Family-Four Aldehyde Dehydrogenases Play an Indispensable Role in the Pathogenesis of Magnaporthe oryzae

Abstract

The oxidative degradation of lipids through lipid peroxidation processes results in the generation of free fatty acid radicals. These free radicals including reactive oxygen species (ROS) serve as a substrate for generating reactive aldehydes. The accumulation of free fatty acid radicals, ROS, and reactive aldehydes in cell compartments beyond physiological threshold levels tends to exert a damaging effect on proximal membranes and distal tissues. Living organisms deploy a wide array of efficient enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and aldehyde dehydrogenases (ALDHs) for scavenging reactive molecules and intermediates produced from membrane lipid peroxidation events. Although the contributions of SOD, CAT, and POD to the pathogenesis of microbial plant pathogens are well known, the influence of ALDH genes on the morphological and infectious development of plant pathogenic microbes is not well understood. In this study, we deployed RNA interference (RNAi) techniques and successfully silenced two putative family-four aldehyde dehydrogenase genes potassium-activated aldehyde dehydrogenase (MoKDCDH) and delta-1-pyrrorine-5-carboxylate dehydrogenase (MoP5CDH) in the rice blast pathogen Magnaporthe oryzae. The results obtained from the phenotypic analysis of individual knock-down strains showed that the RNAi-mediated inactivation of MoKDCDH and MoP5CDH triggered a significant reduction in conidiogenesis and vegetative growth of ΔMokdcdh and ΔMop5cdh strains. We further observed that downregulating the expression of MoKDCDH and MoP5CDH severely compromised the pathogenesis of the rice blast fungus. Also, the disruption of MoKDCDH and MoP5CDH M. oryzae undermined membrane integrity and rendered the mutant strains highly sensitive to membrane stress inducing osmolytes. However, the MoKDCDH and MoP5CDH knock-down strains generated in this study displayed unaltered cell wall integrity and thus suggested that family-four ALDHs play a dispensable role in enforcing cell wall-directed stress tolerance in M. oryzae. From these results, we deduced that family-four ALDHs play a conserved role in fostering membrane integrity in M. oryzae possibly by scavenging reactive aldehydes, fatty acid radicals, and other alcohol derivatives. The observation that downregulating the expression activities of MoKDCDH had a lethal effect on potential mutants further emphasized the need for comprehensive and holistic evaluation of the numerous ALDHs amassed by the rice blast fungus for their possible engagement as suitable targets as antiblast agents.

Interactome of Glyceraldehyde-3-Phosphate Dehydrogenase Points to the Existence of Metabolons in Paracoccidioides lutzii

“…Through the activity of ALDH, pathogens evade osmotic, oxidative and other cellular stressors besides host immune response (Singh et al, 2004). The interaction between GAPDH and ALDH may optimize host invasion and protection against stress conditions (Abdul et al, 2018).…”

Translation Initiation Factor eIF4E Positively Modulates Conidiogenesis, Appressorium Formation, Host Invasion and Stress Homeostasis in the Filamentous Fungi Magnaporthe oryzae

“…For transformation, protoplasts were prepared following standard protocols (Abdul et al, 2018). The wild type strain was first cultured in liquid CM medium and placed in a 28 • C shaker for 3-4 days at 110 rpm, and after that, the media was drained off, and the cultured colonies were ground using mortar and pestle, then resuspended in fresh liquid CM and incubated for 12-14 h in a 28 • C shaker at 130 rpm.…”

Recent Development on Plant Aldehyde Dehydrogenase Enzymes and Their Functions in Plant Development and Stress Signaling

“…However, it is worth noticing the recent observations that downregulating the expression of some ALDH genes in plant pathogens negatively impacted their virulence. For example, the silencing of two putative family-four aldehyde dehydrogenase genes potassium-activated aldehyde dehydrogenase ( MoKDCDH ) and delta-1-pyrrorine-5-carboxylate dehydrogenase ( MoP5CDH ) in the rice blast pathogen Magnaporthe oryzae significantly compromised the pathogenesis of the fungus [ 139 ]. The silencing of MoKDCDH appeared sublethal in the mutants, thereby offering the possibility to target this enzyme for selective inhibition, since most plants do not express ALDH4 family proteins.…”