Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2012
Publication Date: 3/15/2013
Citation: Suttle, J.C., Lulai, E.C., Huckle, L.L., Neubauer, J. 2013. Wounding of potato tubers induces increases in ABA biosynthesis and catabolism and alters expression of ABA metabolic genes. Journal of Plant Physiology. 170:560-566.
Interpretive Summary: The induction and regulation of wound-healing (WH) processes in potato tubers and other vegetables are of great nutritional and economic importance. The rapid accumulation of waxes to restrict water vapor loss and formation of protective suberin barriers to block opportunistic infection are crucial components of WH. Previous research from this project demonstrated that the plant hormone abscisic acid (ABA) is synthesized in response to physical damage and plays a critical role in the regulation of tuber WH. In this paper, the molecular mechanisms regulating wound-induced ABA synthesis and metabolism were determined in Russet Burbank tubers. An increase in ABA content was found after 48 hours and remained elevated 96 hours after wounding. Significant changes in the expression of genes encoding both ABA biosynthetic and metabolic enzymes was observed 3 hours after wounding and continued through 96 hours after wounding. Gene expression profiles suggested that the increase in ABA content after wounding is a result of increased activity of at least two biosynthetic enzymes. The effects of two other wound-induced hormones (jasmonic acid, ethylene) on ABA accumulation were also determined. An increase in jasmonic acid content was not required for wound-induced ABA accumulation. Treatment of wounded tubers with ethylene completely inhibited wound-induced ABA accumulation and alteration of ABA-related gene expression. These results are significant because ethylene is being evaluated as a sprout-control agent in stored potatoes in commercial storages where successful completion of tuber WH is critical.
Technical Abstract: The effects of physical wounding on ABA biosynthesis and catabolism and expression of genes encoding key ABA metabolic enzymes were determined in potato (Solanum tuberosum L.) tubers. An increase in ABA and ABA metabolite content was observed 48 h after wounding and remained elevated through 96 h. Wounding induced dramatic increases in the expression of the ABA metabolic genes encoding zeaxanthin epoxidase, 9-cis-epoxycarotenoid dioxygenase (NCED), and ABA-8'-hydroxylase. Although the patterns of wound-induced expression of individual genes varied, increased gene expression was observed within 3 h of wounding and remained elevated through 96 h. An apparent correlation between expression of the gene encoding zeaxanthin epoxidase and the increase in ABA content suggested that the wound-induced increase in ABA biosynthesis was regulated by both substrate availability and increased NCED activity. Inhibition of wound-induced jasmonic acid accumulation did not inhibit the subsequent increase in ABA content. Exogenous ethylene completely suppressed the wound-induced increase in ABA content and dramatically reduced wound-induced up-regulation of ABA metabolic genes. This study is the first to identify the molecular bases for increased ABA accumulation following physical trauma and highlight the complex physiological interactions between various wound-induced hormones.