Induction, suppression and requirement of RNA silencing pathways in virulent Agrobacterium tumefaciens infections.
Regulation of gene expression through microRNAs (miRNAs) and antiviral defense through small interfering RNAs (siRNAs) are aspects of RNA silencing, a process originally discovered as an unintended consequence of plant transformation by disarmed Agrobacterium tumefaciens strains. Although RNA silencing protects cells against foreign genetic elements, its defensive role against virulent, tumor-inducing bacteria has remained unexplored. Here, we show that siRNAs corresponding to transferred-DNA oncogenes initially accumulate in virulent A. tumefaciens-infected tissues and that RNA interference-deficient plants are hypersusceptible to the pathogen. Successful infection relies on a potent antisilencing state established in tumors whereby siRNA synthesis is specifically inhibited. This inhibition has only modest side effects on the miRNA pathway, shown here to be essential for disease development. The similarities and specificities of the A. tumefaciens RNA silencing interaction are discussed and contrasted with the situation encountered with plant viruses.
Dunoyer
Patrice
P
CNRS UPR2357, IBMP, Strasbourg, France.
Himber
Christophe
C
Voinnet
Olivier
O
D016960:Agrobacterium tumefaciens / Q000235:genetics* / Q000472:pathogenicity*; D017360:Arabidopsis / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D007438:Introns / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics; D009154:Mutation / Q000235:genetics; D018515:Plant Leaves / Q000033:anatomy & histology / Q000382:microbiology; D018517:Plant Roots / Q000033:anatomy & histology / Q000382:microbiology; D018547:Plant Stems / Q000033:anatomy & histology / Q000382:microbiology; D010941:Plant Tumors / Q000235:genetics / Q000382:microbiology*; D030821:Plants, Genetically Modified; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D014026:Nicotiana / Q000382:microbiology; D014774:Virulence / Q000235:genetics
D035683:MicroRNAs; D012333:RNA, Messenger; D034741:RNA, Small Interfering