Aphids feed from the plant phloem sap and are responsible for large damage on crops by either weakening the plant or transmitting plant viruses that circulate in the sap.
Can we use transgenic plants to limit aphid negative impact on plants? And if yes, which efficient technical means can we develop?
Guo et al in the lab of Rongxiang Fang in Beijing, propose to generate in planta, small interfering RNAs targeting key physiological functions of aphids: the hypothesis is that during feeding, uptake by aphids of these small interfering RNAs produced in the sap might affect aphid fitness and protect the plant.
Choosing the insect target genes and transgenic plants
The authors selected 9 aphid genes involved in general physiological functions and that could be essential for insect fitness. These genes are an ATPase subunit, a cuticule protein, ribosomal proteins (2 different), a chromatin regulator, a tubulin, a coatomer, and an acetylcholinesterase and two microRNAs targeting this acetylcholinesterase. Transgenic tobacco plants containing hairpin RNAs of these targets have been produced, as well of transgenes expressing the two microRNA, using the backbone of a plant pre-microRNA gene. The plant promoters used for the in planta expression of these transgenes is the 35S of CaMV, known to be ubiquitously expressed at high level, also in phloem companion cells.
Phenotype of the transgenic plants
Several green peach aphid (Myzus persicae) individuals were fed on wild-type or transgenic plants, and the number of progeny produced by these aphids was recorded, as a measure of the fitness of aphids on the different plants, in comparison to the wild-type and a control made of transgenic plants transformed with an empty vector.
An average reduction of 25% in the number of produced progeny can be observed in most of the transgenic plants. The in planta expression of microRNAs targeting the acetylcholinesterase mRNAs had a slightly higher effect than the expression of the hairpin RNA of acetylcholinesterase. Whether or not this might be sufficient to alleviate plants against aphid attacks remains to be proved and the technique still needs improvement.
These experiments showed that most of these transgenic plants can be used for modifying aphid fitness when feeding.
This paper confirms that plants can be used as “vectors” for modifying aphid gene expression; an important breakthrough, for species such as aphids for which transgenics are still not available.
Plant-Generated Artificial Small RNAs Mediated Aphid Resistance 2014, Guo H, Song X, Wang G, Yang K, Wang Y, Niu, Chen X and Fang R, PLOS ONE vol 9 (5) e97410