Search of Novel Genes Involved in High Temperature Tolerance during Grain Filling of Rice

Abstract

Heat stress during grain filling stage causes low rice grain qualities such as transparency. To unravel the mechanism involved in the phenomenon, we conducted comparative transcriptomic and proteomic analyses using Yukinko-mai (heat stress tolerant) and Todoroki-wase (heat stress susceptible) cultivars. We found that superoxide dismutase (SOD) protein was strongly expressed in seed of Todoroki-wase, but constitutively expressed in Yukinko-mai at early stage of grain filling regardless the heat stress. To determine whether SOD gene involves in the heat stress tolerance mechanism, we generated transgenic rice plants. We found that rice-overexpressing SOD was markedly improved in grain quality compared with wild type. In contrast, SOD knocked-down rice became more susceptible to heat stress. We concluded that the SOD gene plays an important role in adaptation to heat stress in rice. In addition, we also discovered a few heat stress tolerant Koshihikari mutant lines, which probably gained the ability through gene disruption as a result of Tos17 insertion. Works are in progress to clarify the heat stress tolerance mechanism in these mutant lines.