Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2003
Publication Date: 3/8/2004
Citation: LAW, R.D., SUTTLE, J.C. CHANGES IN HISTONE H3 AND H4 MULTI-ACETYLATION DURING NATURAL AND FORCED DORMANCY BREAK IN POTATO TUBERS. PHYSIOLOGIA PLANTARUM. 2004. V. 120. P. 642-649. Interpretive Summary: For an indeterminate period of time following harvest, potatoes will not sprout and are physiologically dormant. Dormancy is gradually lost during postharvest storage and the resultant sprouting is detrimental to the nutritional and processing qualities of potatoes. Because of this, sprouting results in severe financial loss to producers. Currently sprouting is controlled through the use of synthetic sprout inhibitors. The research being conducted in this lab is directed towards 1.) identifying key physiological processes that naturally regulate tuber dormancy and, ultimately, 2.) modifying these processes genetically thereby eliminating the need for artificial sprout suppression. At the cellular level, our research is directed toward identifying the molecular bases for low rates of RNA synthesis that accompany and possible regulate tuber dormancy. In this paper, the effects of tuber dormancy on histone acetylation have been determined during natural and chemically forced dormancy termination. Histone acetylation is a reversible process that has been linked to regulation of RNA synthesis in other organisms. Our research is the first to demonstrate that significant changes in histone acetylation occur as tuber dormancy ends and RNA synthesis increases during prolonged (ca. 6 months) cold storage. Similar changes in histone acetylation were found to accompany rapid (ca. 9 day), chemically induced dormancy termination. Together with earlier published studies from this laboratory, these studies are beginning to define the cellular bases for dormancy-imposed growth arrest and may provide insight into new mechanisms to regulate this economically important process in potatoes.
Technical Abstract: The effects of postharvest storage and dormancy progression on histone acetylation patterns were examined in potato (Solanum tuberosum L. cv. Russet Burbank) tubers. Storage of field-grown tubers at 3°C in the dark resulted in the progressive loss of tuber meristem dormancy, defined as measurable growth after transfer to 20°C for 7 days. Dormancy emergence was concomitant with steady and gradual increases in histone H3.1 and H3.2 multi-acetylation, and transient increases in H4 multi-acetylation, peaking 4 to 5 months postharvest. Treatment of dormant tubers with bromoethane (BE) resulted in rapid loss of dormancy over 9 days. Similar to cold-stored field-grown tubers, dormancy break in BE-treated tubers occurred at the same time as transient rises in H3.1/H4 and H3.2 multi-acetylation, peaking at days 3 to 4 and 4 to 5, respectively. BE treatment also resulted in small increases in RNA synthesis at day 6, and a 3-fold, sustained activation of DNA synthesis thereafter. A defined sequence of epigenetic events, beginning with previously-characterized transient cytosine demethylation, followed by increased H3 and H4 histone acetylation and ultimately, tuber meristem reactivation, may thus exist in potatoes during dormancy exit and resumption of rapid growth.