Towards uncovering the roles of switchgrass peroxidases in plant processes

Abstract

Herbaceous perennial plants selected as potential biofuel feedstocks had been understudied at the genomic and functional genomic levels. Recent investments, primarily by the U.S. Department of Energy, have led to the development of a number of molecular resources for bioenergy grasses, such as the partially annotated genome for switchgrass (Panicum virgatum L.), and some related diploid species. In its current version, the switchgrass genome contains 65,878 gene models arising from the A and B genomes of this tetraploid grass. The availability of these gene sequences provides a framework to exploit transcriptomic data obtained from next-generation sequencing platforms to address questions of biological importance. One such question pertains to discovery of genes and proteins important for biotic and abiotic stress responses, and how these components might affect biomass quality and stress response in plants engineered for a specific end purpose. It can be expected that production of switchgrass on marginal lands will expose plants to diverse stresses, including herbivory by insects. Class III plant peroxidases have been implicated in many developmental responses such as lignification and in the adaptive responses of plants to insect feeding. Here, we have analyzed the class III peroxidases encoded by the switchgrass genome, and have mined available transcriptomic datasets to develop a first understanding of the expression profiles of the class III peroxidases in different plant tissues. Lastly, we have identified switchgrass peroxidases that appear to be orthologs of enzymes shown to play key roles in lignification and plant defense responses to hemipterans.

Identification of an orthologous clade of peroxidases that respond to feeding by greenbugs (Schizaphis graminum) in C4 grasses

“…Class III peroxidases have been implicated in many different aspects of plant defence, including the deposition of defence lignin and protection of the cell membrane against damage from ROS (Passardi et al 2005;Saathoff et al 2013) and the involvement of specific peroxidases in response to biotic stresses have been documented in several plant species Zamora et al 2009;Suzuki et al 2012). Over 100 peroxidase genes are encoded in the genomes of most grasses; however, readily distinguishing defence-related peroxidases from those involved in other metabolic pathways such as the biosynthesis of lignin or the detoxification of H 2 O 2 from chloroplasts or mitochondria, is not possible based simply on nucleotide or amino acid sequences.…”

“…These heme-containing enzymes can both produce and consume hydrogen peroxide (H 2 O 2 ), and are strongly upregulated in plants exposed to biotic and abiotic stress. The genomes of most plants contain in excess of 100 class III peroxidases that can be classified into several different subgroups (Passardi et al 2005;Saathoff et al 2013). Individual genes belonging to distinct subgroups can be differentially regulated in response to stress and other environmental cues (Passardi et al 2004a).…”

Induced resistance during the interaction pathogen x plant and the use of resistance inducers

“…The superoxide (O 2 .À ) can be produced in plants by many mechanisms including the activation of NADPH oxidase/synthases bound to the membrane, cell wall peroxidases, lipoxygenases, and as a result of electron transfer from mitochondria or chloroplasts. The O 2 .À usually oxidises organic molecules such as ascorbate or metals such as Fe 3+ (Saathoff et al, 2013;Thakur and Sohal, 2013 pathogens and is involved in cell wall strengthening and in the lignin biosynthesis process. It also acts as a second messenger, being responsible for the activation of the benzoic acid hydrolase, the enzyme responsible for the conversion of benzoic acid into salicylic acid.…”

O Papel Das Enzimas Antioxidantes Na Defesa Das Plantas Contra Insetos Herbívoros E Fitopatógenos

“…A atividade de peroxidase e/ou expressão de genes tem sido demonstrado que pode ser induzida por diferentes tipos de patógenos, incluindo fungos, bactérias e vírus (SASAKI et al, 2004;WANG et al, 2013;LAVANIA et al, 2006;HIRAGA et al, 2000;BABU et al, 2008). Estes estudos reforçam a hipótese que a classe III tem um importante papel na defesa de plantas e que pode servir como marcadores enzimáticos em resposta a estressores bióticos (SAATHOFF et al, 2013). HURA et al (2013) analisando a resposta bioquímica de plântulas de colza após inoculação de esporos do fungo Phoma lingam (Leptosphaeria maculans) observaram que houve aumento na atividade de peroxidase somente 72 horas após a inoculação e que este aumento ocorreu em resposta a alta produção de H 2 O 2 que ativou o sistema de defesa da planta, devido ao ataque do estressor biótico.…”