A Rice Autophagy Gene OsATG8b Is Involved in Nitrogen Remobilization and Control of Grain Quality

Tian Fan; Wu Yang; Xuan Zeng; Xinlan Xu; Yanling Xu; Xiaorong Fan; Ming Luo; Changen Tian; Kuaifei Xia; Mingyong Zhang

doi:10.3389/fpls.2020.00588

A Rice Autophagy Gene OsATG8b Is Involved in Nitrogen Remobilization and Control of Grain Quality

Front Plant Sci. 2020 Jun 4:11:588. doi: 10.3389/fpls.2020.00588. eCollection 2020.

Authors

Tian Fan^{1

2}, Wu Yang², Xuan Zeng², Xinlan Xu², Yanling Xu³, Xiaorong Fan³, Ming Luo², Changen Tian¹, Kuaifei Xia^{2

4}, Mingyong Zhang^{2

4}

Affiliations

¹ School of Life Sciences, Guangzhou University, Guangzhou, China.
² Innovation Academy for Seed Design, Guangdong Provincial Key Laboratory of Applied Botany, Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
³ State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, China.
⁴ Center of Economic Botany, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China.

Abstract

Enhancing nitrogen (N) use efficiency is a potential way to reduce excessive nitrogen application and increase yield. Autophagy is a conserved degradation system in the evolution of eukaryotic cells and plays an important role in plant development and stress response. Autophagic cores have two conjugation pathways that attach the product of autophagy-related gene 8 (ATG8) to phosphatidylethanolamine (PE) and ATG5 to ATG12, respectively, which then help with vesicle elongation and enclosure. Rice has six ATG8 genes, which have not been functionally confirmed so far. We identified the rice gene OsATG8b and characterized its role in N remobilization to affect grain quality by generating transgenic plants with its over-expression and knockdown. Our study confirmed the autophagy activity of OsATG8b through the complementation of the yeast autophagy-defective mutant scatg8 and by observation of autophagosome formation in rice. The autophagy activity is higher in OsATG8b-OE lines and lower in OsATG8b-RNAi than that in wild type (ZH11). ¹⁵N pulse-chase analysis revealed that OsATG8b-OE plants conferred higher N recycling efficiency to grains, while OsATG8b-RNAi transgenic plants exhibited lower N recycling efficiency and poorer grain quality. The autophagic role of OsATG8b was experimentally confirmed, and it was concluded that OsATG8b-mediated autophagy is involved in N recycling to grains and contributes to the grain quality, indicating that OsATG8b may be a potential gene for molecular breeding and cultivation of rice.

Keywords: OsATG8b; autophagy; nitrogen recycling; rice; seed quality.