Changes in well-defined phases of bud dormancy may involve shifts in carbohydrate metabolism

Authors: Chao, Wun; Anderson, James; Horvath, David

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2007
Publication Date: 7/1/2007
Citation: Chao, W.S., Anderson, J.V., Horvath, D.P. 2007. Changes in well-defined phases of bud dormancy may involve shifts in carbohydrate metabolism. [Abstract]. Plant Biology & Botany 2007 Program & Abstract Book. P26013. p.150.

Interpretive Summary: Underground adventitious buds (located on the crown and roots) of leafy spurge are 1) maintained in a quiescent state through correlative inhibition (paradormancy) during the normal growing season, 2) inhibited from initiating post-senescence shoot growth in the fall by innate dormancy (endodormancy), and 3) maintained in a state of ecodormancy during overwintering. Carbohydrates appear to be involved in the development and release of bud dormancy during these seasonal cycles. In this study, relationships between carbohydrate metabolism and dormancy were examined in underground adventitious buds of leafy spurge in response to both seasonal signals and growth induction by decapitation. Seasonal signals caused sucrose levels to increase in Nov and Dec, whereas starch levels decreased progressively from Aug to Dec. In contrast, after paradormancy release, sucrose levels decreased significantly one day after decapitation and stayed at similar levels until day 5. Starch levels also decreased quickly and continuously from day 1 to day 5 after decapitation. Real-time PCR was used to determine if shifts in carbohydrate contents correlate with the expression levels of carbohydrate metabolism genes. Our results indicated that many of these genes were differentially-regulated. Among them, a specific beta-amylase gene increased 100-fold after growth induction by decapitation. During the seasonal cycle, the transcript increased 16,000-fold when comparing December to July samples. Combined, these results indicate that this beta-amylase gene may play an important role in starch degradation during paradormancy release and endodormancy development.

Technical Abstract: Underground adventitious buds (located on the crown and roots) of leafy spurge are 1) maintained in a quiescent state through correlative inhibition (paradormancy) during the normal growing season, 2) inhibited from initiating post-senescence shoot growth in the fall by innate dormancy (endodormancy), and 3) maintained in a state of ecodormancy during overwintering. Carbohydrates appear to be involved in the development and release of bud dormancy during these seasonal cycles. In this study, relationships between carbohydrate metabolism and dormancy were examined in underground adventitious buds of leafy spurge in response to both seasonal signals and growth induction by decapitation. Seasonal signals caused sucrose levels to increase in Nov and Dec, whereas starch levels decreased progressively from Aug to Dec. In contrast, after paradormancy release, sucrose levels decreased significantly one day after decapitation and stayed at similar levels until day 5. Starch levels also decreased quickly and continuously from day 1 to day 5 after decapitation. Real-time PCR was used to determine if shifts in carbohydrate contents correlate with the expression levels of carbohydrate metabolism genes. Our results indicated that many of these genes were differentially-regulated. Among them, a specific beta-amylase gene increased 100-fold after growth induction by decapitation. During the seasonal cycle, the transcript increased 16,000-fold when comparing December to July samples. Combined, these results indicate that this beta-amylase gene may play an important role in starch degradation during paradormancy release and endodormancy development.