J Integr Plant Biol. ›› 2017, Vol. 59 ›› Issue (2): 134-153.DOI: 10.1111/jipb.12510

Special Issue: Rice Genomics and Agriculture

• Plant Reproduction Biology • Previous Articles    

GRAIN INCOMPLETE FILLING 2 regulates grain filling and starch synthesis during rice caryopsis development

Xiangjin Wei1†, Guiai Jiao1,2†, Haiyan Lin1,3, Zhonghua Sheng1, Gaoneng Shao1, Lihong Xie1, Shaoqing Tang1, Qingguo Xu2* and Peisong Hu1**   

  1. 1State Key Laboratory of Rice Biology, Key Laboratory of Rice Biology and Breeding of Ministry of Agriculture, China National Rice Research Institute, Hangzhou 310006, China
    2College of Agronomy, Hunan Agricultural University, Changsha 410128, China
    3Agricultural Genomes Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China
  • Received:2016-09-21 Accepted:2016-12-12 Published:2016-12-13
  • About author:These authors contributed equally to this work
    ***Correspondence: ((Dr.Hu is fully responsible for the distribution of all materials associated with this article) E-mail: Qingguo Xu (huxu0309@aliyun.com), Peisong Hu (peisonghu@126.com; hupeisong@caas.cn)

Abstract:

Rice grain filling determines grain weight, final yield and grain quality. Here, a rice defective grain filling mutant, gif2, was identified. Grains of gif2 showed a slower filling rate and a significant lower final grain weight and yield compared to wild-type. The starch content in gif2 was noticeably decreased and its physicochemical properties were also altered. Moreover, gif2 endosperm cells showed obvious defects in compound granule formation. Positional cloning identified GIF2 to encode an ADP-glucose pyrophosphorylase (AGP) large subunit, AGPL2; consequently, AGP enzyme activity in gif2 endosperms was remarkably decreased. GIF2 is mainly expressed in developing grains and the coded protein localizes in the cytosol. Yeast two hybrid assay showed that GIF2 interacted with AGP small subunits OsAGPS1, OsAGPS2a and OsAGPS2b. Transcript levels for granule-bound starch synthase, starch synthase, starch branching enzyme and starch debranching enzyme were distinctly elevated in gif2 grains. In addition, the level of nucleotide diversity of the GIF2 locus was extremely low in both cultivated and wild rice. All of these results suggest that GIF2 plays important roles in the regulation of grain filling and starch biosynthesis during caryopsis development, and that it has been preserved during selection throughout domestication of modern rice.

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