Page Banner

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: Kinetics and localization of wound-induced DNA biosynthesis in potato tuber

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

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 23, 2014
Publication Date: November 1, 2014
Citation: Lulai, E.C., Neubauer, J., Suttle, J.C. 2014. Kinetics and localization of wound-induced DNA biosynthesis in potato tuber. Journal of Plant Physiology. 171:1571-1575.

Interpretive Summary: Potato tubers (Solanum tuberosum L.) are wounded upon harvest, handling and seed cutting. These wounds result in well over $300 million per year in losses due to damage related defects and associated deterioration. Large additional losses are also incurred because of incalculable wound-related disease defects that are not included in this calculated loss. Tuber wounding induces a cascade of important biological responses that are involved in processes required to heal and protect surviving plant tissues. However, little is known about the coordinate induction of these processes, including essential wound-induced DNA synthesis, yet they play critical roles in maintaining marketability of the harvested crop and tubers cut for seed. A sensitive “Click-iT EdU Assay” employing incorporation of the thymidine ( a DNA component) analog, 5-ethynyl-2’-deoxyuridine (EdU), in conjunction with 4’,6-diamindino-2-phenylindole (DAPI) counter labeling, was employed to objectively identify and determine the time course and spatial distribution of tuber nuclei that were wound induced to synthesize DNA as part of the healing process. Nuclei are the cellular components that house hereditary DNA material and serve as the administrative center of the cell and are responsible for cellular activities including wound healing. Cells whose nucleus have been signaled to synthesize DNA to support production of new cells through obligate cell division processes, such as that required for wound healing, are said to be in the “S-phase” or synthesis phase of the cell cycle. Both procedures for localizing and identifying nuclei, i.e. all nuclei and those induced to synthesize DNA, are rapid and sensitive. Following wounding, EdU incorporation (indicating DNA synthesis) was not detectable until after 12 h, rapidly reached a maximum at about 18 h and then declined to near zero at 48 h. About 28 % of the nuclei were EdU labeled at 18 h reflecting the proportion of cells in S-phase of the cell cycle at that time point. During the ~ 30 h in which induced cells were progressing through S-phase, DNA synthesis extended 7 to 8 cell layers below the wound surface. Cessation of nuclear DNA synthesis occurred about 4 d prior to completion of wound closing layer formation; a process where existing cells are rapidly laminated with a protective suberin coating. Initiation of formation of new cells laminated with a protective suberin coating (i.e. wound periderm development) followed at 7 d, i.e. about 5 d after cessation of nuclear DNA biosynthesis; at this time a layer of mother cells (i.e. phellogen) developed and cell division (meristematic activity) was detected via the production of new protective cells (phellem cells). Seven to eight layers of these newly formed protective phellem cells were generated, matching the depth of wound-induced DNA synthesis which ended a full 5 d prior to this. Collectively, these results provide new insight into the coordination of cellular processes involved in tuber wound-healing. These results clearly illustrate where DNA synthesis for future cell division fits into the time course for wound-healing process and how it relates to the depth of the wound-healing response relative to the wound surface. These biological relationships may be exploited in the development of future technologies that are needed to regulate/hasten and enhance the efficacy of wound healing to reduce infection and deterioration of tuber quality.

Technical Abstract: Tuber wounding induces a cascade of biological responses that are involved in processes required to heal and protect surviving plant tissues. Little is known about the coordination of these processes, including essential wound-induced DNA synthesis, yet they play critical roles in maintaining marketability of the harvested crop and tubers cut for seed. A sensitive “Click-iT EdU Assay” employing incorporation of the thymidine analog, 5-ethynyl-2’-deoxyuridine (EdU), in conjunction with 4’,6-diamindino-2-phenylindole (DAPI) counter labeling, was employed to objectively identify and determine the time course and spatial distribution of tuber nuclei that were wound-induced to enter S-phase of the cell cycle. Both labeling procedures are rapid and sensitive in situ. Following wounding, EdU incorporation (indicating DNA synthesis) was not detectable until after 12 h, rapidly reached a maximum at about 18 h and then declined to near zero at 48 h. About 28 % of the nuclei were EdU labeled at 18 h reflecting the proportion of cells in S-phase of the cell cycle. During the ~ 30 h in which induced cells were progressing through S-phase, de novo DNA synthesis extended 7 to 8 cell layers below the wound surface. Cessation of nuclear DNA synthesis occurred about 4 d prior to completion of wound closing layer formation. Initiation of wound periderm development followed at 7 d, i.e. about 5 d after cessation of nuclear DNA biosynthesis; at this time the phellogen developed and meristematic activity was detected via the production of new phellem cells. Collectively, these results provide new insight into the coordination of cellular processes involved in tuber wound-healing.

Last Modified: 9/22/2014
Footer Content Back to Top of Page