AOBPreview published online on July 28, 2006
Annals of Botany, doi:10.1093/aob/mcl149
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1 Institute of Environmental Biotechnology, National Agricultural Research Foundation, Lakonikis 87, 24 100 Kalamata, Greece
* To whom correspondence should be addressed.
• Background and Aims Recent studies have shown that certain composts may trigger indirect defence mechanisms by sensitizing the plant to create an increased state of resistance, similar to systemic acquired resistance. In this study, the capacity of a disease-suppressive compost to alter the expression pattern of certain pathogenesis-related (PR) genes in the root system of tomato plants (Solanum lycopersicum) provided the opportunity to study their cellular expression pattern and to investigate putative roles of these genes in the mechanisms of plant defence. • Methods Employing the reverse transcription-polymerase chain reaction (RT-PCR) and in situ RNA:RNA hybridization techniques, the accumulation and distribution of the transcripts of the differentially expressed PR genes were examined in plants grown on compost and compared with those of control plants grown on peat. • Key Results Elevated levels of expression of the pathogenesis-related genes PR-1, PR-5 and P69/PR-7 were detected in the roots of tomato plants grown on the compost. A clearly distinguished spatial induction pattern was observed for these PR genes: PR-1 transcripts were almost exclusively detected in the pericycle cells surrounding the root stele of the main and lateral roots; PR-5 transcripts were present in the phloem of the root and stem tissues; and the accumulation and distribution of PR-7 transcripts was detected in discrete groups of cells that appeared sporadically in both the parenchyma and vascular system of the root, suggesting that the gene is not expressed in a tissue-specific manner. In addition, a novel cDNA clone was isolated (P69G), which probably encodes a new tomato P69 isoform. • Conclusions This study provides evidence that a supressive compost is able to elicit consistent and increased expression of certain PR genes in the roots of tomato plants, even in the absence of any pathogen. The in situ localization studies reveal expression patterns which are in accordance with the presence of protein or with the putative roles of the respective encoded proteins. The expression of the PR genes may be triggered by the microflora of the compost or could be associated with abiotic factors of the compost.
Received April 4, 2006
Revised May 10, 2006
Accepted May 31, 2006
Article
Cytological and Other Aspects of Pathogenesis-related Gene Expression in Tomato Plants Grown on a Suppressive Compost
NEKTARIOS KAVROULAKIS 1 *, KALLIOPE K. PAPADOPOULOU 2, SPYRIDON NTOUGIAS 1, GEORGIOS I. ZERVAKIS 1, and CONSTANTINOS EHALIOTIS 3
2 Institute of Environmental Biotechnology, National Agricultural Research Foundation, Lakonikis 87, 24 100 Kalamata, Greece; Present address: Department of Biochemistry and Biotechnology, University of Thessaly, Ploutonos 26 and Aiolou, 41221 Larissa, Greece
3 Agricultural University of Athens, Soils and Agricultural Chemistry Laboratory, Department of Natural Resources and Agricultural Engineering, Athens, Greece
NEKTARIOS KAVROULAKIS, E-mail: nkavroulakis{at}in.gr
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