Eukaryotic cells have the ability to degrade proteins and organelles by 
selective and nonselective modes of micro- and macroautophagy. In addition, 
there exist both constitutive and regulated forms of autophagy. For example, 
pexophagy is a selective process for the regulated degradation of peroxisomes by 
autophagy. Our studies have shown that the differing pathways of autophagy have 
many molecular events in common. In this article, we have identified a new 
member in the family of autophagy genes. GSA12 in Pichia pastoris and its 
Saccharomyces cerevisiae counterpart, CVT18, encode a soluble protein with two 
WD40 domains. We have shown that these proteins are required for pexophagy and 
autophagy in P. pastoris and the Cvt pathway, autophagy, and pexophagy in S. 
cerevisiae. In P. pastoris, Gsa12 appears to be required for an early event in 
pexophagy. That is, the involution of the vacuole or extension of vacuole arms 
to engulf the peroxisomes does not occur in the gsa12 mutant. Consistent with 
its role in vacuole engulfment, we have found that this cytosolic protein is 
also localized to the vacuole surface. Similarly, Cvt18 displays a subcellular 
localization that distinguishes it from the characterized proteins required for 
cytoplasm-to-vacuole delivery pathways.