In VIGS we silence genes but i wish to know if the silencing signal spreads in root or not. Putting it in other way, are silencing signals by VIGS or dS RNA degradation spreads equally from top (shoot/leaf) to bottom (roots) and bottom to roots (consider a RNAi construct in hairy root or VIGS) in plant systems.
HI Kama,
I am not sure whether the silencing sginal will spread equally in root and shoots (or other tissues) or not. But there are several reports showing that small RNAs do spread form shoots to roots to silence genes there...
The use of VIGS is an efficient, fast, and reproducible way to induce gene silencing in plants, however the equally spreading of its effect is not guaranteed, to achieve a uniform effect you should carry out several replicates (9 instead of 3) to ensure that the silencing effect is consistent.
The only way to ensure a most regular spreading for your silencing in a plant system is to generate transgenic plants with the careful to choose the correct promoter (CaMV35S could work well since is not tissue specific, or a promoter such as CAB [chlorophyll AB binding protein] specific for leaf tissue).
Regards
1. Please refer to the attached paper (EMBO, 2011). It is a nice review about the movement of the mRNA silencing signal. It entitled "Intercellular and systemic movement of RNA silencing signals".
2. In the article, it notes that there is evidence of transgenes that escape silencing in meristems or that are only weakly silent in dividing cells (see the paragraph of Meristems)
An RNAi construct with a universal promoter such as Ubiquitin might help even suppression in whole plant.
Friends thanks. I am still not clear whether the VIGS signal will reach roots/root hairs or the hairy root silencing signals will reach the leaves.
Dear Kumar,
There is some evidence that the rootstock can silence virus expression in a scion when grafted with a resistante rootstock, and the symptoms disappear in the scion. However, the exact mechanism is not clear understood, but it is through the action of microRNAs are believed to be induced by the rootstock, silencing or inhibiting virus replication. Therefore, the effect may be specific to some characters but has yet to be proven.
Nature Communications Vol 9, Article Number: 3107 (2018) entitled "
Gating of miRNA movement at defined cell-cell interfaces governs their impact as positional signals" explains a lot of this question.
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