Studies on Bacillus cereus C1L-induced systemic resistance against Botrytis elliptica in Lilium
Date Issued
2008
Date
2008
Author(s)
Liu, Yi-Hung
Abstract
Application of Bacillus cereus C1L suspension in the rhizosphere of Lilium formosanum and lily cv. Star Gazer to reduce gray mold severity has been demonstrated. In this dissertation, the mechanism of induced systemic resistance (ISR) was approached to figure out the signaling pathway involved. Firstly, differentially expressed genes in strain C1L-treated L. formosanum were identified to be LfGRP1, LfMT1, and LfPsbR, by the use of suppression subtractive hybridization method. When L. formosanum was treated with strain C1L, LfMT1 was up-regulated. However, LfGRP1 and LfPsbR were down-regulated. The expression patterns of the 3 homologues in oriental lily cv. Star Gazer were identical to those of LfGRP1, LfMT1 and LfPsbR. When using ethylene and methyl jasmonate to treat lily cv. Star Gazer, LsGRP1 and LsPsbR were up-regulated. On the contrary, these genes were down-regulated by the treatment of abscissic acid (ABA), indicating that ABA signaling pathway is involved in the systemic resistance induced by strain C1L. When ‘Stra Gazer’ lily plants were treated with strain C1L 24 hours before inoculation with B. elliptica, accumulation of hydrogen peroxide and cell death in the leaves was suppressed as compared to those exhibited in the plant singly inoculated with B. elliptica. The peroxidase activity was not increased in the leaves inoculated with B. elliptica post strain C1L treatment, unlike that inoculated with B. elliptica singly. On the other hand, strain C1L induced early expression of LpGlu1 (β-1,3-glucanase) in response to B. elliptica infection post strain C1L treatment as compared to that inoculated with B. elliptica singly. In order to dissect the mechanism of ISR activated by strain C1L, cDNA-AFLP was analyzed and 104 cDNA clones representative of differentially expressed genes of lily were obtained. Expressions of selected genes were analyzed by semi-quantitative reverse-transcription polymerase chain reaction. The results showed that strain C1L could induce systemic resistance via calcium ion signaling pathway and ABA signaling pathway, followed by anti-oxidative response. Additionally, strain C1L induced expression of glutamate synthase of lily which might decrease cellular toxicity caused by B. elliptica and therefore reduced the disease severity.
Subjects
Rhizobacteria
induced systemic resistance
hydrogen peroxide
plant cell death
antioxidation
abscisic acid
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