Hunting monolignol transporters: membrane proteomics and biochemical transport assays with membrane vesicles of Norway spruce

• Published in: Journal of experimental botany 2020-10, Vol.71 (20), p.6379-6395
• Main Authors: Väisänen, Enni, Takahashi, Junko, Obudulu, Ogonna, Bygdell, Joakim, Karhunen, Pirkko, Blokhina, Olga, Laitinen, Teresa, Teeri, Teemu H, Wingsle, Gunnar, Fagerstedt, Kurt V, Kärkönen, Anna
• Format: Article
• Language: English
• Subjects: abc transporters; Biochemistry and Molecular Biology; Biokemi och molekylärbiologi; cambial sap; coniferyl-alcohol; differentiating xylem; expression analysis; lignification; Lignin; Lignin biosynthesis; lignin precursors; monolignol transport; Norway; p-coumaroyl transferase; Picea; Plant Sciences; plasma membrane; plasma-membranes; protein; Proteomics; Research Papers; transporter proteins; Trävetenskap; Wood Science; Xylem
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/eraa368

Both the mechanisms of monolignol transport and the transported form of monolignols in developing xylem of trees are unknown. We tested the hypothesis of an active, plasma membrane-localized transport of monolignol monomers, dimers, and/or glucosidic forms with membrane vesicles prepared from developing xylem and lignin-forming tissue-cultured cells of Norway spruce (Picea abies L. Karst.), as well as from control materials, comprising non-lignifying Norway spruce phloem and tobacco (Nicotiana tabacum L.) BY-2 cells. Xylem and BY-2 vesicles transported both coniferin and p-coumaryl alcohol glucoside, but inhibitor assays suggested that this transport was through the tonoplast. Membrane vesicles prepared from lignin-forming spruce cells showed coniferin transport, but the Km value for coniferin was much higher than those of xylem and BY-2 cells. Liquid chromatography-mass spectrometry analysis of membrane proteins isolated from spruce developing xylem, phloem, and lignin-forming cultured cells revealed multiple transporters. These were compared with a transporter gene set obtained by a correlation analysis with a selected set of spruce monolignol biosynthesis genes. Biochemical membrane vesicle assays showed no support for ABC-transporter-mediated monolignol transport but point to a role for secondary active transporters (such as MFS or MATE transporters). In contrast, proteomic and co-expression analyses suggested a role for ABC transporters and MFS transporters.