Distribution patterns of 104 kDa stress-associated protein in rice.

A 104 kDa protein (SAP 104) accumulates in rice seedlings in response to several abiotic stress conditions and immunological homologues of rice SAP 104 have been detected in several monocot and dicot species, as also Neurospora crassa, a fungus. In this report, we show that the amino acid sequence of a tryptic peptide generated from purified SAP 104 bears significant homology with an ATP-binding domain of the HSP 100 family proteins of Arabidopsis thaliana and Glycine max. It is further shown that differential uninduced and induced (by high-temperature stress) levels of this protein are accumulated in various organs of the mature rice plant grown under field conditions. Significant uninduced levels of this protein were in particular found in developing and mature rice grains. Seeds/grains of several other plant genera (i.e. Triticum aestivum, Zea mays, Brassica juncea) were also found to contain high uninduced levels of SAP 104. Importantly, the levels of uninduced SAP 104 in rice grains were found to decline during the seed germination phase: after two days of germination, this protein was undetectable in tissues representing pooled sample of seeds and just-emerged seedlings. Tissue print-immunoblotting analysis has indicated that in seeds high levels of this protein are specifically present in the embryo portion.