ATG genes encode proteins that are required for macroautophagy, the Cvt pathway 
and/or pexophagy. Using the published Atg protein sequences, we have screened 
protein and DNA databases to identify putative functional homologs (orthologs) 
in 21 fungal species (yeast and filamentous fungi) of which the genome sequences 
were available. For comparison with Atg proteins in higher eukaryotes, also an 
analysis of Arabidopsis thaliana and Homo sapiens databases was included. This 
analysis demonstrated that Atg proteins required for non-selective 
macroautophagy are conserved from yeast to man, stressing the importance of this 
process in cell survival and viability. The A. thaliana and human genomes encode 
multiple proteins highly similar to specific fungal Atg proteins (paralogs), 
possibly representing cell type-specific isoforms. The Atg proteins specifically 
involved in the Cvt pathway and/or pexophagy showed poor conservation, and were 
generally not present in A. thaliana and man. Furthermore, Atg19, the receptor 
of Cvt cargo, was only detected in Saccharomyces cerevisiae. Nevertheless, 
Atg11, a protein that links receptor-bound cargo (peroxisomes, the Cvt complex) 
to the autophagic machinery was identified in all yeast species and filamentous 
fungi under study. This suggests that in fungi an organism-specific form of 
selective autophagy may occur, for which specialized Atg proteins have evolved.