Functional analysis of anS-adenosylhomocysteine hydrolase homolog of chestnut blight fungus

Abstract

S-adenosylhomocysteine (SAH), formed after donation of the methyl group of S-adenosylmethionine (SAM) to a methyl acceptor, is reversibly hydrolyzed to adenosine (ADO) and homocysteine (HCY) by S-adenosylhomocysteine hydrolase (SAHH). In chestnut blight fungus (Cryphonectria parasitica), sahh, a hypovirus-regulated gene that encodes a deduced SAHH protein was shown to have an SAHH enzymatic activity in vitro. Deletion of sahh resulted in the increased accumulation of intracellular SAH and SAM but decreased ADO, and a remarkably increased accumulation of transcripts that encode adenosine kinase, methionine adenosyltransferase, and an O-methyltransferase, key components of the methylation pathway. The Δsahh knockout mutants showed a phenotype of slower growth rate, fewer aerial hyphae, loss of orange pigment, absence of asexual fruiting bodies and conidia, and a significant reduction in virulence. Deletion of sahh significantly reduced the accumulation level of transcripts of the cyp1 that encodes cyclophilin A as well as genes of the heterotrimeric G-protein signaling pathways including cpga1, cpgb1, and cpgc1 and ste12, a target activated by the MAP kinase cascade. Taken together, we demonstrated that SAHH is required for virulence and multiple traits of phenotype in C. parasitica, by regulation of the expression of genes involved in key process of the cell.

Δ1-Pyrroline-5-Carboxylate/Glutamate Biogenesis Is Required for Fungal Virulence and Sporulation

“…Indeed, these pathways cover a large range of cell processes, from sensing environmental cues to the execution of cellular functions. In contrast, only a few downstream targets that execute an exact biochemical function have been reported [27], [37], [66], [67]. In this regard, the unveiling of viral perturbation of the proline/glutamate pathway in this work adds new knowledge to this colletion.…”

“…It is now known that the trimeric G protein signaling pathway [17]–[21], the inositol triphosphate (IP 3 )/Ca 2+ /calmodulin signaling pathway [22], and the mitogen-activated protein kinase (MAPK) signaling pathway are essential for C. parasitica virulence [23]–[26]. In addition to these pathways, genes functioning in the methylation pathway [27] and in apoptosis [28] were also found to be required for virulence.…”

Prb1, a subtilisin-like protease, is required for virulence and phenotypical traits in the chestnut blight fungus

“…Azocasein was diluted to 5 mg mL À1 in the buffer containing 25 mM Tris-HCl, 200 mM NaCl, and 25 mM CaCl 2 . Total protein extracts were prepared as described (Liao et al, 2012). Enzymatic assays were performed using total protein extracts or purified Prb1 protein with triplicate, and significance analysis was performed by t-test using SPSS software.…”

Involvement of Sulfur in the Biosynthesis of Essential Metabolites in Pathogenic Fungi of Animals, Particularly Aspergillus spp.: Molecular and Therapeutic Implications

“…Relevantly, SAH is a potent inhibitor of methylation (Caudill et al, 2001), and dissipation of SAH is important to avoid impaired cellular methylation, otherwise elevated SAH may impede mycelial growth. Consequently, SAM/SAH is considered a useful indicator of the cellular methylation potential, and perturbation of SAM/SAH has been studied through the disruption of S-adenosylhomocysteinase activity (Liao et al, 2012). As S-adenosylhomocysteinase catalyses the hydrolysis of SAH, any disruption to its activity would be expected to increase SAH levels, and reduce the SAM/SAH ratio.…”

“…The authors concluded that tobacco seeds were particularly sensitive to accurate SAM/SAH levels at critical developmental periods. In fungi, Liao et al (2012) investigated the effect of perturbed SAM/SAH in Cryphonectria parasitica. Deletion of the gene encoding S-adenosylhomocysteinase resulted in almost 10-fold increase in SAH abundance, and a twofold increase in SAM levels.…”