Current Understanding of the Genetics and Molecular Mechanisms Regulating Wood Formation in Plants

Abstract

Unlike herbaceous plants, woody plants undergo volumetric growth (a.k.a. secondary growth) through wood formation, during which the secondary xylem (i.e., wood) differentiates from the vascular cambium. Wood is the most abundant biomass on Earth and, by absorbing atmospheric carbon dioxide, functions as one of the largest carbon sinks. As a sustainable and eco-friendly energy source, lignocellulosic biomass can help address environmental pollution and the global climate crisis. Studies of Arabidopsis and poplar as model plants using various emerging research tools show that the formation and proliferation of the vascular cambium and the differentiation of xylem cells require the modulation of multiple signals, including plant hormones, transcription factors, and signaling peptides. In this review, we summarize the latest knowledge on the molecular mechanism of wood formation, one of the most important biological processes on Earth.

Exploring the Seasonal Dynamics and Molecular Mechanism of Wood Formation in Gymnosperm Trees

“…Threshold temperature depends on the species and age [24,25]. Three to four weeks after cambium reactivation, cambium cells are actively dividing, and xylem differentiation occurs through cell expansion, SCW formation, and PCD [7,25]. Temperatures favorable for cambium activity are about 17 • C for Scots pine and about 25 • C for Chinese red pine [19,26].…”

“…Suppression of the abiotic stress response in early spring was hypothesized to trigger the active formation of wood through the inhibition of Leaf Curling Responsiveness (LCR) and MYB5, which are involved in salt stress and heat stress response, respectively [49,53,54]. Cell expansion is the first step of xylem cell differentiation [7]. In Norway spruce, cambium reactivation begins with the expression of alpha-Expansins (EXPAs), a marker of cell wall expansion [13,55].…”

“…SCW formation includes coordinated transcriptional regulation of genes involved in cellulose, hemicellulose, and lignin biosynthesis, which requires a multifaceted and multilayered transcriptional regulatory program that is active in the growing season [7,13,36,[56][57][58]. MYB26 regulates NST1 and NST2, which are responsible for SCW formation.…”

“…Wood (i.e., secondary xylem) is composed primarily of cellulose, xylan, and lignin. Wood formation begins with the cell division of the vascular cambium into secondary xylem inside and secondary phloem outside [7]. Next, xylem daughter cells expand to their final shape and size before secondary cell wall (SCW) deposition and programmed cell death (PCD) occur [7,8].…”

“…Wood formation begins with the cell division of the vascular cambium into secondary xylem inside and secondary phloem outside [7]. Next, xylem daughter cells expand to their final shape and size before secondary cell wall (SCW) deposition and programmed cell death (PCD) occur [7,8]. Wood formation in trees is a cyclical process that is strongly influenced by seasonal changes in environmental conditions, such as day length and temperature.…”