Suberization

Suberization is the process by which plant cells deposit suberin, a hydrophobic biopolymer, in their cell walls. This deposition occurs during normal development in the outer layers of the periderm, in the root endodermis, and in tissues formed in response to wounding or pathogen attack. In woody plants, the cork cambium (phellogen) produces phellem cells that become suberized; a suberin-rich cork layer forms the outer bark, reducing permeability and providing protection.

Suberin has two major structural domains: a polyaliphatic domain consisting of long-chain fatty acids, ω-hydroxy acids, and α,ω-dicarboxylic acids; and a polyphenolic domain rich in ferulates. The two domains assemble into a laminated, hydrophobic barrier within the cell wall. Monomers are synthesized in plastids and endoplasmic reticulum, transported to the wall by lipid transfer proteins and ABC transporters, and polymerized by oxidative enzymes such as peroxidases and laccases.

Suberization in roots contributes to the Casparian strip and endodermal barrier, limiting apoplastic flow and helping regulate mineral uptake. Developmentally, endodermal suberization proceeds with maturation; in response to wounding or drought, suberin deposition can be accelerated to seal damaged tissue and impede pathogen ingress.

Genetic control: Suberin biosynthesis and deposition are regulated by transcription factors from the MYB and SHINE families, and by transporters such as ABCG and enzymes like GPAT5 and CYP86A1. The process is of ecological and agricultural importance, affecting water relations, resistance to soil pathogens, and postharvest preservation.