PTS1 Peroxisomal Import Pathway Plays Shared and Distinct Roles to PTS2 Pathway in Development and Pathogenicity of Magnaporthe oryzae

Jiaoyu Wang,Yanli Wang,Ling Li,Rongyao Chai,Guochang Sun,Zhen Zhang,Xueqin Mao,Fucheng Lin,Haiping Qiu,Xinfa Du,Hua Jiang,Zhengguang Zhang

doi:10.1371/journal.pone.0055554

Abstract

Peroxisomes participate in various important metabolisms and are required in pathogenicity of fungal plant pathogens. Peroxisomal matrix proteins are imported from cytoplasm into peroxisomes through peroxisomal targeting signal 1 (PTS1) or peroxisomal targeting signal 2 (PTS2) import pathway. PEX5 and PEX7 genes participate in the two pathways respectively. The involvement of PEX7 mediated PTS2 import pathway in fungal pathogenicity has been documented, while that of PTS1 remains unclear. Through null mutant analysis of MoPEX5, the PEX5 homolog in Magnaporthe oryzae, we report the crucial roles of PTS1 pathway in the development and host infection in the rice blast fungus, and compared with those of PTS2. We found that MoPEX5 disruption specifically blocked the PTS1 pathway. Δmopex5 was unable to use lipids as sole carbon source and lost pathogenicity completely. Similar as Δmopex7, Δmopex5 exhibited significant reduction in lipid utilization and mobilization, appressorial turgor genesis and H2O2 resistance. Additionally, Δmopex5 presented some distinct defects which were undetected in Δmopex7 in vegetative growth, conidial morphogenesis, appressorial morphogenesis and melanization. The results indicated that the PTS1 peroxisomal import pathway, in addition to PTS2, is required for fungal development and pathogenicity of the rice blast fungus, and also, as a main peroxisomal import pathway, played a more predominant role than PTS2.

Highlights

Peroxisomes are single membrane-bound organelles present in almost all eukaryotes [1]
The cDNA amplicon showed that the open reading frame (ORF) of MoPEX5 was 2,044-bp long, contained 1 intron, and encoded a 650-aa peptide (MoPex5) which exhibited 57% aa identity to peroxin 5 of N. crassa (EAA36111) and 33% to that of S. cerevisiae (AAA64794) and contained four TPR domains (Figure 1A&B)
In view of the Dmopex7 mutant described from strain KJ201 [30], the Dmopex7 mutants from Guy11 were parallelly analyzed as a comparison with Dmopex5

Summary

Introduction

Peroxisomes are single membrane-bound organelles present in almost all eukaryotes [1]. These organelles contain more than 50 different enzymes involved in various metabolisms, such as fatty acid b-oxidation, glyoxylate cycle and degradation of reactive oxygen species (ROS) [2,3]. Peroxisomes do not have their own internal DNA molecules [7,8] Their matrix proteins and membrane proteins have to be encoded by nucleic genes, synthesized in cytoplasm and translocated to the organelle via post-translational transport [1]. PEX5 and PEX7 genes encode the receptors for PTS1 and PTS2 respectively, which bind the peroxisomal matrix proteins directly or indirectly via co-receptors [14,15]. The involvement of peroxisomes in host invasion of plant pathogenic fungi was demonstrated in several species [23,25,26,27]

Methods

Results

Conclusion