Active Transport of Lignin Precursors into Membrane Vesicles from Lignifying Tissues of Bamboo

Abstract

: Lignin is the second most abundant natural polymer on Earth and is a major cell wall component in vascular plants. Lignin biosynthesis has three stages: biosynthesis, transport, and polymerization of its precursors. However, there is limited knowledge on lignin precursor transport, especially in monocots. In the present study, we aimed to elucidate the transport mode of lignin monomers in the lignifying tissues of bamboo (Phyllostachys pubescens). The growth manners and lignification processes of bamboo shoots were elucidated, which enabled us to obtain the lignifying tissues reproducibly. Microsomal membrane fractions were prepared from tissues undergoing vigorous lignification to analyze the transport activities of lignin precursors in order to show the ATP-dependent transport of coniferin and p-glucocoumaryl alcohol. The transport activities for both precursors depend on vacuolar type H+-ATPase and a H+ gradient across the membrane, suggesting that the electrochemical potential is the driving force of the transport of both substrates. These findings are similar to the transport properties of these lignin precursors in the differentiating xylem of poplar and Japanese cypress. Our findings suggest that transport of coniferin and p-glucocoumaryl alcohol is mediated by secondary active transporters energized partly by the vacuolar type H+-ATPase, which is common in lignifying tissues. The loading of these lignin precursors into endomembrane compartments may contribute to lignification in vascular plants.

Hrip1 mediates rice cell wall fortification and phytoalexins elicitation to confer immunity against Magnaporthe oryzae

“…Some schools of thought suggest active transport mechanisms are involved in moving glycosylated lignin monomers mediated by ABC transporters. Other studies have linked monomeric transport via passive diffusion (Miao and Liu, 2010;Tsuyama et al, 2013;Shimada et al, 2021). Notwithstanding these contrasting views, monolignol transport is crucial for lignification.…”

Grass lignin: biosynthesis, biological roles, and industrial applications

“…Monolignol glucosides are synthesized by UDP-glycosyltransferases, and are a putative storage configuration of monolignols (Dima et al, 2015). Glycosylated monolignols are found in vacuoles of A. thaliana leaf cells (Dima et al, 2015), and are transported into the apoplast during cell lignification in a gymnosperm (Vaisanen et al, 2020), dicots (Morikawa et al, 2010;Tsuyama et al, 2013Tsuyama et al, , 2019, and recently in the monocot Phyllostachys pubescens (Shimada et al, 2021). More research is needed to determine if cereals deploy sequestered monolignol glucosides after injury or pathogen detection; a mechanism not yet supported by genetic evidence (Jeon et al, 2022).…”

Production and Application of Cellulose, Dietary Fiber, and Nanocellulose from Bamboo Shoot

“…Wherein, the transport activities for coniferin and β-glucocoumaryl alcohol depend on vacuolar type H + -ATPase and a H + gradient across the membrane. Thus, the transportation is mediated by secondary active transporters energized partly by the vacuolar-type H + -ATPase [24].…”