The Mitogen-Activated Protein Kinase PlMAPK2 Is Involved in Zoosporogenesis and Pathogenicity of Peronophythoralitchii.

Jiamin Huang,Minhui Li,Guanghui Kong,Tianfang Guan,Wensheng Yang,Junjian Situ,Yizhen Deng,Liqun Jiang,Wen Li,Qingqing Zhao,Zide Jiang,Jingrui Wang,Weixiong Huang,Pinggen Xi

doi:10.3390/ijms22073524

Jiamin Huang, Minhui Li + Show 12 more

Open Access

https://doi.org/10.3390/ijms22073524

Copy DOI

Abstract

As an evolutionarily conserved pathway, mitogen-activated protein kinase (MAPK) cascades function as the key signal transducers that convey information by protein phosphorylation. Here we identified PlMAPK2 as one of 14 predicted MAPKs encoding genes in the plant pathogenic oomycete Peronophythora litchii. PlMAPK2 is conserved in P. litchii and Phytophthora species. We found that PlMAPK2 was up-regulated in sporangium, zoospore, cyst, cyst germination and early stage of infection. We generated PlMAPK2 knockout mutants using the CRISPR/Cas9 method. Compared with wild-type strain, the PlMAPK2 mutants showed no significant difference in vegetative growth, oospore production and sensitivity to various abiotic stresses. However, the sporangium release was severely impaired. We further found that the cleavage of the cytoplasm into uninucleate zoospores was disrupted in the PlMAPK2 mutants, and this developmental phenotype was accompanied by reduction in the transcription levels of PlMAD1 and PlMYB1 genes. Meanwhile, the PlMAPK2 mutants exhibited lower laccase activity and reduced virulence to lychee leaves. Overall, this study identified a MAPK that is critical for zoosporogenesis by regulating the sporangial cleavage and pathogenicity of P. litchii, likely by regulating laccase activity.

Highlights

Oomycetes are fungus-like eukaryotic microorganisms which are evolutionarily close to photosynthetic algae, but are distant from fungi [1,2]
We characterized the functions of P. litchii mitogen-activated protein kinase, PlMAPK2
The PlMAPK2 mutants were exposed to various stresses, and we found that PlMAPK2 mutants showed no significance in responses to various stresses comparing with WT (Figure 8)

Summary

Introduction

Oomycetes are fungus-like eukaryotic microorganisms which are evolutionarily close to photosynthetic algae, but are distant from fungi [1,2]. Phytophthora infestans, Phytophthora capsici, Phytophthora sojae and Peronophythora litchii severely damage potato, soybean, cucurbits and lychee, respectively [3,4]. Lychee downy blight caused by P. litchii is the most destructive disease of lychee and results in crop losses ranging from 30% to 80% annually [5]. As evolutionarily conserved signaling pathways, mitogen-activated protein kinase (MAPK) cascades function as key signal transducers in plants, animals, fungi and oomycetes, which utilize protein phosphorylation/dephosphorylation cycles to channel information [6]. Activated MAPKs can phosphorylate downstream substrates, regulating their functions [6]

Methods

Results

Conclusion