Regulation of RNA-dependent RNA polymerase 1 and isochorismate synthase gene expression in Arabidopsis. 2013

Lydia J R Hunter, and Jack H Westwood, and Geraldine Heath, and Keith Macaulay, and Alison G Smith, and Stuart A Macfarlane, and Peter Palukaitis, and John P Carr
Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom.

BACKGROUND RNA-dependent RNA polymerases (RDRs) function in anti-viral silencing in Arabidopsis thaliana and other plants. Salicylic acid (SA), an important defensive signal, increases RDR1 gene expression, suggesting that RDR1 contributes to SA-induced virus resistance. In Nicotiana attenuata RDR1 also regulates plant-insect interactions and is induced by another important signal, jasmonic acid (JA). Despite its importance in defense RDR1 regulation has not been investigated in detail. RESULTS In Arabidopsis, SA-induced RDR1 expression was dependent on 'NON-EXPRESSER OF PATHOGENESIS-RELATED GENES 1', indicating regulation involves the same mechanism controlling many other SA- defense-related genes, including pathogenesis-related 1 (PR1). Isochorismate synthase 1 (ICS1) is required for SA biosynthesis. In defensive signal transduction RDR1 lies downstream of ICS1. However, supplying exogenous SA to ics1-mutant plants did not induce RDR1 or PR1 expression to the same extent as seen in wild type plants. Analysing ICS1 gene expression using transgenic plants expressing ICS1 promoter:reporter gene (β-glucuronidase) constructs and by measuring steady-state ICS1 transcript levels showed that SA positively regulates ICS1. In contrast, ICS2, which is expressed at lower levels than ICS1, is unaffected by SA. The wound-response hormone JA affects expression of Arabidopsis RDR1 but jasmonate-induced expression is independent of CORONATINE-INSENSITIVE 1, which conditions expression of many other JA-responsive genes. Transiently increased RDR1 expression following tobacco mosaic virus inoculation was due to wounding and was not a direct effect of infection. RDR1 gene expression was induced by ethylene and by abscisic acid (an important regulator of drought resistance). However, rdr1-mutant plants showed normal responses to drought. CONCLUSIONS RDR1 is regulated by a much broader range of phytohormones than previously thought, indicating that it plays roles beyond those already suggested in virus resistance and plant-insect interactions. SA positively regulates ICS1.

UI MeSH Term Description Entries
D005030 Ethylenes Derivatives of ethylene, a simple organic gas of biological origin with many industrial and biological use.
D000040 Abscisic Acid Abscission-accelerating plant growth substance isolated from young cotton fruit, leaves of sycamore, birch, and other plants, and from potatoes, lemons, avocados, and other fruits. 2,4-Pentadienoic acid, 5-(1-hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexen-1-yl)-3-methyl-, (S-(Z,E))-,Abscisic Acid Monoammonium Salt, (R)-Isomer,Abscisic Acid, (+,-)-Isomer,Abscisic Acid, (E,E)-(+-)-Isomer,Abscisic Acid, (E,Z)-(+,-)-Isomer,Abscisic Acid, (R)-Isomer,Abscisic Acid, (Z,E)-Isomer,Abscissic Acid,Abscissins
D001483 Base Sequence The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence. DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA
D012324 RNA-Dependent RNA Polymerase An enzyme that catalyses RNA-template-directed extension of the 3'- end of an RNA strand by one nucleotide at a time, and can initiate a chain de novo. (Enzyme Nomenclature, 1992, p293) Nucleoside-Triphosphate:RNA Nucleotidyltransferase (RNA-directed),RNA Replicase,RNA-Dependent RNA Replicase,RNA-Directed RNA Polymerase,RNA Dependent RNA Polymerase,RNA Dependent RNA Replicase,RNA Directed RNA Polymerase,RNA Polymerase, RNA-Dependent,RNA Polymerase, RNA-Directed,RNA Replicase, RNA-Dependent,Replicase, RNA,Replicase, RNA-Dependent RNA
D015971 Gene Expression Regulation, Enzymologic Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in enzyme synthesis. Enzymologic Gene Expression Regulation,Regulation of Gene Expression, Enzymologic,Regulation, Gene Expression, Enzymologic
D017360 Arabidopsis A plant genus of the family BRASSICACEAE that contains ARABIDOPSIS PROTEINS and MADS DOMAIN PROTEINS. The species A. thaliana is used for experiments in classical plant genetics as well as molecular genetic studies in plant physiology, biochemistry, and development. Arabidopsis thaliana,Cress, Mouse-ear,A. thaliana,A. thalianas,Arabidopses,Arabidopsis thalianas,Cress, Mouse ear,Cresses, Mouse-ear,Mouse-ear Cress,Mouse-ear Cresses,thaliana, A.,thaliana, Arabidopsis,thalianas, A.
D017931 DNA Primers Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques. DNA Primer,Oligodeoxyribonucleotide Primer,Oligodeoxyribonucleotide Primers,Oligonucleotide Primer,Oligonucleotide Primers,Primer, DNA,Primer, Oligodeoxyribonucleotide,Primer, Oligonucleotide,Primers, DNA,Primers, Oligodeoxyribonucleotide,Primers, Oligonucleotide
D018506 Gene Expression Regulation, Plant Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in plants. Plant Gene Expression Regulation,Regulation of Gene Expression, Plant,Regulation, Gene Expression, Plant
D019751 Intramolecular Transferases Enzymes of the isomerase class that catalyze the transfer of acyl-, phospho-, amino- or other groups from one position within a molecule to another. EC 5.4. Mutases,Transferases, Intramolecular
D020133 Reverse Transcriptase Polymerase Chain Reaction A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols. Polymerase Chain Reaction, Reverse Transcriptase,Reverse Transcriptase PCR,PCR, Reverse Transcriptase,Transcriptase PCR, Reverse

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