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

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 genes, which have not been functionally confirmed so far. We identified the rice gene 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 and by observation of autophagosome formation in rice. The autophagy activity is higher in -OE lines and lower in -RNAi than that in wild type (ZH11). N pulse-chase analysis revealed that -OE plants conferred higher N recycling efficiency to grains, while -RNAi transgenic plants exhibited lower N recycling efficiency and poorer grain quality. The autophagic role of 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.