Abstract
Autophagy is an intracellular degradation process that facilitates material recycling to maintain cellular homeostasis in eukaryotes. Atg2 is a phospholipid transfer protein involved in cellular autophagy in Saccharomyces cerevisiae. To date, the role of Atg2 in growth, development and pathogenicity of the gray mold fungus Botrytis cinerea remains unknown. In this study, we identified and characterized an Atg2 ortholog, designated as BcAtg2, in B. cinerea. Deletion of BcATG2 resulted in a block of the autophagic process in B. cinerea. The ΔBcAtg2 mutant failed to produce sclerotia, and showed significant reduction in mycelial growth rate, formation of aerial mycelium and conidiation. In addition, the ΔBcAtg2 mutant lost the ability to form infection structures and cause symptom on host plants. All of these phenotypic changes in ΔBcAtg2 mutant were restored by targeted gene complementation. Moreover, BcAtg2 was demonstrated to physically interact with the phosphoinositide binding protein BcAtg18. Taken together, these results indicate that BcAtg2 plays an important role in vegetative growth, development and pathogenicity in B. cinerea.
Highlights
Botrytis cinerea is a filamentous fungal pathogen that causes gray mold on a wide range of hosts, including fruits, vegetables and ornamental flowers (Fillinger and Elad 2016)
Protein domain architectures were characterized by using the Simple Modular Architecture Research Tool (SMART), and the results showed that BcAtg2
Under nitrogen-starvation conditions, the autophagic bodies were observed in the vacuole of the wild-type strain B05.10, whereas no autophagic bodies were observed in the vacuole of the BcATG2 deletion mutant ΔBcAtg2 (Fig. 3a)
Summary
Botrytis cinerea (teleomorph Botryotinia fuckeliana) is a filamentous fungal pathogen that causes gray mold on a wide range of hosts (more than 500 plant species), including fruits, vegetables and ornamental flowers (Fillinger and Elad 2016). Autophagy is an evolutionarily conserved intracellular degradation process in eukaryotes, which plays an important role in the maintenance of cellular homeostasis (Yorimitsu and Klionsky 2005). The process of autophagy includes sequestration of bulky cytosolic contents such as long-lived proteins and damaged organelles into vesicular compartments, followed by delivery of these intracellular materials to lysosomes/vacuoles for degradation (Mizushima 2007). A central event in autophagy is the biogenesis of double-membrane vesicles termed autophagosomes, which sequester intracellular components for degradation in lysosomes/vacuoles (Xie and Klionsky 2007). Previous studies in yeast and mammals have shown that the autophagy-related protein Atg forms a complex with the phosphatidylinositol 3-phosphate (PI3P)-binding protein Atg to initiate autophagosome biogenesis in the preautophagosomal structure
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