Details

Autor(en) / Beteiligte

• Tabassum, Rehenuma
• Dosaka, Tokinori
• Ichida, Hiroyuki
• Morita, Ryouhei
• Ding, Yifan
• Abe, Tomoko
• Katsube‐Tanaka, Tomoyuki

Titel

FLOURY ENDOSPERM11‐2 encodes plastid HSP70‐2 involved with the temperature‐dependent chalkiness of rice (Oryza sativa L.) grains

Ist Teil von

• The Plant journal : for cell and molecular biology, 2020-07, Vol.103 (2), p.604-616

Ort / Verlag

England: Blackwell Publishing Ltd

Erscheinungsjahr

2020

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Summary The frequent occurrence of chalky rice (Oryza sativa L.) grains becomes a serious problem as a result of climate change. The molecular mechanism underlying chalkiness is largely unknown, however. In this study, the temperature‐sensitive floury endosperm11‐2 (flo11‐2) mutant was isolated from ion beam‐irradiated rice of 1116 lines. The flo11‐2 mutant showed significantly higher chalkiness than the wild type grown under a mean temperature of 28°C, but similar levels of chalkiness to the wild type grown under a mean temperature of 24°C. Whole‐exome sequencing of the flo11‐2 mutant showed three causal gene candidates, including Os12g0244100, which encodes the plastid‐localized 70‐kDa heat shock protein 2 (cpHSP70‐2). The cpHSP70‐2 of the flo11‐2 mutant has an amino acid substitution on the 259th aspartic acid with valine (D259V) in the conserved Motif 5 of the ATPase domain. Transgenic flo11‐2 mutants that express the wild‐type cpHSP70‐2 showed significantly lower chalkiness than the flo11‐2 mutant. Moreover, the accumulation level of cpHSP70‐2 was negatively correlated with the chalky ratio, indicating that cpHSP70‐2 is a causal gene for the chalkiness of the flo11‐2 mutant. The intrinsic ATPase activity of recombinant cpHSP70‐2 was lower by 23% at Vmax for the flo11‐2 mutant than for the wild type. The growth of DnaK‐defective Escherichia coli cells complemented with DnaK with the D201V mutation (equivalent to the D259V mutation) was severely reduced at 37°C, but not in the wild‐type DnaK. The results indicate that the lowered cpHSP70‐2 function is involved with the chalkiness of the flo11‐2 mutant. Significance Statement The flo11‐2 mutant was isolated, and produces a high degree of chalkiness under a mean temperature of 28°C but shows a normal phenotype under a mean temperature of 24°C. Reduced ATPase and chaperone activities of plastid‐targeting 70‐kDa heat shock protein 2 (cpHSP70‐2), which are caused by the D259V mutation in its nucleotide binding domain, are involved in the temperature‐dependent chalky grain formation observed in the flo11‐2 rice mutant.