Differential Regulation of Maize and Sorghum Orthologs in Response to the Fungal Pathogen Exserohilum turcicum

Abstract

Pathogens that infect more than one host offer an opportunity to study how resistance mechanisms have evolved across different species. Exserohilum turcicum infects both maize and sorghum and the isolates are host-specific, offering a unique system to examine both compatible and incompatible interactions. We conducted transcriptional analysis of maize and sorghum in response to maize-specific and sorghum-specific E. turcicum isolates and identified functionally related co-expressed modules. Maize had a more robust transcriptional response than sorghum. E. turcicum responsive genes were enriched in core orthologs in both crops, but only up to 16% of core orthologs showed conserved expression patterns. Most changes in gene expression for the core orthologs, including hub genes, were lineage specific, suggesting a role for regulatory divergent evolution. We identified several defense-related shared differentially expressed (DE) orthologs with conserved expression patterns between the two crops, suggesting a role for parallel evolution of those genes in both crops. Many of the differentially expressed genes (DEGs) during the incompatible interaction were related to quantitative disease resistance (QDR). This work offers insights into how different hosts with relatively recent divergence interact with a common pathogen. Our results are important for developing resistance to this critical pathogen and understanding the evolution of host-pathogen interactions.

Identification of quantitative trait loci for sorghum leaf blight resistance

“…Of particular interest is a wall‐associated kinase (Sobic.002G249600) on chromosome two that overlapped with the QTL in this study. Sobic.002G249600 was also differentially upregulated during the E. turcicum –sorghum interaction at 72 h (Adhikari et al., 2021). This is an interesting candidate gene for further study.…”

“…A genome‐wide association study (GWAS) utilizing the sorghum conversion panel identified 113 candidate genes associated with SLB resistance, including the sorghum ortholog of oxidative stress 3 and a glutathione S‐transferase encoding gene (Zhang et al., 2020). Differential gene expression analysis for the pathosystem indicated a diversity of genes involved in the sorghum– E. turcicum interaction, including genes implicated in pattern‐triggered immunity, quantitative disease resistance, and sugar transporters (Adhikari et al., 2021). There has been some work in maize examining mechanisms of resistance.…”

“…A recent study evaluating the phylogenetic relationship between maize, sorghum, and other grass species identified a cluster of NLRs conserved across several species conferring resistance to E. turcicum in sorghum (Martin et al., 2011). In a transcriptomics study comparing the E. turcicum response in maize and sorghum, core orthologs, or genes present in both maize and sorghum, were enriched in the set of genes that were expressed in both maize and sorghum after infection by E. turcicum , although only a fraction were differentially expressed in both crops (Adhikari et al., 2021). Further exploration of conserved resistance could provide insight into the evolution of this pathosystem.…”

Genome-wide screening of lectin putative genes from Sorghum bicolor L., distribution in QTLs and a probable implications of lectins in abiotic stress tolerance

“…The only paper published attempted to test the agglutination activity and blood specificity of sorghum whole grain crude extract [ 35 ]. However, several transcriptomic and expression analysis data that mentioned several sorghum lectins, as well as identified many lectin genes in QTLs of many traits are available [ 14 , 16 , 66 , 67 ]. The statistically significant overrepresentation and clustering of sorghum’s lectin putative genes in QTLs related to many traits associated with drought, cold, composition, and morphology highlights the importance of such proteins, and predominantly associates them with plant developmental and growth aspects as well environmental adaptation.…”

Advances in molecular plant pathology, plant abiotic and biotic stress

“…A mixture of isolates was used to best reproduce disease pressure observed in 2019. For the 2020 greenhouse experiment, plants were inoculated with a spore suspension at the V3 stage (Adhikari et al, 2021). Fungal isolates were grown on lactose-casein hydrolysate agar (LCA) media for 14 days under 12/12 hr light/dark photoperiod at room temperature.…”