Characterization of defense signaling pathways of brassica napus and brassica carinata in response to sclerotinia sclerotiorum challenge (original) (raw)

2010, Plant Molecular Biology Reporter

Canola (Brassica napus L.) is an agriculturally and economically important crop in Canada, and its growth and yield are frequently influenced by fungal pathogens. Sclerotinia sclerotiorum is among those fungal pathogens and causes stem rot disease in B. napus whereas it has been reported that Brassica carinata is moderately tolerant to S. sclerotiorum. Jasmonic acid/ethylene (JA/ET) and salicylic acid (SA) are phytohormones that are known to be involved in plant disease responses. To investigate the defense signaling cascades involved in the interaction of B. napus and B. carinata with S. sclerotiorum, we examined the expression of five orthologs of B. napus genes involved in JA/ET or SA signaling pathways using quantitative RT-PCR. Our results indicated that there are differences in the timing of JA/ET and SA signaling pathways between B. napus and B. carinata. Our results in these two Brassica species also support previous observations that necrotrophic pathogens trigger JA/ET signaling in response to infection. Finally, we observed that transgenic canola expressing 1aminocyclopropane-1-carboxylate-deaminase producing low levels of ET was relatively more susceptible to S. sclerotiorum than its wild-type counterpart, suggesting that ET inhibits S. sclerotiorum-induced symptom development. Keywords Brassica. Sclerotinia sclerotiorum. Signaling pathway (ET), salicylic acid (SA), or reactive oxygen species (Kunkel and Brooks 2002). Signaling pathways, mediated by JA/ET and SA, are important components of plant defense systems (Dong 1998; Feys and Parker 2000; Martinez et al. 2001; McDowell and Dangl 2000). They are regulated and can act independently, synergistically, or antagonistically, which depends on the system between host/pathogens and are discussed below (Glazebrook 2005; Kachroo and Kachroo 2007). JA and its derivate methyl jasmonate (MeJA) are signaling molecules important for initiating and/or maintaining developmental processes and defense responses in various plants (Clarke et al. 2001; van der Fits et al. 2000). In Arabidopsis, as revealed by microarray analysis, five out Both Muhammad Rahman and Yue Liang contributed equally.