The Architecture of Adaptive Lignin Biosynthesis Navigating Environmental Stresses in Plants

ABSTRACT In natural ecosystems, plants are under continuous environmental stresses, compromising plants' survival and propagation. Being sessile in nature, plants evolved various signalling pathways to cope with adverse changing environments, and to optimise their adaptation to terrestrial conditions. The plant cell wall, rich in polymers, is actively engaged in the signalling process. In this context, the phenylpropanoid pathway, producing protective secondary metabolites like flavonoids and lignin, played a crucial role in the early plants' colonisation on land. In this review, we highlighted the current knowledge and the impending gaps of lignin biosynthesis in plants, and the hydrophobic and impervious properties of lignin facilitating effective transportation of solutes and water within vascular system along with its significance to protect plants from environmental stressors either abiotic like temperature, drought, salinity and heavy metals or biotic such as herbivorous insects, root‐knot nematodes and phytopathogens. Additionally, the identification of essential biosynthetic genes that play a role in regulating lignin biosynthesis, as well as their contribution to improving stress tolerance through modifications in lignification of cell wall and biochemical mechanisms of lignin in the evolution of land plants are discussed, including the synergistic action of dirigent proteins and laccase in producing monolignol radicals. This discussion provided future research direction to develop genetic engineering approaches to improve lignin in terrestrial plants and develop stress‐tolerant plants that will improve the resilience and survival of plants under challenging environmental conditions.