JXB Advance Access originally published online on May 24, 2007
Journal of Experimental Botany 2007 58(8):2193-2201; doi:10.1093/jxb/erm058
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RESEARCH PAPER |
Genes associated with opening and senescence of Mirabilis jalapa flowers
1Department of Plant Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA
2Crops Pathology and Genetics Research Unit, United States Department of Agriculture, Agricultural Research Service, One Shields Avenue, Davis, CA 95616, USA
* To whom correspondence should be addressed. E-mail: msreid{at}ucdavis.edu
A modest ethylene climacteric accompanies flower senescence in Mirabilis jalapa L., and exogenous ethylene accelerates the process. However, inhibitors of ethylene action and synthesis have little effect on the life-span of these ephemeral flowers. Treatment with 
-amanitin, an inhibitor of DNA-dependent RNA synthesis, substantially delays the onset of senescence. This effect falls linearly between 7 h and 8 h after the start of flower opening. Subtractive hybridization was used to isolate transcripts that were up- and down-regulated during this critical period. Eighty-two up-regulated and 65 down-regulated transcripts were isolated. The genes identified encode homologues of a range of transcription factors, and of proteins involved in protein turnover and degradation. Real-time quantitative RT-PCR was used to examine expression patterns of these genes during flower opening and senescence. Genes that were identified as being down-regulated during senescence showed a common pattern of very high expression during floral opening. These genes included a homologue of CCA1, a ‘clock’ gene identified in Arabidopsis thaliana and an aspartyl protease. Up-regulated genes commonly showed a pattern of increase during the critical period (4–9 h after opening), and some showed very strong up-regulation. For example, the abundance of transcripts encoding a RING zinc finger protein increased >40 000 fold during the critical period.
Key words: Circadian, ethylene, floral senescence, Mirabilis jalapa, senescence-associated genes, transcription factor, ubiquitin ligase
Received 21 December 2006; Revised 1 February 2007 Accepted 15 February 2007
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