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Spontaneous short‐range silencing of a GFP transgene in Nicotiana benthamiana is possibly mediated by small quantities of siRNA that do not trigger systemic silencing
Author(s) -
Kalantidis Kriton,
Tsagris Mina,
Tabler Martin
Publication year - 2006
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2006.02664.x
Subject(s) - nicotiana benthamiana , transgene , gene silencing , green fluorescent protein , biology , small interfering rna , cauliflower mosaic virus , agrobacterium , rna silencing , nicotiana , microbiology and biotechnology , potato virus x , rna interference , virus , rna , genetically modified crops , virology , genetics , plant virus , gene , solanaceae
Summary A green fluorescent protein (GFP) transgene under the control of the 35S cauliflower mosaic virus (CaMV) promoter was introduced by Agrobacterium ‐mediated transformation into Nicotiana benthamiana to generate fourteen transgenic lines. Homozygous lines that contained one or two copies of the transgene showed great variation of GFP expression under ultraviolet (UV) light, which allowed classification into three types of transgenic plants. Plants from more than half of the transgenic lines underwent systemic RNA silencing and produced short interfering RNA (siRNA) as young seedlings, while plants of the remaining lines developed, in a spontaneous manner, defined GFP‐silenced zones on their leaves, mostly in the form of circular spots that expanded to about 4–7 mm in size. In some of the latter lines, the GFP‐silenced spots remained stable, but no systemic silencing occurred. Here we characterize this phenomenon, which we term spontaneous short‐range silencing (SSRS). Biochemical analysis of silenced spot tissue did not reveal detectable levels of siRNA. However, agro‐infiltration with the suppressor proteins P19 of cymbidium ring spot virus (CymRSV), HC‐Pro of tobacco etch virus (TEV), and crosses to a P19 transgenic line, nevertheless suggests that low concentrations of siRNA may have a functional role in the locally silenced zone. We propose that small alterations in the steady‐state concentration of siRNAs and their cognate mRNA are decisive with regard to whether silencing remains local or spreads in a systemic manner.