A surveillance system regulates selective entry of RNA into the shoot apex.
Phloem-mobile endogenous RNA is trafficked selectively into the shoot apex. In contrast, most viruses and long-distance post-transcriptional gene silencing (PTGS) signals are excluded from the shoot apex. These observations suggest the operation of an underlying regulatory mechanism. To examine this possibility, a potexvirus movement protein, known to modify cell-to-cell trafficking and PTGS, was expressed ectopically in transgenic plants. These plants were found to be compromised in their capacity to exclude both viral RNA and silencing signals from the shoot apex. The transgenic plants also displayed various degrees of abnormal leaf polarity depending on transgene expression level. Normal patterns of organ development were restored by either virus- or Agrobacterium tumefaciens-mediated induction of PTGS. This revealed the presence of an RNA signal surveillance system that acts to allow the selective entry of RNA into the shoot apex. We propose that this surveillance system regulates signaling and protects the shoot apex, in particular the cells that give rise to reproductive structures, from viral invasion.
Horticulture and Food Research Institute of New Zealand, Tennent Drive, Private Bag 11030, Palmerston North, New Zealand.
Toshi M
TM
Foster
Tony J
TJ
Lough
Sarah J
SJ
Emerson
Robyn H
RH
Lee
John L
JL
Bowman
Richard L S
RL
Forster
William J
WJ
Lucas
D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D015967:Gene Expression Regulation, Viral; D020868:Gene Silencing / Q000502:physiology; D017403:In Situ Hybridization; D010641:Phenotype; D018515:Plant Leaves / Q000254:growth & development; D018520:Plant Shoots / Q000235:genetics* / Q000821:virology; D030821:Plants, Genetically Modified; D017863:Potexvirus / Q000235:genetics / Q000502:physiology; D018749:RNA, Plant / Q000235:genetics* / Q000378:metabolism; D012261:Ribonucleoproteins / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics; D014026:Nicotiana / Q000235:genetics* / Q000821:virology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D018749:RNA, Plant; D012261:Ribonucleoproteins; D014764:Viral Proteins; C436445:triple gene block protein, White clover mosaic virus