The molecular chaperone activity of sHSP17.7 was investigated using catalase as a substrate. Recombinant sHSP17.7 had heat-stable chaperone properties that were capable of protecting stressed catalase from precipitation.
- Drought tolerance was assessed in the transgenic lines and wild-type plants by withholding water for 6 days for evaluation of the ability of plants to continue growth after water-stress treatments. Although no significant difference was found in water potential of seedlings between transgenic lines and wildtype plants at the end of drought treatments, only transgenic seedlings with higher expression levels of sHSP17.7 protein could regrow after rewatering. Similar results were observed in survival rates after treatments with 30% polyethylene glycol (PEG) 3640 for 3 days.
- After heating, the survival rate of sHSP17.7 cells was 2-fold higher than that of the control cells.
- Transgenic rice plants with increased levels of sHSP17.7 protein exhibited significantly increased thermotolerance compared to untransformed control plants. The level of increased thermotolerance was correlated with the level of increased sHSP17.7 protein in the transgenic plants.
- Western and Northern blot analyses showed higher expression levels of sHSP17.7 protein in three transgenic lines than in one transgenic line. Overproduction of sHSP17.7 could increase drought tolerance in transgenic rice seedlings. . Overexpression of sHSP17.7 in rice confers higher thermotolerance and UV-B resistance.
- sHSP17.7 was overexpressed in the rice cultivar ‘Hoshinoyume’, by Agrobacterium-mediated transformation, under the control of a CaMV 35S promoter.
- The transgenic rice plant with the highest constitutive expression of sHSP17.7 had significantly greater resistance to UV-B stress than untransformed control plants. Increase in the degree of resistance of transgenic plants to UV-B was accompanied by an increase in production of sHSP17.7 protein.
- Gene tree were conducted using the software Molecular Evolutionary Genetics Analysis (MEGA) Version 4.0 by the neighbor-joining method with pairwise deletion and the Poisson correction model.
- As shown in Figure 1, based on amino acids sequence homology, nine OsHSP genes were divided into three classes, among them OsHSP80.2, OsHSP74.8 and OsHSP50.2 belong to HSP90 family; OsHSP71.1, OsHSP58.7 and OsHSP23.7 belong to HSP70 family; OsHSP26.7, OsHSP17.0, OsHSP24.1 and OsHSP17.0 belong to sHSP family.
- Heat shock proteins (Hsps) belong to a class of proteins that are conserved in prokaryotes and eukaryotes and are especially abundant in plants. Hsps are highly expressed in plants and other organisms after being stimulated by high temperature and other stresses. The sHsps are much more abundant in higher plants than in other organisms.
- Expression of nine OsHSP genes was affected differentially by abiotic stresses and abscisic acid (ABA). All nine OsHSP genes were induced strongly by heat shock treatment, whereas none of them were induced by cold. The transcripts of OsHSP80.2, OsHSP71.1 and OsHSP23.7 were increased during salt tress treatment. Expression of OsHSP80.2 and OsHSP24.1 genes were enhanced while treated with 10% PEG. Only OsHSP71.1 was induced by ABA while OsHSP24.1 was suppressed by ABA. These observations imply that the nine OsHSP genes may play different roles in plant development and abiotic stress responses.
- According to their approximate molecular weights, HSPs are grouped into five families: HSP100s, HSP90s, HSP70s, HSP60s and sHSPs. Most HSPs function as molecular chaperones in maintaining homeostasis of protein folding and are thought to be responsible for the acquisition of thermo tolerance. It is believed that the accumulations of HSPs play a pivotal role in abiotic stress.
Labs working on this gene
- National Agricultural Research Center for Hokkaido Region, Hitsujigaoka 1, Toyohira-ku, Sapporo 062-8555, Japan
- Hokkaido Green-Bio Institute, Naganuma, Hokkaido 069-1301, Japan;
- Sato Y, Yokoya S. Enhanced tolerance to drought stress in transgenic rice plants overexpressing a small heat-shock protein, sHSP17. 7[J]. Plant cell reports, 2008, 27(2): 329-334.
- Murakami T, Matsuba S, Funatsuki H, et al. Over-expression of a small heat shock protein, sHSP17. 7, confers both heat tolerance and UV-B resistance to rice plants[J]. Molecular Breeding, 2004, 13(2): 165-175.
- Zou J, Liu A, Chen X, et al. Expression analysis of nine rice heat shock protein genes under abiotic stresses and ABA treatment[J]. Journal of plant physiology, 2009, 166(8): 851-861.
- Vierling E. The roles of heat shock proteins in plants[J]. Annual review of plant biology, 1991, 42(1): 579-620.
- Trent J D. A review of acquired thermotolerance, heat‐shock proteins, and molecular chaperones in archaea[J]. FEMS microbiology reviews, 1996, 18(2‐3): 249-258.