Auxin as an architect of the pectin matrix.

Auxin is a versatile plant growth regulator that triggers multiple signalling pathways at different spatial and temporal resolutions. A plant cell is surrounded by the cell wall, a complex and dynamic network of polysaccharides. The cell wall needs to be rigid to provide mechanical support and protection and highly flexible to allow cell growth and shape acquisition. The modification of the pectin components, among other processes, is a mechanism by which auxin activity alters the mechanical properties of the cell wall. Auxin signalling precisely controls the transcriptional output of several pectin remodelling enzyme-encoded genes, their local activity and pectin deposition and modulation in different developmental contexts. This review examines the mechanism of auxin activity in regulating pectin chemistry at organ, cellular and subcellular levels across diverse plant species and asks questions that remain to be addressed to fully understand the interplay between auxin and pectin in plant growth and development.