Defining the mechanisms underlying resistance to stem rot disease (S. sclerotiorum) in Brassica napus

摘要

Sclerotinia sclerotiorum is a necrotrophic fungal pathogen capable of infecting a wide range of plants, including Brassica napus. Genomics approaches were employed to gain insight into the mechanisms responsible for resistance in the Chinese B.napus cultivar, Zhong You 821(ZY821). Doubled haploid (DH) lines were created from crosses between ZY821 and susceptible B. napus lines. 800 ESTs were generated from each of two subtractive cDNA libraries that were designed to enrich for genes expressed in infected but not in uninfected ZY821 stems and in resistant but not in susceptible DH lines. A total of 58 and 120 uni-genes were identified among the infected vs uninfected and resistant vs susceptible ESTs, respectively. The genes induced in response to infection in ZY821 included many well-characterized anti-fungal proteins such as a hevein-like protein, three chitinases, β-1,3 glucanase, PR-1 and PR-5 as well as several regulatory proteins. The uni-gene set unique to the resistant DH lines included 36 proteins with no ascribed function (two types were highly prevalent) as well as PR1 and a hevein-like protein. Since the subtractive library procedure eliminates transcripts having even some degree of similarity, members of multi-gene families (such as transcription factors) are often eliminated or under-represented. To overcome this limitation, we used a 16,000 feature B.napus oligonucleotide micro-array designed to be gene-specific. A time course study was conducted to monitor gene expression profiles in infected ZY821 stems during the very early (6 h) to later (72 h) stages of the infection. We found that three WRKY-like transcription factors were induced (up to 14 times) and these are being further characterized for their contribution to resistance.