in nature are generally resistant to most of the pathogens they encounter. However, many flingal pathogens can cause severe diseases and significant yield losses in crops. Plants defend themselves against pathogens through a combination of constitutive and inducible defenses. The induced plant defense is particularly characterized by an increased accumulation of pathogenesis-related proteins (PRs). Since the discovery of PRs in 1970, several PR families have been identified. The specific function of many PRs is still unknown, although several are postulated to play a role in preventing pathogen invasion. The aim of my research was to study spatial and temporal localization of PRs and accumulation of their corresponding mRNAs to better understand the role and possible function of PRs in plant defense. As a model system I studied the interaction between barley and the hemibiotrophic fungus Bipolaris sorokiniana, which causes severe yield losses worldwide. The studies are mainly focused on three PRs (PR-I, PR-3 and PR-5). These PRs accumulated in both leaves and roots of barley seedlings as a response to infection of the respective tissues. However, the accumulation of PRs in roots was dependent on whether young or old root segments were infected. A stronger response was found when young root segments were inoculated in comparison to old roots. All three PRs appear to be part of a prefoimed defense since both PR-I and PR-5 were constitutively present in both xylem and phloem tissues and the root epidermis, and PR-3 showed a high constitutive presence mainly in the epidermis of leaves and to some extent in the phloem. In response to infection, all three proteins were highly induced in the ground tissues and to some extent in the vascular tissues. PR-I, PR-3 and PR-5 mRNAs accumulated in a biphasic pattern in leaves from both leaf- and root-infected seedlings. This biphasic accumulation pattern of transcripts was not detectable in roots. These results suggest that different induction strategies may be active in barley seedlings depending on the primary site of infection by B. sorokiniana. PR-I, PR-3 and PR-S were all recovered over the cell walls of inter- and intracellular hyphae of B. sorokiniana indicating that they may influence fungal growth.