FpPEX5 and FpPEX7 are involved in the growth, reproduction, DON toxin production, and pathogenicity in Fusarium pseudograminearum.

Fusarium crown rot, caused by Fusarium pseudograminearum, is a devastating disease affecting the yield and quality of cereal crops. Peroxisomes are single-membrane organelles that play a critical role in various biological processes in eukaryotic cells. To functionally characterise peroxisome biosynthetic receptor proteins FpPEX5 and FpPEX7 in F. pseudograminearum, we constructed deletion mutants, ΔFpPEX5 and ΔFpPEX7, and complementary strains, ΔFpPEX5-C and ΔFpPEX7-C, and analysed the functions of FpPEX5 and FpPEX7 proteins using various phenotypic observations. The deletion of FpPEX5 and FpPEX7 resulted in a significant deficiency in mycelial growth and conidiation and blocked the peroxisomal targeting signal 1 and peroxisomal targeting signal 2 pathways, which are involved in peroxisomal matrix protein transport, increasing the accumulation of lipid droplets and reactive oxygen species. The deletion of FpPEX5 and FpPEX7 may reduce the formation of toxigenic bodies and decrease the pathogenicity of F. pseudograminearum. These results indicate that FpPEX5 and FpPEX7 play vital roles in the growth, asexual reproduction, virulence, and fatty acid utilisation of F. pseudograminearum. This study provides a theoretical basis for controlling stem rot in wheat.

Regulatory Mechanism of Peroxisome Number Reduction Caused by FgPex4 and FgPex22-like Deletion in Fusarium graminearum.

Peroxisomes are single-membrane-bound organelles that play critical roles in eukaryotic cellular functions. Peroxisome quantity is a key factor influencing the homeostasis and pathogenic processes of pathogenic fungi. The aim of the present study was to investigate the underlying mechanisms of the reduction in number of peroxisomes in Fusarium graminearum consequent to FgPex4 and FgPex22-like deletion. The number of peroxisomes decreased by 40.55% and 39.70% when FgPex4 and FgPex22-like, respectively, were absent. Peroxisome biogenesis-related proteins, as well as inheritance- and division-related dynamin-like proteins were reduced at the transcriptional level in the mutant strains. In addition, the degree of pexophagy was intensified and the accumulation of ubiquitinated FgPex5 was also increased in F. graminearum when FgPex4 or FgPex22-like was absent. The findings suggest that FgPex4 and FgPex22-like influence the number of peroxisomes by influencing peroxisome biogenesis and pexophagy.