S05 - Session O1 - Keynote: Rose vase life and how the physiological and genetic approaches on vase life can help breeders and producers

Authors: Yunhe Jiang, Xiaoming Sun, Xiaofeng Zhou, Yanjie Xu, Chao Ma, Nan Ma, Bo Hong, Junping Gao *

Flowers are unique and highly evolved organs that help maximize the reproductive success of flowering plants. For floral industry, on the other hand, flowers are the most important economical organs for floral crops. The process of flower senescence largely determines the ornamental and economic value of a flower. Flower senescence is a highly programmed event, representing the final stage of petal development, and culminates in the death of the petal. Typical signs of flower senescence include petal color change, rolling, wilting, and abscission. Given petals are evolutionarily derived from leaves, and so, not surprisingly, petal senescence shares common physiological and biochemical processes with leaf senescence. However, petal and leaf senescence are also distinct from each other in a number of ways. Recently, we uncovered the underlying mechanisms of both abscission and wilting in roses. We found that auxin could delay petal abscission via activating an auxin responsive transcription factor ARF7, which enhancing expression of a sucrose transportor gene, SUC2, in abscission zone. Increased level of SUC2 led to sucrose uptake in petals and sequentially postponed petals shedding. Meanwhile, we found that petal wilting was regulated by the circadian-dependent mitochondrial ROS (mtROS) homeostasis. In rose petals, the H2O2 level exhibits a typical circadian rhythmicity, which is opposite that observed in leaves but is consistent with the respiratory rate of petals. A PIF8-BBX28 transcription cascade is activated in a circadian-dependent manner and controlled expression of a succina dehydrogenase gene (SDH1). SDH1 is a highly conserved subunit of Mitochondrial Complex II and the electron transport chain, and thus has a central role in mtROS homeostasis. We considered that PIF8-BBX28 represents a surveillance component to constrain activity of Mitochondrial Complex II to avoid excessive mtROS production in petals. These findings provide new insights in flower senescence and could be beneficial for industry of rose flowers in the future.