Autophagy-Related Gene PlATG6a Is Involved in Mycelial Growth, Asexual Reproduction and Tolerance to Salt and Oxidative Stresses in Peronophythora&nbsp;litchii.

Jingrui Wang,Wen Li,Weixiong Huang,Liuchen Liu,Pinggen Xi,Zide Jiang,Guanghui Kong,Gangqiang Zhou,Dinan Feng

doi:10.3390/ijms23031839

Autophagy-Related Gene PlATG6a Is Involved in Mycelial Growth, Asexual Reproduction and Tolerance to Salt and Oxidative Stresses in Peronophythora litchii.

Jingrui Wang, Wen Li + Show 7 more

Open Access

https://doi.org/10.3390/ijms23031839

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Abstract

Autophagy is ubiquitously present in eukaryotes. During this process, intracellular proteins and some waste organelles are transported into lysosomes or vacuoles for degradation, which can be reused by the cell to guarantee normal cellular metabolism. However, the function of autophagy-related (ATG) proteins in oomycetes is rarely known. In this study, we identified an autophagy-related gene, PlATG6a, encoding a 514-amino-acid protein in Peronophythora litchii, which is the most destructive pathogen of litchi. The transcriptional level of PlATG6a was relatively higher in mycelium, sporangia, zoospores and cysts. We generated PlATG6a knockout mutants using CRISPR/Cas9 technology. The P. litchii Δplatg6a mutants were significantly impaired in autophagy and vegetative growth. We further found that the Δplatg6a mutants displayed decreased branches of sporangiophore, leading to impaired sporangium production. PlATG6a is also involved in resistance to oxidative and salt stresses, but not in sexual reproduction. The transcription of peroxidase-encoding genes was down-regulated in Δplatg6a mutants, which is likely responsible for hypersensitivity to oxidative stress. Compared with the wild-type strain, the Δplatg6a mutants showed reduced virulence when inoculated on the litchi leaves using mycelia plugs. Overall, these results suggest a critical role for PlATG6a in autophagy, vegetative growth, sporangium production, sporangiophore development, zoospore release, pathogenesis and tolerance to salt and oxidative stresses in P. litchii.

Highlights

Oomycetes are a class of ubiquitous filamentous eukaryotic microorganisms, which are evolutionarily close to photosynthetic algae [1]
PlATG6a and Its Orthologs Are Widespread in Oomycetes, and PlATG6 Is Up-Regulated in Zoospores and Cysts in Peronophythora litchii
Orthologs of PlATG6a could be found in all these species (Supplementary Table S2), indicating that PlATG6a orthologs are widespread in oomycetes (Figure 1A)

Summary

Introduction

Oomycetes are a class of ubiquitous filamentous eukaryotic microorganisms, which are evolutionarily close to photosynthetic algae [1]. Many oomycetes are economically significant pathogens affecting agriculture, forestry and the ecosystem. Phytophthora infestans, P. sojae, P. capsici and Peronophythora litchii severely damage potato, soybean, cucurbits, and litchi, respectively [2,3]. The molecular mechanisms of P. litchii growth, development and pathogenesis are largely unknown [4]. Recent studies have revealed a wide variety of physiological roles for autophagy involved in pathogens and plants [8]. In many eukaryotic plant pathogens, such as Magnaporthe oryzae, P. sojae, Ustilago maydis and Fusarium graminearum, autophagy is associated with sporulation, virulence and development [9,10,11,12,13,14,15,16]

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