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United States Department of Agriculture

Agricultural Research Service

Research Project: IDENTIFICATION AND MANIPULATION OF POSTHARVEST PHYSIOLOGICAL AND MOLECULAR PROCESSES CONTROLLING POTATO NUTRITIONAL AND MARKET QUALITY

Location: Sugarbeet and Potato Research

Title: Coordinate expression of AOS genes and JA accumulation: JA is not required for initiation of closing layer in wound healing tubers

Authors
item Lulai, Edward
item Huckle, Linda
item Neubauer, Jonathan
item Suttle, Jeffrey

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 3, 2010
Publication Date: June 6, 2011
Citation: Lulai, E.C., Huckle, L.L., Neubauer, J., Suttle, J.C. 2011. Coordinate expression of AOS genes and JA accumulation: JA is not required for initiation of closing layer in wound healing tubers. Journal of Plant Physiology. 168:976-982.

Interpretive Summary: Potato tubers are wounded upon harvest, handling and seed cutting. These wounds must heal quickly to avoid costly infection and deterioration of food quality. Mechanisms that may hasten/regulate these healing processes are of great importance. Jasmonic acid (JA) is a potent wound-induced regulator of various responses in leaf tissue. However, little is known about the role of JA in potato tuber wound healing, including the increased expression/up-regulation of genes involved JA biosynthesis, the coordinate accumulation of JA and its possible involvement in regulating formation of a protective barrier to disease called the closing layer. In this study, the effects of wounding on JA content, expression of JA biosynthetic genes, and the involvement of JA in the initiation of closing layer formation in potato (Solanum tuberosum L. cv. Russet Burbank) tubers were determined. Also, the role of ABA (a hormone known to regulate a range wound-healing processes) in wound-induced JA accumulation was examined. The JA content found in resting/non-wounded tuber tissues was low [<3 ng (g F.W.)-1]. Importantly, only two hours after wounding, the JA content was found to rapidly increase by > 5-fold, reached a maximum between 4-6 hours after wounding, and then declined to near that found in resting non-wounded tubers. Tuber age (storage duration) had little effect on the pattern of JA accumulation. These results indicate that the capability to form JA is preserved during typical tuber storage and its rapid formation suggests involvement in regulation of processes occurring in the early stages of tuber wound response. The expression of genes specifically involved in JA biosynthesis were found to dramatically increase upon wounding and reached a maximum 2-4 hours after wounding and declining thereafter. These results imply a need for direct and rapid coordination of gene expression and JA formation in wound responding tissues. A one-hour water wash of tuber tissues immediately after wounding resulted in a 94 % inhibition of wound-induced JA accumulation. Neither JA treatment nor inhibition of JA accumulation in tuber tissues affected closing layer development; this indicated that JA was not essential for the initiation of this primary barrier to infection. ABA treatment did not restore JA accumulation in washed tuber tissues suggesting that leaching of endogenous ABA was either not involved or not solely involved in this loss of JA accumulation. Collectively, these results suggest that JA is not required for the induction of rapid wound responses related to the initiation of closing layer development in wound-healing tuber tissue. However, these results do not exclude the possibility, and may be interpreted to suggest, that JA is involved in regulating important protective wound responses induced to occur before initiation of development of the closing layer barrier to infection.

Technical Abstract: Wounding induces a series of coordinated physiological responses essential for protection and healing of the damaged tissue. Wound-induced formation of jasmonic acid (JA) is important in defense responses in leaves, but comparatively little is known about the induction of JA biosynthesis and its role(s) in tuber wound-healing. In this study, the effects of wounding on JA content, expression of JA biosynthetic genes, and the involvement of JA in the initiation of closing layer formation in potato (Solanum tuberosum L. cv. Russet Burbank) tubers were determined. In addition, the role of ABA in wound-induced JA accumulation was examined. The basal JA content in non-wounded tuber tissues was low [<3 ng (g F.W.)-1]. Two hours after wounding, the JA content increased by > 5-fold, reached a maximum between 4-6 hours after wounding, and declined to near-basal levels thereafter. Tuber age (storage duration) had little effect on the pattern of JA accumulation. The expression of the JA biosynthetic genes (StAOS2, StAOC, and StOPR3) was dramatically increased by wounding reaching a maximum 2-4 hours after wounding and declining thereafter. A one-hour aqueous wash of tuber discs immediately after wounding resulted in a 94 % inhibition of wound-induced JA accumulation. Neither JA treatment nor inhibition of JA accumulation affected suberin poly(phenolic) accumulation during closing layer development indicating that JA was not essential for the initiation of primary suberization. ABA treatment did not restore JA accumulation in washed tuber tissues suggesting that leaching of endogenous ABA was either not involved or not solely involved in this loss of JA accumulation. Collectively, these results suggest that JA is not required for the induction of rapid wound responses related to the initiation of suberization during closing layer development in wound-healing tuber tissue but does not exclude the possibility that JA may be involved in subsequent down-stream wound-related processes.

Last Modified: 4/16/2014
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