Biological Role of Trichoderma harzianum-Derived Platelet-Activating Factor Acetylhydrolase (PAF-AH) on Stress Response and Antagonism

Abstract

We investigated the properties of platelet-activating factor acetylhydrolase (PAF-AH) derived from Trichoderma harzianum. The enzyme, comprised of 572 amino acids, shares high homology with PAF-AH proteins from T. koningii and other microbial species. The optimum enzymatic activity of PAF-AH occurred at pH 6 in the absence of Ca2+ and it localized in the cytoplasm, and we observed the upregulation of PAF-AH expression in response to carbon starvation and strong heat shock. Furthermore, PAF-AH knockout transformant growth occurred more slowly than wild type cells and over-expression strains grown in SM medium at 37°C and 42°C. In addition, PAF-AH expression significantly increased under a series of maize root induction assay. Eicosanoic acid and ergosterol levels decreased in the PAF-AH knockouts compared to wild type cells, as revealed by GC/MS analysis. We also determined stress responses mediated by PAF-AH were related to proteins HEX1, Cu/Zn superoxide dismutase, and cytochrome c. Finally, PAF-AH exhibited antagonistic activity against Rhizoctonia solani in plate confrontation assays. Our results indicate PAF-AH may play an important role in T. harzianum stress response and antagonism under diverse environmental conditions.

The putative phospholipase Lip2 counteracts oxidative damage and influences the virulence of Ustilago maydis

“…The three genes predicted to encode putative PLAs (um00133, um01927 and um01017) were of particular interest, given the role of PLA 2 enzymes in resistance to oxidative stress in other organisms (Foulks et al ., ; Yu et al ., ). Domain analysis for the three candidate PLA 2 enzymes identified a patatin/PLA 2 ‐related domain (IPR002641) in the gene um01017.…”

“…We hypothesized that the virulence defect in Δlip2 mutants was caused by their increased susceptibility to oxidative stress, perhaps generated as part of the early plant defence response to infection. This would be consistent with the role of PAFAHs in the response to oxidative stress in fungi and other organisms (Foulks et al ., ; Rosenson and Stafforini, ; Yazawa et al ., ; Yu et al ., ). We therefore assessed the susceptibilities of the Δlip1 and Δlip2 mutants to oxidative stress caused by H 2 O 2 .…”

“…The increased susceptibility of the lip2 deletion mutant to H 2 O 2 is consistent with known roles for PLA 2 enzymes in other organisms (Foulks et al ., ; Yu et al ., ), and this observation prompted a more detailed examination of the source of the oxidative stress. However, the mutants did not show altered susceptibility to other sources of oxidative stress, including CuSO 4 and tert ‐butyl hydroperoxide (data not shown).…”

“…The PL encoded by a homologue of plg7 in Trichoderma harzianum is also a stress‐responsive protein. Deletion mutants for the gene in T. harzianum exhibit slow growth, sensitivity to oxidative stress caused by hydrogen peroxide (H 2 O 2 ) and decreased levels of eicosanoids and ergosterol (Yu et al ., ). The ability to deal with oxidative stress caused by reactive oxygen species (ROS) is an important attribute of a successful plant pathogen because the oxidative burst is an early plant defence response.…”

The platelet-activating factor acetylhydrolase gene derived fromTrichoderma harzianuminduces maize resistance toCurvularia lunatathrough the jasmonic acid signaling pathway

“…Wild-type (WT) T. harzianum T28 (CCTCC AF 2013026) and the KO40 transformant (PAF-AH disruption transformant) were described by Yu et al [13] The T28, KO40, and over-expression (OE) transformants were cultivated on PDA medium (Difco, Becton Dickinson & Co., Franklin Lakes, NJ, USA) at 28 C until sporulation (6 days). The conidia of C. lunata (CCTCC AF 2013027) were inoculated onto maize leaves to test Trichoderma-induced systemic resistance.…”