Transcriptome‐based analyses of phosphite‐mediated suppression of rust pathogens Puccinia emaculata and Phakopsora pachyrhizi and functional characterization of selected fungal target genes

Abstract

Phosphite (Phi) is used commercially to manage diseases mainly caused by oomycetes, primarily due to its low cost compared with other fungicides and its persistent control of oomycetous pathogens. We explored the use of Phi in controlling the fungal pathogens Puccinia emaculata and Phakopsora pachyrhizi, the causal agents of switchgrass rust and Asian soybean rust, respectively. Phi primes host defenses and efficiently inhibits the growth of P. emaculata, P. pachyrhizi and several other fungal pathogens tested. To understand these Phi-mediated effects, a detailed molecular analysis was undertaken in both the host and the pathogen. Transcriptomic studies in switchgrass revealed that Phi activates plant defense signaling as early as 1 h after application by increasing the expression of several cytoplasmic and membrane receptor-like kinases and defense-related genes within 24 h of application. Unlike in oomycetes, RNA sequencing of P. emaculata and P. pachyrhizi did not exhibit Phi-mediated retardation of cell wall biosynthesis. The genes with reduced expression in either or both rust fungi belonged to functional categories such as ribosomal protein, actin, RNA-dependent RNA polymerase, and aldehyde dehydrogenase. A few P. emaculata genes that had reduced expression upon Phi treatment were further characterized. Application of double-stranded RNAs specific to P. emaculata genes encoding glutamate N-acetyltransferase and cystathionine gamma-synthase to switchgrass leaves resulted in reduced disease severity upon P. emaculata inoculation, suggesting their role in pathogen survival and/or pathogenesis.

Comparative proteomics combined with analyses of transgenic plants reveal ZmREM1.3 mediates maize resistance to southern corn rust

“…Plant diseases caused by pathogens, such as viruses, bacteria and fungi, are responsible for major economic losses to agriculturally important crops worldwide (Kangasjarvi et al ., ). Rust pathogens are economically significant and difficult to manage because of their dynamic population structure, rapid evolution and wide dispersal of anemochorous spores (Gill et al ., ). P. polysora is a biotrophic fungal pathogen that causes SCR (Raid et al ., ).…”

Identification and Fine Mapping of RppM, a Southern Corn Rust Resistance Gene in Maize

“…With more than 7,000 species, rust fungi constitute the largest group of plant fungal pathogens and are difficult to control and manage because of their rapid evolution, dynamic population structure, and wide dispersal of anemochorous spores (Kangasjarvi et al, 2012;Rochi et al, 2016;Gill et al, 2018). Several of these pathogens are responsible for three rust diseases in maize: SCR, common rust, and tropical rust.…”

Transcriptome-Based Analysis of Phosphite-Induced Resistance against Pathogens in Rice

“…Some key genes in ethylene ( ERF1/2 ), jasmonic acid ( JAZ ), and salicylic acid ( TGA and PR1 ) pathways had higher expression levels in PHI-treated seedlings [ 28 ]. ACO1 was related to the JA/ET pathway [ 11 , 29 ]. The expression level of ACO1 was higher in PHI-treated seedlings than controls.…”

“…The expression of PR1 was promoted under PHI treatment. OPR1 belongs to the defense-related pathway [ 29 ]. PR1 and OPR1 expressions were significantly induced by PHI treatment.…”