Su, Pai-Hsiang , Li, Hsou-min .
Arabidopsis stromal Hsp70s are essential for plant development and important for seed thermotolerance.
Heat shock protein 70s (Hsp70s) have been shown to function in protein folding, protein translocation, and stress responses in almost all organisms and all subcellular compartments. However, the function of plastid stromal Hsp70s in higher plants are still uncertain. Genomic surveys revealed that there are two putative stromal Hsp70s in Arabidopsis, which were denoted cpHsc70-1 and cpHsc70-2. In this study, we show that cpHsc70-1 and cpHsc70-2 could indeed be imported into the chloroplast stroma. Their corresponding T-DNA-insertion knockout mutants were isolated and designated as Δcphsc70-1 and Δcphsc70-2. Δcphsc70-1 mutant plants exhibited variegated cotyledons, malformed leaves, growth retardation and impaired root growth. In contrast, no visible phenotype was observed in the Δcphsc70-2 mutant plants under normal growth conditions. However, no Δcphsc70-1 Δcphsc70-2 double mutant could be obtained, suggesting that the double mutation is lethal and stromal Hsp70s are essential for plant development. When analyzed using in vitro protein import assays, isolated Δcphsc70-2 chloroplasts had normal protein import ability compared to the wild-type chloroplasts, while reduced import was observed in chloroplasts isolated from 7-d-old Δcphsc70-1 cotyledons, but not chloroplasts isolated from mature leaves. Furthermore, after heat-shock treatments of seeds, the root growth of heated Δcphsc70-1 seeds was greatly impaired. These results indicate that cpHsc70-1 is important for seed thermotolerance and may also be involved in protein import into chloroplasts.
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1 - Academia Sinica, Institute of Molecular Biology, Nankang, Taipei, 11529, Taiwan
2 - Academia Sinica, Institute of Molecular Biology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM