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A compatible interaction of Alternaria brassicicola with Arabidopsis thaliana ecotype DiG: evidence for a specific transcriptional signature.

Mukherjee AK, Lev S, Gepstein S, Horwitz BA - BMC Plant Biol. (2009)

Bottom Line: PR1, and a monooxygenase gene identified in this study, MO1, are preferentially up-regulated in the compatible interaction.In contrast, GLIP1, which encodes a secreted lipase, and DIOX1, a pathogen-response related dioxygenase, are preferentially up-regulated in the incompatible interaction.The results show that DiG is not only more susceptible, but demonstrate that its interaction with A. brassicicola has a specific transcriptional signature.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, Israel Institute of Technology, Technion, Haifa, Israel. titirtua@gmail.com

ABSTRACT

Background: The interaction of Arabidopsis with Alternaria brassicicola provides a model for disease caused by necrotrophs, but a drawback has been the lack of a compatible pathosystem. Infection of most ecotypes, including the widely-studied line Col-0, with this pathogen generally leads to a lesion that does not expand beyond the inoculated area. This study examines an ecotype, Dijon G (DiG), which is considered sensitive to A. brassicicola.

Results: We show that the interaction has the characteristics of a compatible one, with expanding rather than limited lesions. To ask whether DiG is merely more sensitive to the pathogen or, rather, interacts in distinct manner, we identified genes whose regulation differs between Col-0 and DiG challenged with A. brassicicola. Suppression subtractive hybridization was used to identify differentially expressed genes, and their expression was verified using semi-quantitative PCR. We also tested a set of known defense-related genes for differential regulation in the two plant-pathogen interactions. Several known pathogenesis-related (PR) genes are up-regulated in both interactions. PR1, and a monooxygenase gene identified in this study, MO1, are preferentially up-regulated in the compatible interaction. In contrast, GLIP1, which encodes a secreted lipase, and DIOX1, a pathogen-response related dioxygenase, are preferentially up-regulated in the incompatible interaction.

Conclusion: The results show that DiG is not only more susceptible, but demonstrate that its interaction with A. brassicicola has a specific transcriptional signature.

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Related in: MedlinePlus

Semi-quantitative RT PCR analysis of transcript levels of selected genes. - and + indicate samples from control and inoculated intact plants, respectively. RNA was isolated by harvesting the entire leaf at 72 h after inoculation. Duplicate lanes indicate two independent experiments on different sets of plants; the number of amplification cycles is indicated at the right.
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Figure 2: Semi-quantitative RT PCR analysis of transcript levels of selected genes. - and + indicate samples from control and inoculated intact plants, respectively. RNA was isolated by harvesting the entire leaf at 72 h after inoculation. Duplicate lanes indicate two independent experiments on different sets of plants; the number of amplification cycles is indicated at the right.

Mentions: Semi-quantitative RT-PCR analysis of the abundance of the corresponding transcripts is shown in Fig. 2. An actin gene (ACT2), a ubiquitin-conjugating enzyme gene (UBC) and cap-binding protein 20 (CBP20) were used as "housekeeping" genes (Table 2). The false-positive library clones also serve as additional controls for overall efficiency of the RT PCR procedure (Fig. 2). The fold-induction by infection relative to Col-0 is shown in Fig. 3. The transcripts detected by three of the test primer pairs: PDIOX, RD21A and MO1F (Table 2) showed clearly differential expression in the compatible interaction. The transcripts corresponding to GS, MDH and PEX42 did not, although even a slight differential expression might have led to inclusion in the library. The transcript corresponding to primer pair PDIOX is more highly expressed in the incompatible interaction. The relatively low proportion of differential SSH clones in the test set (3 out of 9) may reflect the choice of test primer pairs, which included only genes that were not previously annotated as pathogen-response dependent (Table 1). Among the candidate genes tested, PR1, PR3, PR4 and PDF1.2 were strongly up-regulated in both Col-0 and DiG interactions. The transcript levels of these genes were very low in uninfected plants, with the exception of PR1 (Fig. 2), so that induction ratios could not be estimated. Transcripts of the other candidates (Table 1), including three ethylene-response related genes, were not detectable under these conditions and it can be inferred that they are not strongly induced. The infection-related lipase gene GLIP1 is expressed at a higher level (about 4-fold) in the incompatible than in the compatible interaction, while PR1 is expressed about 4-fold higher in the compatible than in the incompatible interaction.


