YEAST HSP104 HOMOLOG RICE HSP110 IS DEVELOPMENTALLY-REGULATED AND STRESS-REGULATED

HSP104 plays a critical role in the development of thermotolerance in yeast cells. Rice (Oryza sativa L.) HSP110 (OsHSP110) is previously sh own to be an immunological homologue of yeast HSP104. This protein acc umulates in rice seedlings in response to heat shock. However, no such high temperature-induced accumulation of OsHSP110 was found in the to pmost leaf of 90-day-old (just prior to flowering) plants of the culti vated species of rice (Oryza sativa L.) in our earlier study. In this paper, we show that, at the comparable growth stage, leaves of O. aust raliensis accumulated this protein to a marginal extent in response to heat shock, while levels of HSP110 were either markedly declined or r emained unaltered in 14 other wild rice species. Further, different or gans of the mature cultivated rice plant accumulated differential leve ls of OsHSP110, constitutively as well as in response to heat shock. I n particular, upper portions of culm, grains and developing embryos sh owed significantly high constitutive levels of OsHSP110. Tissue print immunolocalization studies showed that OsHSP110 is distributed in the vascular bundles in the shoot tissues and in seeds it is specifically localized in the seed coat (outermost layer) only. Importantly, OsHSP1 10 accumulated in shoots of rice seedlings in response to salinity, de siccation and low temperature stress also; furthermore, salinity stres s (NaCl) caused nearly a three-fold higher accumulation of this protei n than high temperature stress. (C) 1997 Elsevier Science Ireland Ltd.