Abstract
Relationship between rice quality and gene expression of heat shock proteins (HSPs) was examined using rice (Oryza sativa L.) plants, a heat sensitive cultivar Hatsuboshi and a heat tolerant cultivar Fusaotome. Under heat stress, fresh weigh of seeds of cv,. Hatsuboshi increased rapidly and peaked at 14 DAF, while that of cv. Fusaotome increased linearly and peaked at 21 DAF as same as the control seeds. After harvesting populations of higher quality of brown rice was 22.8% in Fusaotome while 5.1% in Hatsuboshi under heat treatment, while those were 76.0% in the former and 76.9% in the latter under optimal condition, respectively. Semi-quantitative RT-PCR using rice seeds showed that expression levels of ER-type HSP90, protein disulfide isomerase (PDI) and HSP26 were higher in Fusaotome than those in Hatsuboshi indicating that heat treatment induced up-regulation of HSPs in Hatsuboshi but not in Fusaotome at 7 and 14 DAF. The present data suggested that secretion- and plastid-related HSP are involved in sensitivity of kernel quality and filling process to heat treatment condition. We will also discuss the starch synthesis and digesting genes in relation to the rice kernel quality.
