The effects of copper deficiency on lignification, xylem vessel structure, and hydraulic traits in hybrid Poplar

Authors: Hunter, Cameron; SUN, ZIMOU - University Of British Columbia; MANSFIELD, SHAWN - University Of British Columbia; SHAHBAZ, MUHAMMAD - Colorado State University; PILON, MARINUS - Colorad0 State University; Gleason, Sean

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2023
Publication Date: 9/14/2023
Citation: Hunter, C., Sun, Z., Mansfield, S., Shahbaz, M., Pilon, M., Gleason, S.M. 2023. The effects of copper deficiency on lignification, xylem vessel structure, and hydraulic traits in hybrid Poplar. Plant Physiology. 175(5). Article e14006. https://doi.org/10.1111/ppl.14006.
DOI: https://doi.org/10.1111/ppl.14006

Interpretive Summary: Copper is required for many plant physiological processes. Here we address the role of copper in lignin synthesis, which is a "structural" carbohydrate needed to maintain the elasticity and strength of plant leaves, stems, and roots. We found that withholding copper from poplar plants resulted in a shift in the type of lignin synthesized by the plant, such that the lignin produced was more elastic (less stiff). However, the leaf cell walls and whole-stem tissues of copper deficient plants were stiffer than the leaves and stems of plants that had received sufficient copper. This is the opposite result of what would be expected given the shift in lignin synthesis that was observed. We speculate that Cu deficient plants compensated for more elastic lignin by upregulating other structural carbohydrates, such as cellulose and hemicellulos.

Technical Abstract: Copper homeostasis is integral to many plant physiological processes, including lignification of plant cell walls. This link occurs through copper’s role as a cofactor in the apoplastic laccase enzymes that oxidize monolignols that then polymerize to form the hydrophobic lignin polymer, which provides rigidity and strength to the water transport system. In this study, we investigated the effect of copper deficiency on lignin content and chemistry in poplar stems. We also examined the effect of copper deficiency on the stiffness of stem wood and leaf cell walls. Copper deficiency resulted in significant shift in the syringyl to guaiacyl monomer ratio of stem xylem, but stem modulus of elasticity was not affected. Accompanying these stem traits, copper deficient leaves had markedly stiffer mesophyll cell walls. Our results may reflect a novel response response in poplar whereby structural stiffness and mechanical stability is maintained in the face of Cu deficiency and reduction syringly monomer synthesis.