Inhibitors of tri- and tetra- polyamine oxidation, but not oxidation, impair the initial stages of wound-induced suberization

Authors: Lulai, Edward; Young, Linda; Fugate, Karen; Neubauer, Jonathan; Campbell, Larry

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2019
Publication Date: 12/17/2019
Citation: Lulai, E.C., Young, L.L., Fugate, K.K., Neubauer, J., Campbell, L.G. 2019. Inhibitors of tri- and tetra- polyamine oxidation, but not oxidation, impair the initial stages of wound-induced suberization. Journal of Plant Physiology. 246-247:153092. https://doi.org/10.1016/j.jplph.2019.153092.
DOI: https://doi.org/10.1016/j.jplph.2019.153092

Interpretive Summary: Tuber wound healing is critical in protecting freshly harvested potatoes and cut seed from infection, desiccation, defect development and variety of other market quality problems causing well over $330 million per year. We used a variety of chemicals that block/inhibit specific steps within a biological system that degrades certain amino acids after potato tuber wounding. We determined that changes in overall content of the degradation products did not affect potato tuber wound healing. However, we found that inhibition of the oxidation of these degradation products significantly reduced the wound-induced formation of barriers to bacterial infection at the wound site. These results suggest that the enhancement of this process may serve as a modulating point to improve wound healing, reduce losses and improve quality for the consumer.

Technical Abstract: The mechanisms regulating and modulating potato wound-healing processes are of great importance in reducing tuber infections, reducing shrinkage and maintaining quality and nutritional value for growers and consumers. Wound-induced changes in tuber polyamine metabolism have been linked to the modulation of wound healing (WH) and in possibly providing the crucial amount of H2O2 required for suberization processes. In this investigation we determined the effect of inhibition of specific steps within the pathway of polyamine metabolism on polyamine content and the initial accumulation of suberin polyphenolics (SPP) during WH. The accumulation of SPP represents a critical part of the beginning or inchoate phase of tuber WH during closing-layer formation because it serves as a barrier to bacterial infection and is a requisite for the accumulation of suberin polyaliphatics which provde the barrier to fungal infection. Results showed that inhibitor treatments causing changes in polyamine content did not influence wound-induced accumulation of SPP. Treatment with inhibitors of arginine and ornithine decarboxylase, and diamine oxidase had no effect on SPP accumulation. However, treatment with guazatine, a potent inhibitor of polyamine oxidase (PAO), and methylglyoxal-bis(guanylhydrazone, a putative inhibitor of S-adenosylmethione decarboxylase which may also cross react to inhibit PAO, dramatically reduced SPP accumulation presumably by blockage of essential H2O2 production within the WH cell wall. These results are of great importance in understanding the mechanisms modulating WH and ultimately controlling related infections and associated postharvest losses.