AUTHOR=Abdul Waheed , Aliyu Sami R. , Lin Lili , Sekete Malota , Chen Xiaomin , Otieno Frankline J. , Yang Tao , Lin Yahong , Norvienyeku Justice , Wang Zonghua 

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

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00980

DOI=10.3389/fpls.2018.00980

ISSN=1664-462X

ABSTRACT=<p>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 (<italic>SOD</italic>), catalase (<italic>CAT</italic>), peroxidase (<italic>POD</italic>), and aldehyde dehydrogenases (<italic>ALDHs</italic>) for scavenging reactive molecules and intermediates produced from membrane lipid peroxidation events. Although the contributions of <italic>SOD</italic>, <italic>CAT</italic>, and <italic>POD</italic> to the pathogenesis of microbial plant pathogens are well known, the influence of <italic>ALDH</italic> 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 (<italic>MoKDCDH</italic>) and delta-1-pyrrorine-5-carboxylate dehydrogenase (<italic>MoP5CDH</italic>) in the rice blast pathogen <italic>Magnaporthe oryzae</italic>. The results obtained from the phenotypic analysis of individual knock-down strains showed that the RNAi-mediated inactivation of <italic>MoKDCDH</italic> and <italic>MoP5CDH</italic> triggered a significant reduction in conidiogenesis and vegetative growth of Δ<italic>Mokdcdh</italic> and Δ<italic>Mop5cdh</italic> strains. We further observed that downregulating the expression of <italic>MoKDCDH</italic> and <italic>MoP5CDH</italic> severely compromised the pathogenesis of the rice blast fungus. Also, the disruption of <italic>MoKDCDH</italic> and <italic>MoP5CDH M. oryzae</italic> undermined membrane integrity and rendered the mutant strains highly sensitive to membrane stress inducing osmolytes. However, the <italic>MoKDCDH</italic> and <italic>MoP5CDH</italic> knock-down strains generated in this study displayed unaltered cell wall integrity and thus suggested that family-four <italic>ALDH</italic>s play a dispensable role in enforcing cell wall-directed stress tolerance in <italic>M. oryzae</italic>. From these results, we deduced that family-four <italic>ALDH</italic>s play a conserved role in fostering membrane integrity in <italic>M. oryzae</italic> possibly by scavenging reactive aldehydes, fatty acid radicals, and other alcohol derivatives. The observation that downregulating the expression activities of <italic>MoKDCDH</italic> had a lethal effect on potential mutants further emphasized the need for comprehensive and holistic evaluation of the numerous <italic>ALDH</italic>s amassed by the rice blast fungus for their possible engagement as suitable targets as antiblast agents.</p>