Analyses on the molecular mechanism underlying the chalkiness of the rice mutant 13-45

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07571
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Crop production science
• Research Institution: Kyoto University
• Principal Investigator: Tanaka Tomoyuki (勝部朋之) 京都大学, 農学研究科, 准教授 (50224473)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: イネ / 白未熟粒 / 高温ストレス / 熱ストレスタンパク質 / 突然変異体

Outline of Final Research Achievements

High temperature during a grain filling of rice produces chalky grains which diminish grain quality as well as productivity. In this study, we analyzed the novel chalky rice mutant 13-45, the possible causal gene of which is plastid heat shock protein 70-2 (cpHsp70-2). In RNAseq analysis under high temperature, upregulation and downregulation of genes were detected for some heat stress proteins and seed storage proteins, respectively. The intrinsic ATPase activity of recombinant cpHsp70-2 was lower by 23% in the mutant type than the wild type. Besides, the growth of DnaK (Hsp70 homologue)-defective Escherichia coli (E. coli) cells complemented with DnaK with 13-45 type mutation was significantly reduced at 37 oC. The growth of DnaK-defective E. coli cells complemented with wild type DnaK was not reduced at 37 oC. Taken together, these results suggest that the lowered function of the cpHsp70-2 is involved with the chalkiness of the mutant 13-45.

Free Research Field

作物生産学

Academic Significance and Societal Importance of the Research Achievements

近年、イネ登熟期の高温・低日射により白未熟粒の発生が問題となっている。白未熟粒が増えると、外観品質が劣るだけでなく、食味の低下、精米歩留まりの低下による実質的な収量低下など、様々な負の影響をもたらす。そのため、白未熟粒発生機構を解明し、白未熟粒を生じにくい品種の育成や栽培技術の開発が求められる。本研究では、高温下でのみ著しく白未熟粒を生じる突然変異体13-45を用いて、その発生原因の解明を試みた。その結果、熱ストレスタンパク質の一種cpHsp70-2の機能低下が乳白化の原因であることが示唆された。本研究の成果は、野生型における白未熟粒発生機構の解明に向けて、有用な知見になると期待される。