Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2008
Publication Date: 3/19/2008
Citation: Lulai, E.C., Suttle, J.C., Pederson, S.M. 2008. Regulatory involvement of abscisic acid in potato tuber wound-healing. Journal of Experimental Botany. 59(6):1175-1186. Interpretive Summary: Research was conducted to determine the regulatory involvement of the plant hormone abscisic acid (ABA) in potato wound-healing. Identification of the regulatory mechanisms controlling potato wound-healing is of great importance to growers, processors and consumers. Potato tubers that are cut for seed and tubers that are skinned, nicked and bruised during harvest and handling operations must rapidly wound-heal to avoid costly disease and blemish problems. The most important wound-healing processes are control of water loss and suberization of wound areas. Rapid reduction of water loss at wound sites is essential in preventing cell desiccation and death; live cells are required for all subsequent healing processes. Rapid wound-induced suberization of these cuts and damaged areas is essential in providing a protective barrier to block infection by various disease organisms. Despite the costly losses associated with slow or inadequate wound-healing, the plant hormones regulating these processes have not been determined. The plant hormone abscisic acid (ABA) is known to be associated with regulation of various biological processes including responses to various stresses. However, the involvement of ABA in wound-healing processes had not been determined until now. In this research fluridone, a directed inhibitor of ABA biosynthesis was used to produce ABA deficient tuber tissue. Tuber tissues were also treated with exogenous ABA and a combination of fluridone and ABA to determine if this plant hormone was involved in the wound-healing processes of suberization and control of cellular dehydration. Our results showed that tuber wounding resulted in a decrease followed by a large increase in ABA content during wound-healing. Fluridone treatments increased water loss during the wound-healing period and suppressed accumulation of both suberin biopolymers, suberin poly(phenolics) and suberin poly(aliphatics) which block bacterial and fungal infections. Combining ABA with the fluridone treatment restored these wound-healing processes. Treating tuber tissue with only ABA enhanced all of these wound-healing processes. These results are of great scientific importance in characterizing the physiology of wound-healing because they show that ABA is involved in regulating these processes and that wounding induces changes in tuber ABA content. The results are of practical importance because they advance information that may be used to elucidate the mechanisms regulating wound-healing for use in the development of future technologies to reduce infections and maintain quality for consumers.
Technical Abstract: Rapid wound-healing is crucial in protecting potato tubers from infection and dehydration. Wound-induced suberization and the accumulation of hydrophobic barriers to reduce water vapor conductance/loss are principle protective wound-healing processes. However, little is known about the biological factors that effect or regulate these processes. The objective of this research was to determine the involvement of abscisic acid (ABA) in the regulation of wound-induced suberization and tuber water vapor loss (dehydration). Analysis by liquid chromatography-mass spectrometry showed that ABA concentrations varied little throughout the tuber, but were slightly higher near the periderm and lowest in the pith. ABA concentrations increased then decrease during tuber storage. Tuber wounding induced changes in ABA content. ABA content in wound-healing tuber disks decreased after wounding, reached a minimum by 24 h, and then increased from the third through the seventh day after wounding. Wound-induced ABA accumulations were reduced by fluridone (FLD); an inhibitor of de novo ABA biosynthesis. Wound-induced phenylalanine ammonia lyase (PAL) activity was slightly reduced and the accumulation of suberin poly(phenolics) and poly(aliphatics) noticeably reduced in FLD-treated tissues. Addition of ABA to the FLD treatment restored PAL activity and suberization, indicating that ABA is involved in the regulation of these wound-healing processes. Similar experiments showed that ABA is involved in the regulation of water vapor loss, a process linked to wax accumulation in wound-healing tubers. Rapid reduction of water vapor loss across the wound surface is essential in preventing desiccation and death of cells at the wound site; live cells are required for suberization. These results unequivocally show that ABA is involved in the regulation of wound-induced suberization and the processes that protect surface cells from water vapor loss and death by dehydration.