Abstract
BackgroundThe phytohormone ethylene plays a central role in development and senescence of climacteric flowers. In ornamental plant production, ethylene sensitive plants are usually protected against negative effects of ethylene by application of chemical inhibitors. In Campanula, flowers are sensitive to even minute concentrations of ethylene.ResultsMonitoring flower longevity in three Campanula species revealed C. portenschlagiana (Cp) as ethylene sensitive, C. formanekiana (Cf) with intermediate sensitivity and C. medium (Cm) as ethylene insensitive. We identified key elements in ethylene signal transduction, specifically in Ethylene Response Sensor 2 (ERS2), Constitutive Triple Response 1 (CTR1) and Ethylene Insensitive 3- Like 1 and 2 (EIL1 and EIL2) homologous. Transcripts of ERS2, CTR1 and EIL1 were constitutively expressed in all species both throughout flower development and in response to ethylene. In contrast, EIL2 was found only in Cf and Cm. We identified a natural mutation in Cmeil2 causing a frameshift which resulted in difference in expression levels of EIL2, with more than 100-fold change between Cf and Cm in young flowers.ConclusionsThis study shows that the naturally occurring 7 bp frameshift discovered in Cmeil2, a key gene in the ethylene signaling pathway, correlates with ethylene insensitivity in flowers. We suggest that transfer of the eil2 mutation to other plant species will provide a novel tool to engineer ethylene insensitive flowers.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0786-4) contains supplementary material, which is available to authorized users.
Highlights
The phytohormone ethylene plays a central role in development and senescence of climacteric flowers
Campanula sensitivity to ethylene To understand the physiological variation in ethylene sensitivity among Campanula species, we used ethylene exposure tests in a postharvest environment
Less pronounced ethylene sensitivity was found in C. formanekiana (Cf) where 26 % of old flowers wilted in response to 72 h of 0.05 μL · L−1 ethylene as opposed to 100 % of old C. portenschlagiana (Cp) flowers
Summary
The phytohormone ethylene plays a central role in development and senescence of climacteric flowers. Ethylene is a gaseous phytohormone involved in regulating processes of horticultural importance encompassing flower development, fruit ripening, abscission and leaf and flower senescence [1]. In Arabidopsis, receptor proteins comprising EThylene Response 1 (ETR1) and Ethylene Response Sensor 1 (ERS1) or ETR2, ERS2 and Ethylene INsensitive 4 (EIN4) have been characterised. They differ by the functionality of their kinase domains [4,5,6]. Ethylene receptors exist as dimers and physically interact with the negative regulator Constitutive Triple Response 1 (CTR1) [7]. The kinase activity of CTR1 is directed towards the C-
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