ATP-binding cassette-like transporters are involved in the transport of lignin precursors across plasma and vacuolar membranes

Biology Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 12/2010; 107(52):22728-33. DOI: 10.1073/pnas.1007747108
Source: PubMed


Lignin is a complex biopolymer derived primarily from the condensation of three monomeric precursors, the monolignols. The synthesis of monolignols occurs in the cytoplasm. To reach the cell wall where they are oxidized and polymerized, they must be transported across the cell membrane. However, the molecular mechanisms underlying the transport process are unclear. There are conflicting views about whether the transport of these precursors occurs by passive diffusion or is an energized active process; further, we know little about what chemical forms are required. Using isolated plasma and vacuolar membrane vesicles prepared from Arabidopsis, together with applying different transporter inhibitors in the assays, we examined the uptake of monolignols and their derivatives by these native membrane vesicles. We demonstrate that the transport of lignin precursors across plasmalemma and their sequestration into vacuoles are ATP-dependent primary-transport processes, involving ATP-binding cassette-like transporters. Moreover, we show that both plasma and vacuolar membrane vesicles selectively transport different forms of lignin precursors. In the presence of ATP, the inverted plasma membrane vesicles preferentially take up monolignol aglycones, whereas the vacuolar vesicles are more specific for glucoconjugates, suggesting that the different ATP-binding cassette-like transporters recognize different chemical forms in conveying them to distinct sites, and that glucosylation of monolignols is necessary for their vacuolar storage but not required for direct transport into the cell wall in Arabidopsis.

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Available from: Chang-Jun Liu, Jan 08, 2016
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    • "However, the inhibition of ABC transporters in different xylem tissues (poplar, hybrid poplar, Japanese cypress and pine) using vanadate did not affect the transport of coniferin, whereas proton gradient erasers markedly reduced the transport, suggesting an export via proton-coupled antiporters (Tsuyama et al., 2013). The passive diffusion is supported by in vitro observations of the partitioning of lignin monomers by immobilized liposomes and lipid bilayer discs (Boija and Johansson, 2006; Boija et al., 2007); however, this mechanism is considered unlikely to play a major role in the mobilization of monolignols (Miao and Liu, 2010). Vesicle-associated secretion of lignin monomers was initially supported by the labelling of ER-and Golgi-derived vesicles in xylem TEs when feeding with tritium-labelled phenylalanine and subsequent autoradiographical imaging using electron microscopy (Pickett-Heaps, 1968; Fujita and Harada, 1979; Takabe et al., 1985). "
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