Sucrose prevents up-regulation of senescence-associated genes in carnation petals

Abstract

cDNA microarrays were used to characterize senescence-associated gene expression in petals of cut carnation (Dianthus caryophyllus) flowers, sampled from anthesis to the first senescence symptoms. The population of PCR fragments spotted on these microarrays was enriched for flower-specific and senescence-specific genes, using subtractive hybridization. About 90% of the transcripts showed a large increase in quantity, approximately 25% transiently, and about 65% throughout the 7 d experiment. Treatment with silver thiosulphate (STS), which blocks the ethylene receptor and prevented the normal senescence symptoms, prevented the up-regulation of almost all of these genes. Sucrose treatment also considerably delayed visible senescence. Its effect on gene expression was very similar to that of STS, suggesting that soluble sugars act as a repressor of ethylene signal transduction. Two fragments that encoded a carnation EIN3-like (EIL) protein were isolated, some of which are key transcription factors that control ethylene response genes. One of these (Dc-EIL3) was up-regulated during senescence. Its up-regulation was delayed by STS and prevented by sucrose. Sucrose, therefore, seems to repress ethylene signalling, in part, by preventing up-regulation of Dc-EIL3. Some other transcription factors displayed an early increase in transcript abundance: a MYB-like DNA binding protein, a MYC protein, a MADS-box factor, and a zinc finger protein. Genes suggesting a role in senescence of hormones other than ethylene encoded an Aux/IAA protein, which regulate transcription of auxin-induced genes, and a cytokinin oxidase/dehydrogenase, which degrades cytokinin. Taken together, the results suggest a master switch during senescence, controlling the co-ordinated up-regulation of numerous ethylene response genes. Dc-EIL3 might be (part of) this master switch.

An Ethylene-Induced Regulatory Module Delays Flower Senescence by Regulating Cytokinin Content

“…Accordingly, it has been reported that rose varieties with long flower longevity contain higher levels of CTKs than those with shorter lived flowers (Mayak and Halevy, 1970), and CTK application has been shown to delay flower senescence in several plant species, including carnation (Dianthus caryophyllus), petunia (Petunia hybrida), and rose (Mayak and Halevy, 1970;Mor et al, 1983;Taverner et al, 1999). Conversely, an increase in transcript abundance of two genes encoding CTK oxidase/dehydrogenase during carnation petal senescence accelerated CTK degradation and promoted corolla senescence (Hoeberichts et al, 2007).…”

Flower senescence: some molecular aspects

“…Genes associated with senescence have been isolated from a number of flowers exhibiting ethylene-sensitive, ethylene-insensitive or intermediate pattern of senescence (Lawton et al 1990;Hunter et al 2002;van Doorn et al 2003;Breeze et al 2004;Hoeberichts et al 2007;Xu et al 2007a). A large population of genes associated with flower senescence have been identified and isolated in Narcissus, Alstroemeria, Iris, Mirabilis, etc.…”

“…The recently characterized RbCP1 gene from rose petals has been reported to encode a putative 37 kDa cysteine protease (357 amino acids) belonging to a typical papain type protease (having the presence of the CIA peptidase domain and the eRFNIN motif; Tripathi et al 2009). Similarly in carnation, one of the identified cysteine protease gene has been found to display homology to a tobacco vacuolar processing enzyme (vPe: a caspase-like protein associated with senescence and virus-induced hypersensitive cell death: (Hatsugai et al 2006;Hoeberichts et al 2007). However, no cysteine protease has been isolated from senescing Mirabilis Jalapa flowers (Xu et al 2007a).…”

“…In addition to cysteine endopeptidases, the genes encoding ubiquitin involved in proteasomal protein degradation have been identified from various flower systems, e.g., partial cDNA of ubiquitin (ALSUQ1) from Alstroemeria, a gene encoding polyubiquitin (an essential element in ubiquitin pathway) form M. jalapa, and transcripts from carnation homologous to genes encoding the components of the 26S proteosome machinery (RPT6, RPN2), a Ring finger protein and a U-box containing protein (wagstaff et al 2002;Hoeberichts et al 2007;Xu et al 2007a). The identification and upregulation of a Ring Zinc finger ankyrin protein (MjXB3) have also been reported from senescing M. jalapa flowers which share similarity to XBAT31 and XBAT32 of A. thaliana and Glycine max, respectively.…”

“…The transcripts encoding a range of transcription factors have been isolated and found to be differentially regulated during development and senescence in various flower systems (Table 5), e.g., a homeodomain protein (a class of proteins generally representing transcription factors), MYBlike DNA-binding protein, MYC protein and Zinc-finger protein from Dianthus and Mirabilis, MADS Box genes from carnation, Iris and Arabidopsis, NAC domain transcription factors and CeBP "Carnation ethylene-responsive element binding protein" (waki et al 2001;Fang and Fernandez 2002;van Doorn et al 2003;Hoeberichts et al 2007;Iordachescu et al 2009;Balazadeh et al 2010). The Iris MADS box gene has been found to share 51 % identity with RIN (a MADS-box factor involved in developmental control of fruit ripening in tomato; vrebalov et al 2002) and that the corresponding translated fragment from carnation shares 34 % identity with tomato RIN and 55 % identity with the Arabidopsis pistillate protein (Hoeberichts et al 2007).…”