Abstract
Flowers are complex systems whose vegetative and sexual structures initiate and die in a synchronous manner. The rapidity of this process varies widely in flowers, with some lasting for months while others such as Hibiscus rosa-sinensis survive for only a day. The genetic regulation underlying these differences is unclear. To identify key genes and pathways that coordinate floral organ senescence of ephemeral flowers, we identified transcripts in H. rosa-sinensis floral organs by 454 sequencing. During development, 2053 transcripts increased and 2135 decreased significantly in abundance. The senescence of the flower was associated with increased abundance of many hydrolytic genes, including aspartic and cysteine proteases, vacuolar processing enzymes, and nucleases. Pathway analysis suggested that transcripts altering significantly in abundance were enriched in functions related to cell wall-, aquaporin-, light/circadian clock-, autophagy-, and calcium-related genes. Finding enrichment in light/circadian clock-related genes fits well with the observation that hibiscus floral development is highly synchronized with light and the hypothesis that ageing/senescence of the flower is orchestrated by a molecular clock. Further study of these genes will provide novel insight into how the molecular clock is able to regulate the timing of programmed cell death in tissues.
Highlights
Flowers in the Angiospermae have been shaped over time by natural selection into a diversity of sizes, shapes, and colours
All the flowers that open within a day open and senesce at exactly the same time. This suggests that the circadian clock is an important key regulator of hibiscus flower development
This conclusion is supported by the significant enrichment of lightrelated gene transcripts found in the functional category analysis, and of the phototropin PHOT1 blue light receptor, which was mainly induced during the hibiscus senescence stage in petals and the S-S+S complex
Summary
Flowers in the Angiospermae have been shaped over time by natural selection into a diversity of sizes, shapes, and colours. Just as these visual attributes have been continually influenced by environmental and other selection pressures, so too has the timing and duration of their flowering and the rapidity at which each individual flower initiates and senesces. This can be rapid, following pollination, and is thought to increase the. There are many biochemical and molecular changes that underlie these different senescence responses
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