Publikationsserver der RWTH Aachen University
Untersuchungen zur Funktion einer Lipoxygenase in der induzierten Resistenz bei Reis
Abstract
dc:descriptionThe phenomenon of systemic acquired resistance (SAR) can be induced by the application of chemical substances like BTH, which is considered as a functional analogue of salicylic acid. Acquired resistance in plants leads to a long-lasting protection against a broad range of pathogens. However, in case of chemically-induced resistance the systemic propagation of protection observed may be due to the systemic spread of the inducing agent itself. The details of how chemically-induced crop plants respond to pathogens is not well understood. Treatment of monocotyledonous plants with chemical resistance inducers leads to expression of several genes some with unknown function. Some of them are referred to as "marker-genes" because of their expression during the onset of the chemically induced resistance response. A cDNA was cloned, whose corresponding transcripts accumulated after treatment of rice plants with chemical resistance inducers but not after infection. This cDNA was referred to as RCI1 ("rice chemically induced cDNA1") and it encodes a lipoxygenase. A strong correlation was demonstrated in rice between the accumulation of RCI1-transcripts and the occurence of resistance after treatment with chemical inducers. RCI1 might orchestrate the onset of this type of resistance. Biochemical analysis was carried out to investigate the positional specifity of the RCI1-lipoxygenase. Finally, the classification of RCI1 as a member of the 13-LOX family was confirmed. Free fatty acids were identificated as the prefered substrate for RCI1. In the genome of rice plants only a single gene seems to hybridise with an RCI1-probe under stringent conditions as shown by Southern analysis. Overexpression of a fusion-protein, consisting of a putative N-terminal transitpeptide of RCI1 and the green fluorescent protein (GFP) as a reporter, was localised subcellularly in chloroplasts. Furthermore, RCI1 was overexpressed in rice leaves to investigate the possible function of RCI1 in chemically-induced resistance of rice. In this transient assay RCI1-overexpression led to the accumulation of PR1-specific transcripts. Transformation with an RCI1-construct encoding for an enzyme with a deletion in the catalytical domain did not show any accumulation of PR1-specific transcripts. Therefore, it was concluded that enzymatic activity of RCI1 is necessary for the induction of PR1-transcription. The transformation of rice leaves with a construct for overexpression of RCI1 without the N-terminal chloroplast targeting signal also failed to induce PR1-transcription. However, the corresponding recombinant protein showed reduced lipoxygenase activity. Therefore, it remains uncertain whether RCI1-expression in the chloroplasts is necessary for the induction of PR1-transcription. In addition 13(S)-HOT, an oxylipin from the lipoxygenase pathway was shown to induce accumulation of PR1-transcripts. These results may indicate that RCI1 is a component of the signaltransduction pathway of the chemically-induced acquired resistance response in rice.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2004
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Zabbai, Frauke
- Contributors dc:contributor
-
- Slusarenko, Alan
Subjects
dc:subject × 8Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger
Identifiers
dc:identifier.*- OAI identifier oai:identifier
- oai:publications.rwth-aachen.de:61997