Plant biology

siRNA Movement in Plant Tissues

Science Signaling  18 May 2010:
Vol. 3, Issue 122, pp. ec151
DOI: 10.1126/scisignal.3122ec151

Long-distance movement of RNA interference (RNAi)–derived signals in plants plays an important role in development and in defense against viral attack. The nature of the signals that spread from cell to cell is not known, although evidence suggests that they are nucleic acids of some sort (see the Perspective by Martienssen). Molnar et al. and Dunoyer et al. now show that in Arabidopsis, both exogenous and endogenous small interfering RNAs (siRNAs), rather than their long double-stranded precursor RNAs, are the molecules that transfer information between plant cells. A viral protein that counters RNAi though sequestering siRNAs blocked spreading of a transgene RNAi silencing signal. Furthermore, siRNA-processing enzymes were required in the source, and not the recipient, cells for spreading, and bombardment of plants with double-stranded siRNAs directly showed siRNA spread between cells. Endogenous siRNAs also spread between tissues and were capable of directing DNA methylation of target sequences in distant tissues.

A. Molnar, C. W. Melnyk, A. Bassett, T. J. Hardcastle, R. Dunn, D. C. Baulcombe, Small silencing RNAs in plants are mobile and direct epigenetic modification in recipient cells. Science 328, 872–875 (2010). [Abstract] [Full Text]

P. Dunoyer, G. Schott, C. Himber, D. Meyer, A. Takeda, J. C. Carrington, O. Voinnet, Small RNA duplexes function as mobile silencing signals between plant cells. Science 328, 912–916 (2010). [Abstract] [Full Text]

R. Martienssen, Small RNA makes its move. Science 328, 834–835 (2010). [Summary] [Full Text]