Yeast HSP104 homologue rice HSP110 is developmentally- and stress-regulated

Abstract

HSP104 plays a critical role in the development of thermotolerance in yeast cells. Rice (Oryza sativa L.) HSP110 (OsHSP110) is previously shown to be an immunological homologue of yeast HSP104. This protein accumulates in rice seedlings in response to heat shock. However, no such high temperature-induced accumulation of OsHSP110 was found in the topmost leaf of 90-day-old (just prior to flowering) plants of the cultivated species of rice (Oryza sativa L.) in our earlier study. In this paper, we show that, at the comparable growth stage, leaves of O. australiensis accumulated this protein to a marginal extent in response to heat shock, while levels of HSP110 were either markedly declined or remained unaltered in 14 other wild rice species. Further, different organs of the mature cultivated rice plant accumulated differential levels of OsHSP110, constitutively as well as in response to heat shock. In particular, upper portions of culm, grains and developing embryos showed 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 seec coat (outermost layer) only. Importantly, OsHSP110 accumulated in shoots of rice seedlings in response to salinity, desiccation and low temperature stress also; furthermore, salinity stress (NaCl) caused nearly a three-fold higher accumulation of this protein than high temperature stress.