FLOURY ENDOSPERM16Encoding a NAD‐dependent Cytosolic Malate Dehydrogenase Plays an Important Role in Starch Synthesis and Seed Development in Rice

First author: Xuan Teng; Affiliations: Nanjing Agricultural University (南京农业大学): Nanjing, China

Corresponding author: Jianmin Wan

Starch is the most important form of energy storage in cereal crops. Many key enzymes involved in starch biosynthesis have been identified. However, the molecular mechanisms underlying the regulation of starch biosynthesis are largely unknown. In this study, we isolated a novel floury endosperm rice (Oryza sativa) mutant flo16 with defective starch grain (SG) formation. The amylose (直链淀粉) content and amylopectin (支链淀粉) structure were both altered in the flo16 mutant. Map‐ased cloning and complementation tests demonstrated that FLO16 encodes a NAD‐dependent cytosolic malate dehydrogenase (CMDH). The ATP contents was decreased in the mutant, resulting in significant reductions in the activity of starch synthesis‐ elated enzymes. Our results indicated that FLO16 plays a critical role in redox homeostasis that is important for compound SG formation and subsequent starch biosynthesis in rice endosperm. Overexpression of FLO16 significantly improved grain weight, suggesting a possible application of FLO16 in rice breeding. These findings provide a novel insight into the regulation of starch synthesis and seed development in rice.

淀粉是谷类作物最重要的能量储存方式。目前已经鉴定了很多淀粉生物合成中的关键酶。然而，淀粉生物合成的分子调控机制还有很多细节有待探索。本文中，作者获得了一种新的粉状胚乳水稻突变体flo16，该突变体在淀粉粒的形成方面存在缺陷。flo16突变体中的直链淀粉含量和支链淀粉结构。作者通过图位克隆和互补试验揭示了FLO16编码了一个依赖于NAD的胞质苹果酸脱氢酶CMDH。突变体中的ATP含量降低，导致了淀粉合成相关酶活性的减弱。本文的结果显示FLO16在氧化还原稳态方面发挥重要作用，而氧化还原稳态对于水稻胚乳中淀粉粒形成和淀粉的生物合成是非常重要的。过表达FLO16能够显著增加水稻的籽粒重量，说明该基因能够用于水稻育种实践中。本文的发现揭示了一个水稻淀粉合成和种子发育的新的调控机制。

通讯：万建民 (http://rice.njau.edu.cn/info/1012/1049.htm)

个人简介：1982年，南京农业大学，农学学士；1985年，南京农业大学，作物遗传育种硕士；1995年，日本京都大学，农学博士。

研究方向：水稻优异基因挖掘和分子育种研究。

doi: https://doi.org/10.1111/pbi.13108

Journal: Plant Biotechnology Journal

First Published: March 12, 2019