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Comparative transcript profiling by cDNA-AFLP reveals similar patterns of Avr4/Cf-4- and Avr9/Cf-9-dependent defence gene expression
- HONG, WEI, XU, YOU-PING, ZHENG, ZHONG, CAO, JIA-SHU, CAI, XIN-ZHONG
- Molecular plant pathology 2007 v.8 no.4 pp. 515-527
- tomatoes, proteins, cell death, seedlings, signal transduction, environmental factors, gene expression, genes, oxidation, photosynthesis, gene expression regulation, hypersensitive response, pathogens, Passalora fulva
- Tomato Cf genes confer resistance to the fungal pathogen Cladosporium fulvum. Although the Cf-4 and Cf-9 proteins are very similar, the Cf-4- and Cf-9-dependent hypersensitive responses (HRs) are distinct in cell death pattern, intensity and sensitivity to environmental conditions. To investigate the mechanism leading to these differences, comparative transcript profiling of Avr4/Cf-4- and Avr9/Cf-9-dependent defence gene expression was performed. To do this, cDNA-AFLP analysis was conducted on Avr/Cf tomato seedlings undergoing early HR. Both Avr4/Cf-4 and Avr9/Cf-9 signalling elicited the same spectrum of genes, referred to here as Avr/Cf-elicited (ACE) genes. Of approximately 25 000 transcript-derived fragments (TDFs), 367 (1.5%) showed significant differential expression between HR⁺ and HR⁻ seedlings (either Avr4/Cf-4- or Avr9/Cf-9-dependent). However, 42.8% of the ACE TDFs (157/367 in total) showed quantitatively different expression in the two types of HR⁺ seedlings. The majority of these (135/157, 86.0%) displayed significantly greater differential expression (either induced or repressed) in Avr4/Cf-4 HR⁺ seedlings than in Avr9/Cf-9 HR⁺ seedlings. Our results are consistent with the previous observation that Avr4/Cf-4-dependent HR is more severe than Avr9/Cf-9-dependent HR, and indicate that the distinction between Avr4/Cf-4- and Avr9/Cf-9-dependent HR is most probably a result of events upstream of the defence responses. Sequencing of 189 ACE fragments identified genes associated with: defence and resistance (33.3%), signal transduction (7.4%), HR and cell death (5.3%), transcriptional regulation and post-transcriptional modification (4.3%). Expression data revealed that defence response, respiration and biological oxidation are strongly induced while photosynthesis is severely repressed in the HR⁺ seedlings.