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Transcriptomics of induced defense responses to Greenbug aphid feeding in near isogenic wheat lines

ABSTRACT: The greenbug aphid, Schizaphis graminum (Rondani) is an important cereal pest periodically threatening wheat yields in the United States and around the world. The wheat breeding program at Texas A&M University has introgressed the greenbug resistance gene Gb3 from synthetic wheat ‘Largo’ into the widely grown cultivars TAM 110 and TAM 112; however, the molecular mechanisms of Gb3-induced defense responses remain unknown. Using Affymetrix GeneChip Wheat Genome Arrays, we investigated the temporal dynamics of Gb3-mediated transcriptional responses upon greenbug feeding on resistant and susceptible bulks (RB and SB respectively) derived from two near-isogenic lines. Following statistical analysis, the MapMan functional classification on 692 differentially expressed transcripts from the interaction group identified 122 transcripts that were putatively associated with biotic stress responses. In RB, Gb3 induced transmembrane receptor kinases and downstream early defense signal transduction pathways. However, non-Gb3 mediated pathways in SB prompted induction of transcripts mediating callose decomposition and transcripts regulating biosynthesis of stress hormones jasmonic acid, ethylene, and abscisic acid. Additionally, the SB showed elevated levels of transcripts mediating redox homeostasis, peroxidases, glutathione S-transferases, and defense-related secondary metabolites. Overall, the results indicated that greenbugs inflicted more damage in the SB compared to RB and absence of Gb3-mediated signaling resulted in cell wall remodeling and strong accumulation of toxic compounds warranting production of antioxidant and defense-related compounds. The study reinforced our knowledge about preferential feeding on S genotypes and plausible antixenosis or tolerance-related defense signaling in Gb3-associated R genotypes and generated several new hypotheses.

ORGANISM(S): Triticum aestivum

PROVIDER: GSE45995 | GEO | 2022/01/01

REPOSITORIES: GEO

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Project description:Water soluble carbohydrates (WSC, composed of mainly fructans, sucrose, glucose and fructose) deposited in wheat stems are important carbon sources for grain filling. Variation in stem WSC concentrations among wheat genotypes is one of the genetic factors influencing grain weight and yield under water-limited environments. Here, we describe the molecular dissection of carbohydrate metabolism in stems, at the WSC accumulation phase, of recombinant inbred SB (Seri/Babax) lines of Triticum aestivum differing in stem WSC concentrations. Affymetrix GeneChip analysis of carbohydrate metabolic enzymes revealed that the mRNA levels of two fructan synthetic enzyme families (sucrose:sucrose 1-fructosyltransferase and sucrose:fructan 6-fructosyltransferase) in the stem were positively correlated with stem WSC and fructan concentrations, while the mRNA levels of enzyme families involved in sucrose hydrolysis (sucrose synthase and soluble acid invertase) were inversely correlated with WSC concentrations. Differential regulation of the mRNA levels of these sucrose hydrolytic enzymes in SB lines resulted in genotypic differences in these enzyme activities. Down-regulation of sucrose synthase and soluble acid invertase in high WSC lines was accompanied by significant decreases in the mRNA levels of enzyme families related to sugar catabolic pathways (fructokinase and mitochondrion pyruvate dehydrogenase complex) and enzyme families involved in diverting UDP-glucose to cell wall synthesis (UDP-glucose 6-dehydrogenase, UDP-glucuronate decarboxylase and cellulose synthase), resulting in a reduction in cell wall polysaccharide contents (mainly hemicellulose) in the stem of high WSC lines. These data suggest that differential carbon partitioning in the wheat stem is one mechanism that contributes to genotypic variation in WSC accumulation. We used Affymetrix GeneChip to dissect genotypic variation in carbohydrate metabolism related to water soluble carbohydrate accumulation in stems of wheat. Experiment Overall Design: 8 genotypes of recombinant inbred lines Seri M82 x Babax with 2 biological replicates per genotype. Grown in the field under rain-fed conditions

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Transcriptomics of induced defense responses to Greenbug aphid feeding in near isogenic wheat lines

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