A rice autophagy gene OsATG8b is involved in nitrogen remobilization and grain quality

Abstract Background: Enhancing nitrogen (N) use efficiency is a potential way of reducing excessive nitrogen application and increasing yield. Autophagy is a conservde degradation system in the evolution of eukaryotic cells and plays an important role in plant development and stress response. Autophagic cores are two conjugation pathways that attach ATG8 to PE and ATG5 to ATG12, which then help with vesicle elongation and enclosure. Rice has six ATG8 genes, which have not been functionally confirmed so far. Results: Autophagy activity of OsATG8b was confirmed 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 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. Conclusion: Autophagic role of OsATG8b was experimentally confirmed and OsATG8b-mediated autophagy is involved in N recycling to grains and contributes to the grain quality, indicating OsATG8b may be a potential gene for molecular breeding and cultivation of rice.