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Guevara Rozo, Sydne

University of British Columbia

Lignocellulosic feedstocks are pivotal to the transition to a biobased economy, however, the plant cell wall evolved to withstand stresses, microbial attack, and degradation, and therefore presents significant challenges for industrial biomass processing. Structural modifications of xylan, the major hemicellulose in angiosperms, have been shown to positively affect cell wall deconstruction by interfering with xylan-cellulose-lignin interactions. In contrast, the role of mannan, a major hemicellulose commonly found in gymnosperms (minor hemicellulose in angiosperm cell walls), which also interacts with cellulose and lignin, is still poorly understood. Genes involved in the mannan biosynthetic pathway have been described in Arabidopsis, where cellulose synthase-like family A (CSLA) proteins synthesize the mannan backbone. The functional validation of orthologous genes responsible for the synthesis of this polysaccharide in woody plants and the effects of changing its content on secondary cell wall stability remain largely unstudied. In this study, I identify genes from woody plants that are responsible for mannan biosynthesis and evaluate the effect of modifying the expression of these genes on plant growth and cell wall structure. Using a combination of bioinformatic and phylogenetic tools, I identified putative genes from spruce (Picea engelmannii × glauca × sitchensis; PG29) and poplar (Populus tremula × Populus alba; 717) that encode CSLAs and GDP-mannose pyrophosphorylase (GMP) proteins. I functionally characterized these genes by evaluating if they were able to restore mannan content in the Arabidopsis csla 2,3,9 and vtc1-1 mutants, respectively. Then, I evaluated their function in wood by mutating the poplar CSLA and GMP candidate genes via CRISPR Cas9 or ectopically expressing the spruce gene candidates in poplar. In this work, I demonstrate that mannan content can be manipulated in tree stems either by altering the expression of CSLA or GMP encoding genes, without significantly affecting plant growth. This research provides new avenues to investigate the contribution of mannan alongside other common hemicelluloses in maintaining plant cell wall functionality.

Text

2024-05-09

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/88264

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/