Molecular Mechanisms of Petal Senescence in Ornamental Plants

Abstract

Flower longevity is one of the most important traits for ornamental plants. Ethylene plays a crucial role in petal senescence in many plant species. Genes involved in ethylene biosynthesis, ethylene perception, and its signal transduction have been identified in several ornamental plants. Genetic modification of ethylene signaling genes has successfully improved flower longevity in several plant species. In contrast, regulatory mechanisms of petal senescence in flowers that show ethylene-independent senescence remain largely unknown. Japanese morning glory (Ipomoea nil) is a proposed model plant for ethylene-independent petal senescence, and an important role of autophagy in petal senescence has been highlighted in this plant. This review focused on our recent findings on ethylene signaling and our attempts to identify factors regulating ethylene-independent petal senescence.

Identification of a NAC transcription factor, EPHEMERAL1, that controls petal senescence in Japanese morning glory

“…Petal senescence of Violet has been shown to be independent of endogenously produced ethylene (Yamada et al ., ; Shinozaki et al ., ; Shibuya, ), and this was confirmed by treatment with 1–MCP, an ethylene action inhibitor, in this study. The abundance of EPH1 transcripts increased as the petals senesced, independently of ethylene signal, suggesting that EPH1 is regulated developmentally in an age‐dependent manner.…”

“…Although petal senescence is regulated independently of endogenous ethylene during naturally occurring senescence in Violet, senescence is known to be accelerated by exogenous ethylene treatment (Yamada et al ., ; Shibuya, ). Similar phenomena have been reported during the senescence of Mirabilis jalapa flowers (Xu et al ., ).…”

“…Furthermore, it has been shown that treatment with 1–methylcyclopropene (1–MCP), a specific inhibitor of ethylene perception, does not delay petal senescence in Violet (Yamada et al ., ). Based on these observations, petal senescence of Violet is considered to be regulated independently of endogenous ethylene (Yamada et al ., ; Shinozaki et al ., ; Shibuya, ). Violet shows distinct PCD symptoms, including DNA degradation and chromatin condensation during petal senescence (Yamada et al ., ).…”

“…Petal senescence, or programmed cell death (PCD) in petals, is a developmentally regulated and genetically programmed process (Rogers, , ; van Doorn and Woltering, ). The phytohormone ethylene is known to accelerate petal senescence in some plant species but to have little effect in other plant species (van Doorn, ; Shibuya, ). Despite long‐standing interest in the regulatory pathways for PCD in petal senescence that are developmentally controlled in an age‐dependent manner regardless of the ethylene signal, little is known of the regulators that control the pathways.…”

Difference in Flower Longevity and Endogenous Ethylene Production of <i>Portulaca umbraticola</i> Cultivars

“…In Ipomoea nil 'Violet', exogenously applied ethylene accelerated petal senescence; however, AVG and 1-MCP did not delay senescence (Yamada et al, 2006). On the basis of these observations, petal senescence of I. nil 'Violet' is considered to be regulated independently of endogenous ethylene (Shibuya, 2012;Yamada et al, 2006). Although the senescence of both P. umbraticola cultivars and I. nil 'Violet' is accelerated by exogenous ethylene, their senescence pathways tend to differ since they respond differently to ethylene action and ethylene biosynthesis inhibitors.…”