Plant biology

Helping Plants Survive Heat Stress

Science's STKE  11 Sep 2007:
Vol. 2007, Issue 403, pp. tw333
DOI: 10.1126/stke.4032007tw333

Plants rely on microorganisms in the local environment for various important processes. One of the most commonly known is nitrogen fixation by symbiotic bacteria that colonize the roots of some plants. McLellan et al. provide evidence that fungi in the rhizosphere (the soil surrounding the roots of plants) may also contribute to heat tolerance. Previously, two inhibitors of mammalian heat shock protein 90 (HSP90) were discovered in extracts from Sonoran desert plant-associated fungi, McLellan et al. follow up on this result and show that one of these, monocillin I (MON), specifically binds and inhibits the chaperone activity of Arabidopsis HSP90 in vitro. Exposure of Arabidopsis seedlings to MON increased the expression and abundance of the heat shock response protein AtHSP101. Pretreatment of seedlings with MON before what would be a lethal heat stress in untreated plants increased the survival of the MON-exposed seedlings. The rescue of growth by MON required HSP101, consistent with MON’s triggering the heat shock response. When Arabidopsis seedlings were cultured with the fungus that produces MON, hypocotyl elongation was decreased compared with that in plants grown in the absence of MON; however, the plants tolerated heat stress much better in the presence of the fungus.

C. A. McLellan, T. J. Turbyville, E. M. K. Wijeratne, A. Kerschen, E. Vierling, C. Queitsch, L. Whitesell, A. A. L. Gunatilaka, A rhizosphere fungus enhances Arabidopsis thermotolerance through production of an HSP90 inhibitor. Plant Physiol. 145, 174-182 (2007). [Abstract] [Full Text]