J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (7): 1782-1793.DOI: 10.1111/jipb.13488

• Molecular Physiology • Previous Articles     Next Articles

The kinase OsSK41/OsGSK5 negatively regulates amylose content in rice endosperm by affecting the interaction between OsEBP89 and OsBP5

Zejun Hu1,2†, Fuan Niu1,2†, Peiwen Yan2†, Kai Wang1, Lixia Zhang1, Ying Yan1, Yu Zhu2, Shiqing Dong2, Fuying Ma2, Dengyong Lan2, Siwen Liu2, Xiaoyun Xin2, Ying Wang2, Jinshui Yang2, Liming Cao1*, Shujun Wu1* and Xiaojin Luo2,3*   

  1. 1. Key Laboratory of Germplasm Innovation and Genetic Improvement of Grain and Oil Crops (Co‐construction by Ministry and Province), Ministry of Agriculture and Rural Affairs, Crop Breeding and Cultivation Research Institute, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China;
    2. State Key Laboratory of Genetic Engineering and MOE Engineering Research Center of Gene Technology, School of Life Sciences, Fudan University, Shanghai 200438, China;
    3. MOE Key Laboratory of Crop Physiology, Ecology and Genetic Breeding College of Agronomy, Jiangxi Agricultural University, Nanchang 330045, China
    These authors contributed equally to this work.
    *Correspondences: Xiaojin Luo (luoxj@fudan.edu.cn, Dr. Luo is fully responsible for the distributions of all materials associated with this article); Liming Cao (clm079@163.com); Shujun Wu (wushujun@saas.sh.cn)
  • Received:2022-10-17 Accepted:2023-03-23 Online:2023-03-25 Published:2023-07-01

Abstract: Amylose content (AC) is the main factor determining the palatability, viscosity, transparency, and digestibility of rice (Oryza sativa) grains. AC in rice grains is mainly controlled by different alleles of the Waxy (Wx) gene. The AP2/EREBP transcription factor OsEBP89 interacts with the MYC-like protein OsBP5 to synergistically regulate the expression of Wx. Here, we determined that the GLYCOGEN SYNTHASE KINASE 5 (OsGSK5, also named SHAGGY-like kinase 41 [OsSK41]) inhibits the transcriptional activation activity of OsEBP89 in rice grains during amylose biosynthesis. The loss of OsSK41 function enhanced Wx expression and increased AC in rice grains. By contrast, the loss of function of OsEBP89 reduced Wx expression and decreased AC in rice grains. OsSK41 interacts with OsEBP89 and phosphorylates four of its sites (Thr-28, Thr-30, Ser-238, and Thr-257), which makes OsEBP89 unstable and attenuates its interaction with OsBP5. Wx promoter activity was relatively weak when regulated by the phosphomimic variant OsEBP89E–OsBP5 but relatively strong when regulated by the nonphosphorylatable variant OsEBP89A–OsBP5. Therefore, OsSK41-mediated phosphorylation of OsEBP89 represents an additional layer of complexity in the regulation of amylose biosynthesis during rice grain development. In addition, our findings provide four possible sites for regulating rice grain AC via precise gene editing.

Key words: AP2/EREBP transcription factor, endosperm amylose content, GSK3-like family protein, MYC-like protein, OsSK41/OsGSK5, OsEBP89, OsBP5, rice grain

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