Abstract
Pexophagy, the degradation of peroxisomes via selective autophagy, depends on Atg20/Snx42 function in Saccharomyces cerevisiae. Besides its role in selective autophagy, Atg20/Snx42 is also involved in an autophagy-independent endosomal retrieval trafficking, in cooperation with two other sorting nexins, Snx41 and Snx4. Recently, we reported that the sorting nexin MoSnx41, which showed high sequence similarity to yeast Snx41 and Snx42/Atg20 proteins, regulates the gamma-glutamyl cycle and GSH production and is essential for conidiation and pathogenicity in Magnaporthe oryzae. Pexophagy was also found to be defective in Mosnx41Δ mutant. These findings indicate that MoSnx41 likely serves combined functions of Snx42/Atg20 and Snx41 in M. oryzae.. In this study, we performed complementation analyses and demonstrate that MoSnx41 alone serves the dual function of protein sorting (ScSnx41) and pexophagy (ScSnx42/Atg20). To study the potential biological function of pexophagy in fungal pathogenic life cycle, we created deletion mutants of potential pexophagy-specific genes, and characterized them in terms of pexophagy, conidiation and pathogenesis. We identified Pex14 as an essential protein for pexophagy in M. oryzae. Overall, our results show that pexophagy per se is not essential for asexual development or virulence in M. oryzae.
Highlights
Autophagy is a bulk degradation process conserved in all eukaryotes
When conidiation was induced in response to light, peroxisomes and autophagic vesicles were distinctly separate in conidiation-related structures, including the aerial hyphae (Figure 1A; middle panel; n=100; p < 0.05), the conidiophore and the conidia (Figure 1A; right panel; n=100; p < 0.05), indicating a likely lack of pexophagy or peroxisome turnover during M. oryzae conidiation
Peroxisomes were delivered to the vacuoles in non-germinating conidial cells during appressorium initiation or during invasive growth (Figure 1B, arrowheads), indicating that pexophagy likely occurs at these stages during pathogenesis in M. oryzae
Summary
Autophagy is a bulk degradation process conserved in all eukaryotes. Besides non-selective autophagy, there are several subtypes of selective autophagy, such as the Cvt pathway [1], mitophagy [2,3] and pexophagy [4,5].Peroxisomes are unit membrane-bound organelles, containing peroxidase and catalase activities and contribute to several lipid metabolic pathways and redox homeostasis in eukaryotic cells [6,7]. The M. oryzae genome contains a subset of ATG and PEX genes, whose orthologs in yeasts are dispensable for non-selective autophagy but serve as critical pexophagy regulators. Such specific ATG or PEX candidate genes are well-suited for studying the biological function of pexophagy in fungal pathogenesis. MoSnx is dispensable for non-selective autophagy, but essential for pexophagy, which is functionally similar to S. cerevisiae Snx42/Atg. MoSnx is dispensable for non-selective autophagy, but essential for pexophagy, which is functionally similar to S. cerevisiae Snx42/Atg20 It remains to be investigated whether pexophagy plays a role in M. oryzae conidiation and/or pathogenicity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
