standard Extreme Transgenerational Gene Silencing

Sitobion

Sitobion avenae.
Image Credit: David Cappaert, Michigan State University, Bugwood.org, on invasive.org

RNAiAbdellatef et al. (2015) recently published the results of their efforts to silence the salivary sheath protein gene in the aphid Sitobion avenae in the Plant Biotechnology Journal and observed what might be called extreme transgenerational gene silencing.

Plant-expressed dsRNA targeting insect genes has been shown to be a viable option for deterring feeding by some herbivors.  The efficacy of this method is determined in part by the choice of target genes and the sensitivity of the target insect to gene silencing following ingestion of dsRNA.

Abdellatef et al (2015) were testing the structural sheath protein (SHP) as a target of gene silencing in aphids – specifically Sitobion avenae.  SHP is a component of aphid saliva that surrounds the stylet and is thought to play a variety of roles.

https://upload.wikimedia.org/wikipedia/commons/2/20/Barley_%28Hordeum_vulgare%29_-_United_States_National_Arboretum_-_24_May_2009.jpg

Hordeum vulgare, Barley Image Credit

The authors created transgenic barley plants simultaneously and ubiquitously expressing sense and antisense copies of a 500 bp fragment of shp.

The authors report that aphids feeding on these plants had effective silencing of shp compared to aphids feeding on wild-type plants or those with the transgene vector but without the effector transgenes, and this silencing showed a high degree of perdurance.  After removing aphids from ‘silencing’ plants and putting them on wild-type plants shp expression remained low for weeks.

Interestingly, shp expression was almost equally low in the second generation of aphids feeding on wild-type plants.

Stylet

Aphid stylet in relation to plant cells.

More interestingly and unexpectedly shp expression was significantly lower in 4th-, 5th- and 6th-generation aphids.  Levels of shp expression increased steadily beginning in the first generation but was significantly lower than wild-type levels through the 6th generation.

So, Abdellatef et al (2015) report what appears to be an extreme example of transgenerational gene silencing.  Of course, the telescoping generations seen in aphids make some level of transgenerational gene silencing in aphids somewhat expected but seeing effects through the 6th generation is interesting and intriguing.

The authors discuss possible mechanism and it is worth taking a look at the paper to get all of the details.

Adellatef, E., Will, T., Koch, A., Imani, J., Vilcinskas, A. and Kogel, K-H. (2015) Silencing the expression of the salivary sheath protein causes transgenerational feeding suppression in the aphid Sitobion avenae. Plant Biotechnology Journal 13:849-857, doi: 10.1111/pbi.12322

 

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