The suberin transporter StABCG1 is required for barrier formation in potato leaves

Suberin is a hydrophobic biopolymer that acts as an internal and external diffusion and transpiration barrier in plants. It is involved in two phases of wound healing, i.e. initial closing layer formation and subsequent wound periderm development. Transcriptomic and metabolomic analyses of wounded potato leaf tissue revealed preferential induction of cell wall modifying processes during closing layer formation, accompanied by a highly active defense response. To address the importance of suberin in this process, we generated loss of function mutants by CRISPR-Cas9 editing the suberin transporter gene StABCG1. Both wound-induced StABCG1 transcript levels and suberin formation around wounded leaf tissue were reduced in CRISPR-lines. Moreover, wound-induced tissue damage was characterized by browning of wound-adjacent areas. Transcriptome analyses of these areas revealed up-regulation of genes encoding defense proteins and enzymes of the phenylpropanoid pathway. Levels of hydroxycinnamic acid amides, acting in defense and in cell wall reinforcement, were drastically enhanced in CRISPR compared to control plants. These results suggest that the reduction in suberin formation around wounded tissue leads to a loss of barrier function, resulting in tissue browning due to enhanced exposure to oxygen.