Transgenic expression of fungal accessory hemicellulases in Arabidopsis thaliana triggers transcriptional patterns related to biotic stress and defense response

• Published in: PloS one 2017-03, Vol.12 (3), p.e0173094-e0173094
• Main Authors: Tsai, Alex Yi-Lin, Chan, Kin, Ho, Chi-Yip, Canam, Thomas, Capron, Resmi, Master, Emma R, Bräutigam, Katharina
• Format: Article
• Language: English
• Subjects: Abundance; Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis thaliana; Arabinofuranosidase; Aspergillus nidulans; BASIC BIOLOGICAL SCIENCES; Biofuels; Biology; Biology and Life Sciences; Biomass; Biosynthesis; Botrytis cinerea; Cell walls; Cellulose; Chemical engineering; Ecology and Environmental Sciences; Enzymes; Esterase; Fungi; Gene expression; Genes; Genetic aspects; Genotypes; Glycoside Hydrolases - metabolism; Hemicellulases; Homeostasis; Host plants; Leaves; Lignin; Lignocellulose; Microorganisms; Next-generation sequencing; Phanerochaete; Photosynthesis; Plant cell walls; Plant extracts; Plant stress; Plant tissues; Plants (botany); Plants, Genetically Modified; Proteins; Renewable resources; Research and Analysis Methods; Salicylic acid; Signaling; Stress, Physiological; Sugar; Transcription; Transcription (Genetics); Transcription factors; Transcription, Genetic; Transcriptome; Transgenic plants; Xylan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0173094

The plant cell wall is an abundant and renewable resource for lignocellulosic applications such as the production of biofuel. Due to structural and compositional complexities, the plant cell wall is, however, recalcitrant to hydrolysis and extraction of platform sugars. A cell wall engineering strategy to reduce this recalcitrance makes use of microbial cell wall modifying enzymes that are expressed directly in plants themselves. Previously, we constructed transgenic Arabidopsis thaliana constitutively expressing the fungal hemicellulases: Phanerochaete carnosa glucurnoyl esterase (PcGCE) and Aspergillus nidulans α-arabinofuranosidase (AnAF54). While the PcGCE lines demonstrated improved xylan extractability, they also displayed chlorotic leaves leading to the hypothesis that expression of such enzymes in planta resulted in plant stress. The objective of this study is to investigate the impact of transgenic expression of the aforementioned microbial hemicellulases in planta on the host arabidopsis. More specifically, we investigated transcriptome profiles by short read high throughput sequencing (RNAseq) from developmentally distinct parts of the plant stem. When compared to non-transformed wild-type plants, a subset of genes was identified that showed differential transcript abundance in all transgenic lines and tissues investigated. Intriguingly, this core set of genes was significantly enriched for those involved in plant defense and biotic stress responses. While stress and defense-related genes showed increased transcript abundance in the transgenic plants regardless of tissue or genotype, genes involved in photosynthesis (light harvesting) were decreased in their transcript abundance potentially reflecting wide-spread effects of heterologous microbial transgene expression and the maintenance of plant homeostasis. Additionally, an increase in transcript abundance for genes involved in salicylic acid signaling further substantiates our finding that transgenic expression of microbial cell wall modifying enzymes induces transcriptome responses similar to those observed in defense responses.