Abstract
Grafting is an ancient technique used by farmers and gardeners to combine desired attributes of the rootstock with those of the donor plant shoot, or scion. Grafting essentially saved European wine making: when the insect Dactylosphera vitifoliae devastated European grapewine varieties over the course of the late 1800s and early 1900s, the varieties were saved by grafting them onto resistant rootstocks from the New World. Since then, these rootstocks have been used to maintain the susceptible Old World cultivars. But grafting is also an excellent tool for scientists studying systemic signals traveling between the rootstock and distal parts of the plants, and vice versa. For example, two important studies (Palauqui et al. 1997; Voinnet et al. 1998) used grafting to demonstrate the spreading of RNA silencing in plants. However, it was a subsequent paper (Crete et al. 2001) that followed up on certain inconsistencies in the grafting results that pointed to subtleties important for both experimental design and understanding systemic signaling in plants.
Highlights
RNA silencing (termed posttranscriptional gene silencing in plants, quelling in fungi, and RNA interference in animals) refers to the phenomenon whereby specific gene transcript levels are reduced in the presence of a related RNA
RNA silencing refers to the phenomenon whereby specific gene transcript levels are reduced in the presence of a related RNA
Posttranscriptional gene silencing spreads systemically throughout the individual plants in a very characteristic manner reminiscent of viral spread. This has led to the hypothesis of a systemic silencing signal that is produced in the tissues where silencing is initiated and is transmitted to the distant parts of the plant where it can initiate silencing in a sequence-specific manner
Summary
RNA silencing (termed posttranscriptional gene silencing in plants, quelling in fungi, and RNA interference in animals) refers to the phenomenon whereby specific gene transcript levels are reduced in the presence of a related RNA. This has led to the hypothesis of a systemic silencing signal that is produced in the tissues where silencing is initiated and is transmitted to the distant parts of the plant where it can initiate silencing in a sequence-specific manner. They used as a stock a transgenic tobacco carrying an additional copy of the endogenous nitrate reductase gene, Nia. Some of the transgenic lines generated always showed higher levels of Nia transcripts than the wild type—as expected from the presence of an additional gene—and were termed class I lines.
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