Hormonal crosstalk in the regulation of lignification: where do we stand?

Lignification is a central process affecting plant growth, development, and stress responses. An intricate network of hormonal signals tightly regulates these processes. Several phytohormones have been demonstrated to function as important modulators of the lignin biosynthesis pathway, but their crosstalk is largely elusive. Increasing evidence of hierarchical transcriptional networks in lignification and the interaction of transcriptional regulation with different phytohormones highlights the need to emphasize this critical regulatory aspect of lignification. The hormones adjust lignification by modifying gene expression, enzyme activity, and the interaction between different metabolic pathways. This review summarizes the status of the principal hormonal control of lignification at the individual level, and also accentuates their crosstalk and the transcriptional control. Additionally, the role of reactive oxygen species (ROS) in connecting lignification with hormonal regulation is discussed. This review not only contributes to basic plant biology but also paves the way for the development of crops with improved stress tolerance and specialized lignin qualities for industrial applications.