A compatible interaction of Alternaria brassicicola with Arabidopsis thaliana ecotype DiG: evidence for a specific transcriptional signature.

Mukherjee AK, Lev S, Gepstein S, Horwitz BA - BMC Plant Biol. (2009)

Semi-quantitative RT PCR analysis of transcript levels of selected genes. - and + indicate samples from control and inoculated intact plants, respectively. RNA was isolated by harvesting the entire leaf at 72 h after inoculation. Duplicate lanes indicate two independent experiments on different sets of plants; the number of amplification cycles is indicated at the right.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2664814&req=5

Figure 2: Semi-quantitative RT PCR analysis of transcript levels of selected genes. - and + indicate samples from control and inoculated intact plants, respectively. RNA was isolated by harvesting the entire leaf at 72 h after inoculation. Duplicate lanes indicate two independent experiments on different sets of plants; the number of amplification cycles is indicated at the right.
Mentions: Semi-quantitative RT-PCR analysis of the abundance of the corresponding transcripts is shown in Fig. 2. An actin gene (ACT2), a ubiquitin-conjugating enzyme gene (UBC) and cap-binding protein 20 (CBP20) were used as "housekeeping" genes (Table 2). The false-positive library clones also serve as additional controls for overall efficiency of the RT PCR procedure (Fig. 2). The fold-induction by infection relative to Col-0 is shown in Fig. 3. The transcripts detected by three of the test primer pairs: PDIOX, RD21A and MO1F (Table 2) showed clearly differential expression in the compatible interaction. The transcripts corresponding to GS, MDH and PEX42 did not, although even a slight differential expression might have led to inclusion in the library. The transcript corresponding to primer pair PDIOX is more highly expressed in the incompatible interaction. The relatively low proportion of differential SSH clones in the test set (3 out of 9) may reflect the choice of test primer pairs, which included only genes that were not previously annotated as pathogen-response dependent (Table 1). Among the candidate genes tested, PR1, PR3, PR4 and PDF1.2 were strongly up-regulated in both Col-0 and DiG interactions. The transcript levels of these genes were very low in uninfected plants, with the exception of PR1 (Fig. 2), so that induction ratios could not be estimated. Transcripts of the other candidates (Table 1), including three ethylene-response related genes, were not detectable under these conditions and it can be inferred that they are not strongly induced. The infection-related lipase gene GLIP1 is expressed at a higher level (about 4-fold) in the incompatible than in the compatible interaction, while PR1 is expressed about 4-fold higher in the compatible than in the incompatible interaction.

Bottom Line: PR1, and a monooxygenase gene identified in this study, MO1, are preferentially up-regulated in the compatible interaction.In contrast, GLIP1, which encodes a secreted lipase, and DIOX1, a pathogen-response related dioxygenase, are preferentially up-regulated in the incompatible interaction.The results show that DiG is not only more susceptible, but demonstrate that its interaction with A. brassicicola has a specific transcriptional signature.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, Israel Institute of Technology, Technion, Haifa, Israel. titirtua@gmail.com

ABSTRACT

Background: The interaction of Arabidopsis with Alternaria brassicicola provides a model for disease caused by necrotrophs, but a drawback has been the lack of a compatible pathosystem. Infection of most ecotypes, including the widely-studied line Col-0, with this pathogen generally leads to a lesion that does not expand beyond the inoculated area. This study examines an ecotype, Dijon G (DiG), which is considered sensitive to A. brassicicola.

Results: We show that the interaction has the characteristics of a compatible one, with expanding rather than limited lesions. To ask whether DiG is merely more sensitive to the pathogen or, rather, interacts in distinct manner, we identified genes whose regulation differs between Col-0 and DiG challenged with A. brassicicola. Suppression subtractive hybridization was used to identify differentially expressed genes, and their expression was verified using semi-quantitative PCR. We also tested a set of known defense-related genes for differential regulation in the two plant-pathogen interactions. Several known pathogenesis-related (PR) genes are up-regulated in both interactions. PR1, and a monooxygenase gene identified in this study, MO1, are preferentially up-regulated in the compatible interaction. In contrast, GLIP1, which encodes a secreted lipase, and DIOX1, a pathogen-response related dioxygenase, are preferentially up-regulated in the incompatible interaction.

Conclusion: The results show that DiG is not only more susceptible, but demonstrate that its interaction with A. brassicicola has a specific transcriptional signature.

Show MeSH
Related in: MedlinePlus