FLOURY ENDOSPERM11-2 encodes plastid HSP70-2 involved with the temperature-dependent chalkiness of rice (Oryza sativa L.) grains
FLOURY ENDOSPERM11-2 encodes plastid HSP70-2 involved with the temperature-dependent chalkiness of rice (Oryza sativa L.) grains
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DOI：
10.1111/tpj.14752
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发表时间：
2020-04-18
期刊：
影响因子：
7.2
通讯作者：
Katsube-Tanaka, Tomoyuki
中科院分区：
文献类型：
--
作者：
Tabassum, Rehenuma;Dosaka, Tokinori;Katsube-Tanaka, Tomoyuki
水稻垩白病是水稻生产中经常发生的一种病害。由于气候变化，谷物成为一个严重的问题。然而，垩白的分子机制在很大程度上是未知的。本研究从1116个水稻品系的离子束诱变材料中分离到一个温敏型粉胚乳突变体11 -2（flo 11 -2）。flo 11 -2突变体在平均温度为28 ℃下生长时显示出比野生型显著更高的垩白度，但与在平均温度为24 ℃下生长的野生型的垩白度水平相似。全外显子组测序的flo 11 -2突变体显示三个致病基因的候选人，包括Os 12 g 0244100，它编码的质体定位的70 kDa的热休克蛋白2（cpHSP 70 -2）。flo 11 -2突变体的cpHSP 70 -2在ATP酶结构域的保守基序5中的第259位天冬氨酸被缬氨酸取代（D259 V）。表达野生型cpHSP 70 -2的转基因flo 11 -2突变体显示出比flo 11 -2突变体显著更低的垩白度。此外，cpHSP 70 -2的积累水平与垩白率呈负相关，表明cpHSP 70 -2是flo 11 -2突变体垩白的致病基因。与野生型相比，突变型的cpHSP 70 -2在V-max时的ATP酶活性降低了23%。DnaK缺陷型大肠杆菌细胞的生长在37 ℃下严重减少，但在野生型DnaK中没有。结果表明，flo 11 -2突变体的垩白与cpHSP 70 -2功能降低有关。
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 degrees C, but similar levels of chalkiness to the wild type grown under a mean temperature of 24 degrees 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 V-max 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 degrees 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.