Identification and transcriptional analysis of genes involved in Bacillus cereus-induced systemic resistance in Lilium

Bacillus cereus C1L was demonstrated to induce systemic resistance in Lilium formosanum against leaf blight caused by Botrytis elliptica. Suppression subtractive hybridization library of L. formosanum triggered by B. cereus C1L were screened and 3 differentially expressed genes were identified. Based on sequence analysis, these genes encoding putative glycine-rich protein, metallothionein-like protein, and PsbR protein of photosystem 2, were designated LfGRP1, LfMT1, and LfPsbR, respectively. The results of Northern blot analysis showed that expressions of LfGRP1, LfMT1 and LfPsbR increased in response to B. elliptica infection. On the other hand, expression of LfMT1 increased but expressions of LfGRP1 and LfPsbR decreased when the rhizosphere of L. formosanum was drenched with suspension of B. cereus C1L with or without subsequent challenge with B. elliptica on lily leaves. Similar expression profiles of homologues of LfGRP1, LfMT1, and LfPsbR (named LsGRP1, LsMT1, and LsPsbR, respectively) were presented in Lilium oriental hybrid Star Gazer. In addition, application of the photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, on the leaves reduced disease severity and expressions of LsGRP1 and LsPsbR just as that in response to B. cereus C1L treatment.