Pexophagy in Fungal Pathogenesis

tionally competent appressoria but are de- fective in their subsequent ability to form infectious hyphae (see figure). When inocu- lated directly into wounds, the atg26 mutant is able to grow in host tissue, confirming a specific defect in initial host invasion. Using GFP fused with the SKL peroxisomal targeting signal to monitor peroxisome syn- thesis and degradation, the authors show that both the wild-type and atg26 mutant strains produce numerous peroxisomes in conidia and appressoria a few hours after germina- tion, demonstrating normal peroxisome bio- genesis in the absence of the Atg26 protein. However, after 24 h, peroxisomes were de- graded in vacuoles of wild-type appressoria, while those of atg26 remained. No changes in mitochondrial numbers were observed in wild-type cells, suggesting that peroxisomes are preferentially degraded during the infec- tion process. The authors show that the both the phos- phoinositide binding domain and the catalytic domain of Atg26 are required for pexophagy and pathogenicity. Cellular localization experi- ments suggested that the phosphoinositide binding domain of Atg26 is required for the proper intracellular recruitment of Atg26 to membrane structures for pexophagy. They propose a model describing a potential link between peroxisome homeostasis and infection-related morphogenesis. Future stud- ies with these and related atg mutants should provide insight into the roles of organellar dynamics in cellular differentiation and path-