Differential Defense Responses of Upland and Lowland Switchgrass Cultivars to a Cereal Aphid Pest

Abstract

Yellow sugarcane aphid (YSA) (Sipha flava, Forbes) is a damaging pest on many grasses. Switchgrass (Panicum virgatum L.), a perennial C4 grass, has been selected as a bioenergy feedstock because of its perceived resilience to abiotic and biotic stresses. Aphid infestation on switchgrass has the potential to reduce the yields and biomass quantity. Here, the global defense response of switchgrass cultivars Summer and Kanlow to YSA feeding was analyzed by RNA-seq and metabolite analysis at 5, 10, and 15 days after infestation. Genes upregulated by infestation were more common in both cultivars compared to downregulated genes. In total, a higher number of differentially expressed genes (DEGs) were found in the YSA susceptible cultivar (Summer), and fewer DEGs were observed in the YSA resistant cultivar (Kanlow). Interestingly, no downregulated genes were found in common between each time point or between the two switchgrass cultivars. Gene co-expression analysis revealed upregulated genes in Kanlow were associated with functions such as flavonoid, oxidation-response to chemical, or wax composition. Downregulated genes for the cultivar Summer were found in co-expression modules with gene functions related to plant defense mechanisms or cell wall composition. Global analysis of defense networks of the two cultivars uncovered differential mechanisms associated with resistance or susceptibility of switchgrass in response to YSA infestation. Several gene co-expression modules and transcription factors correlated with these differential defense responses. Overall, the YSA-resistant Kanlow plants have an enhanced defense even under aphid uninfested conditions.

Dynamic Reconfiguration of Switchgrass Proteomes in Response to Rust (Puccinia novopanici) Infection

“…Proteomic studies using switchgrass are relatively limited [19][20][21][22][23] but can bolster more extensive evaluation of the physiological and genetic responses of this crop to pathogens that impact yield and quality. The proteomic data in this study broadly support earlier observations [6,13,[24][25][26][27][28][29][30] on the responses of Summer plants to biotic stressors while providing greater depth to the changes in cellular metabolism occurring in switchgrass in response to prolonged stress caused by Pn.…”

Activity of Cytosolic Ascorbate Peroxidase (APX) from Panicum virgatum against Ascorbate and Phenylpropanoids

“…PviAPX expression is induced during leaf senescence [ 57 ], and biotic stress [ 28 , 58 ]. Since biotic stress in switchgrass also activates other genes associated with phenylpropanoid metabolism and increases levels of defensive compounds synthesized from caffeic acid [ 28 , 58 , 59 ], it is plausible that PviAPX is involved in these processes along with its expected role in ROS homeostasis.…”

Temporal Regulation of Cold Transcriptional Response in Switchgrass

“…Computational approaches are powerful tools in the identification of genome-wide regulatory patterns in plants under biotic and abiotic stress conditions. In switchgrass, co-expression analysis has been used to establish the potential transcriptional regulatory networks in heat, drought, and biotic stress conditions (Hayford et al, 2022; Pingault et al, 2020). Recently, a comprehensive, transcriptomic study on several panicoid grasses, including switchgrass, revealed that machine learning approaches can be implemented to predict cold stress responses of genes within and between species based on nucleotide frequencies in promoter regions of genes, among other features (Meng et al, 2021).…”