Tomato Transcriptional Changes in Response toClavibacter michiganensissubsp.michiganensisReveal a Role for Ethylene in Disease Development  

Abstract

Clavibacter michiganensis subsp. michiganensis (Cmm) is a gram-positive actinomycete, causing bacterial wilt and canker disease in tomato (Solanum lycopersicum). Host responses to gram-positive bacteria and molecular mechanisms associated with the development of disease symptoms caused by Cmm in tomato are largely unexplored. To investigate plant responses activated during this compatible interaction, we used microarray analysis to monitor changes in host gene expression during disease development. This analysis was performed at 4 d postinoculation, when bacteria were actively multiplying and no wilt symptoms were yet visible; and at 8 d postinoculation, when bacterial growth approached saturation and typical wilt symptoms were observed. Of the 9,254 tomato genes represented on the array, 122 were differentially expressed in Cmminfected plants, compared with mock-inoculated plants. Functional classification of Cmm-responsive genes revealed that Cmm activated typical basal defense responses in the host, including induction of defense-related genes, production and scavenging of free oxygen radicals, enhanced protein turnover, and hormone synthesis. Cmm infection also induced a subset of host genes involved in ethylene biosynthesis and response. After inoculation with Cmm, Never ripe (Nr) mutant plants, impaired in ethylene perception, and transgenic plants with reduced ethylene synthesis showed significant delay in the appearance of wilt symptoms, compared with wild-type plants. The retarded wilting in Nr plants was a specific effect of ethylene insensitivity, and was not due to altered expression of defense-related genes, reduced bacterial populations, or decreased ethylene synthesis. Taken together, our results indicate that host-derived ethylene plays an important role in regulation of the tomato susceptible response to Cmm.

Over-expression of snakin-2 and extensin-like protein genes restricts pathogen invasiveness and enhances tolerance to Clavibacter michiganensis subsp. michiganensis in transgenic tomato (Solanum lycopersicum)

“…Interestingly, gene expression was down-regulated after inoculation with bacterial pathogens Ralstonia solanacearum and Erwinia chrysanthemi (Berrocal-Lobo et al 2002). A similar observation was documented from our previous study where the tomato SN2 gene was down-regulated less than twofold upon Cmm infection (Balaji et al 2008). Down-regulation of defense genes by some pathogens has been suggested as a mechanism to overcome plant defense (Jakobek et al 1993).…”

Effects of plant age on disease development and virulence of Clavibacter michiganensis subsp. michiganensis on tomato

“…tomato is correlated with the intercellular level of salicylic acid (Carviel et al, 2009). Transcriptional analysis of young tomato plants in response to Cmm infection revealed that a subset of host genes is highly induced, including defence-related genes, production and scavenging of free oxygen radicals and hormone synthesis (Balaji et al, 2008). It might be hypothesized that in older tomato plants, enhanced host defence responses lead to an increased ARR response to Cmm.…”

Pleiotropic Phenotypes of the sticky peel Mutant Provide New Insight into the Role of CUTIN DEFICIENT2 in Epidermal Cell Function in Tomato

“…The PCR reactions were performed with FAST SYBR master mix, 23 (ABI, http://www.appliedbiosystems.com) in a 25 mL volume using an Applied Biosystems StepOnePlus real-time PCR system (ABI) with the following cycling program: 10 min at 95°C, 15 s at 95°C followed by 40 cycles of 1 min at 60°C, 15 s at 95°C, and 1 min at 60°C. The comparative DDCT method was performed according to Balaji et al (2008).…”