Atg21p is essential for macropexophagy and microautophagy in the yeastHansenula polymorpha

Abstract
ATG genes are required for autophagy‐related processes that transport proteins/organelles destined for proteolytic degradation to the vacuole. Here, we describe the identification and characterisation of the Hansenula polymorpha ATG21 gene. Its gene product Hp‐Atg21p, fused to eGFP, had a dual location in the cytosol and in peri‐vacuolar dots. We demonstrate that Hp‐Atg21p is essential for two separate modes of peroxisome degradation, namely glucose‐induced macropexophagy and nitrogen limitation‐induced microautophagy. In atg21 cells subjected to macropexophagy conditions, sequestration of peroxisomes tagged for degradation is initiated but fails to complete.