Summary Endosperm is the main storage organ in cereal grain and determines grain yield and quality. The molecular mechanisms of heat shock proteins in regulating starch biosynthesis and endosperm development remain obscure. Here, we report a rice floury endosperm mutant flo24 that develops abnormal starch grains in the central starchy endosperm cells. Map‐based cloning and complementation test showed that FLO24 encodes a heat shock protein HSP101, which is localized in plastids. The mutated protein FLO24T296I dramatically lost its ability to hydrolyze ATP and to rescue the thermotolerance defects of the yeast hsp104 mutant. The flo24 mutant develops more severe floury endosperm when grown under high‐temperature conditions than normal conditions. And the FLO24 protein was dramatically induced at high temperature. FLO24 physically interacts with several key enzymes required for starch biosynthesis, including AGPL1, AGPL3 and PHO1. Combined biochemical and genetic evidence suggests that FLO24 acts cooperatively with HSP70cp‐2 to regulate starch biosynthesis and endosperm development in rice. Our results reveal that FLO24 acts as an important regulator of endosperm development, which might function in maintaining the activities of enzymes involved in starch biosynthesis in rice.

中文翻译：

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FLOURY ENDOSPERM24 是一种热休克蛋白 101 (HSP101)，是水稻淀粉生物合成和胚乳发育所必需的

概括 胚乳是谷物的主要贮藏器官，决定着谷物的产量和品质。热休克蛋白调节淀粉生物合成和胚乳发育的分子机制仍不清楚。 在这里，我们报道了一种米粉胚乳突变体弗洛24在中央淀粉胚乳细胞中形成异常淀粉粒。基于图位的克隆和互补测试表明弗洛24编码热休克蛋白 HSP101，该蛋白位于质体中。突变蛋白FLO24T296I急剧丧失水解 ATP 和挽救酵母耐热缺陷的能力热休克蛋白104突变体。 这弗洛24当在高温条件下生长时，突变体会比正常条件下发育出更严重的粉质胚乳。 FLO24蛋白在高温下被显着诱导。 FLO24 与淀粉生物合成所需的几种关键酶发生物理相互作用，包括 AGPL1、AGPL3 和 PHO1。综合生化和遗传学证据表明，FLO24 与 HSP70cp-2 协同作用，调节水稻淀粉生物合成和胚乳发育。 我们的结果表明弗洛24作为胚乳发育的重要调节剂，可能有助于维持水稻淀粉生物合成所涉及的酶的活性。