A chloroplast-targeted heat shock protein 70 (HSP70) contributes to the photoprotection and repair of photosystem II during and after photoinhibition.
AUTOR(ES)
Schroda, M
RESUMO
Dark-grown Chlamydomonas reinhardtii cultures that were illuminated at low fluence rates before exposure to high-light conditions exhibited a faster rate of recovery from photoinhibition than did dark-grown cells that were directly exposed to photoinhibitory conditions. This pretreatment has been shown to induce the expression of several nuclear heat shock protein 70 (HSP70) genes, including HSP70B, encoding a chloroplast-localized chaperone. To investigate a possible role of plastidic HSP70B in photoprotection and repair of photosystem II, which is the major target of photoinhibition, we have constructed strains overexpressing or underexpressing HSP70B. The effect of light stress on photosystem II in nuclear transformants harboring HSP70B in the sense or antisense orientation was monitored by measuring variable fluorescence, flash-induced charge separation, and relative amounts of various photosystem II polypeptides. Underexpression of HSP70B caused an increased light sensitivity of photosystem II, whereas overexpression of HSP70B had a protective effect. Furthermore, the reactivation of photosystem II after photoinhibition was enhanced in the HSP70B-overexpressing strain when compared with the wild type, both in the presence or absence of synthesis of chloroplast-encoded proteins. Therefore, HSP70B may participate in vivo both in the molecular protection of the photosystem II reaction centers during photoinhibition and in the process of photosystem II repair.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=144243Documentos Relacionados
- Photosystem II Regulation and Dynamics of the Chloroplast D1 Protein in Arabidopsis Leaves during Photosynthesis and Photoinhibition.
- Human heat shock protein 70 (hsp70) protects murine cells from injury during metabolic stress.
- Cloning of the Heat Shock Protein 70 (HSP70) Gene of Ehrlichia sennetsu and Differential Expression of HSP70 and HSP60 mRNA after Temperature Upshift
- Chloroplast-Targeted ERD1 Protein Declines but Its mRNA Increases during Senescence in Arabidopsis1
- Molecular identification and expression of heat shock cognate 70 (hsc70) and heat shock protein 70 (hsp70) genes in the Pacific oyster Crassostrea gigas