Abstract
Autophagy is an intracellular process for vacuolar degradation of cytoplasmic components. A recent genome-wide search revealed significant conservation among autophagy genes (ATGs) in yeasts and plants. It has not been proved, however, that Arabidopsis ATG genes are required for plant autophagy. To evaluate this requirement, we examined the ubiquitination-like Atg8 lipidation system. We generated transgenic Arabidopsis expressing a GFP-ATG8 fusion protein and established a system monitoring autophagy in whole plants. In wild-type plants, GFP-ATG8s were observed as ring shapes in the cytoplasm and were delivered to vacuolar lumens under nitrogen-starved conditions. By contrast, in T-DNA-insertion mutants of the ATGs (atgs), autophagosomes were not observed and the GFP-ATG8s were not delivered to the vacuole. The autophagy defective mutants exhibited early senescence phenotype and a reduction in the growth rate of roots. The physiological roles of plant autophagy will be discussed.
