Assessment and Optimization of Autophagy Monitoring Methods in Arabidopsis Roots Indicate Direct Fusion of

Autophagy is a degradation pathway that recycles cell materials upon encountering stress conditions or during specific developmental processes. To better understand the physiological roles of autophagy, proper monitoring methods are very important. In mammals and yeast, monitoring of autophagy is often performed with a green fluorescent protein (GFP)–ATG8 fusion protein or with acid-otropic dyes such as monodansylcadaverine (MDC) and LysoTracker Red (LTR). To evaluate these monitoring meth-ods, here we examined these systems by inducing autophagy in Arabidopsis thaliana roots as a model for monitoring autophagy in planta. Under carbon- and nitrogen-starved conditions, the number and size of vesicles labeled by GFP–ATG8 was increased for several hours and then grad-ually decreased to a level higher than that observed befor