Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2005
Publication Date: July 1, 2005
Citation: Suttle, J.C., Destefano Beltran, L.J., Knauber, D.C., Huckle, L.L. 2005. Changes in aba content, metabolism and expression of genes involved in aba biosynthesis and degradation in potato (solanum tuberosum l.) tuber meristems during chemically forced dormancy termination. 16th Triennial Confeence of the European Association for Potato Research. Poster 148. p.994-996. Technical Abstract: At harvest and for an indeterminate period thereafter, potato tubers will not sprout and are physiologically dormant. Potato tuber dormancy is thought to begin at the time of tuber initiation and is affected by both genotype and pre- and postharvest environmental factors (Burton, 1989). The onset of sprout growth following the termination of dormancy is accompanied by numerous physiological and biochemical changes; many of which are detrimental to the nutritional and processing qualities of potatoes. A greater understanding of the physiological bases of tuber dormancy control is required to identify and develop improved methods of sprout control. Although the molecular mechanisms regulating tuber dormancy are largely unknown, it is clear that endogenous plant hormones are intimately involved in potato tuber dormancy control (Suttle, 2004). In particular abscisic acid (ABA) plays a critical role in tuber dormancy control (Suttle and Hultstrand, 1994). ABA content is highest immediately after harvest and declines thereafter. Application of the phytoene desaturase inhibitor fluridone during microtuber development results in a drastic reduction of endogenous ABA content and premature sprouting. Exogenous ABA restores ABA levels and prevents precocious sprouting. Application of fluridone to fully developed dormant microtubers also results in precocious sprouting; indicating a role for sustained ABA biosynthesis in tuber dormancy maintenance. Despite its well characterized role in dormancy control, the cognate mechanisms controlling ABA biosynthesis and metabolism in tubers are unknown. ABA is synthesized from a carotenoid precursor according to the scheme illustrated in Figure 1 (Seo and Koshiba, 2002). Once formed, ABA is catabolized via a P450-mediated oxidative pathway to phaseic acid (PA) which is then reduced to dihydro-PA. Genes coding for the enzymes catalyzing these metabolic steps have been characterized from a number of plant tissues but have not been described in detail from potato tuber tissues. Using published sequence information and PCR techniques, genes coding for all post-zeaxanthin steps of ABA biosynthesis and PA formation (see figure) have been cloned and characterized from potato tuber tissues. Treatment of Russet Burbank tubers with bromoethane (BE) induces rapid and reproducible sprouting (Coleman, 1983). The mode of action of BE is unknown. In this presentation, we report on the effects of BE treatment on the endogenous contents of ABA, the rate of ABA metabolism and expression of genes involved in ABA homeostasis in meristems (eyes) isolated from potato (Solanum tuberosum L. cv. Russet Burbank) tubers.