Structural and functional exploration of p7 protein from HPWMoV

High Plains Wheat Mosaic virus (HPWMoV) is a newly discovered Emaravirus, transmitted by the wheat curl mite (Aceria tosichella Keifer), and it is the causative agent of the High Plains disease in wheat, maize and other cereal grains. HPWMoV, harbors an octa-partite ssRNA(-) genome, segment RNA S1 – through S8.

In plants, RNA silencing is an important strategy for fighting viral infections through transcriptional and post-transcriptional gene silencing. Throughout evolution, viruses developed countermeasures to evade RNA silencing using viral RNA silencing suppressors (RSSs). Recently it was shown that segments S7 and- S8 encodes to two RSS proteins, termed P7 and P8, that likely to have different RNA silencing suppression mechanisms. Little is known about these proteins and how they function, their structure, and biochemical properties.

Our main focus is to determine the structure and RSS mechanism of P7 from HPWMoV we expressed, and biochemically determined the boundaries of the main domain in P7. We are using X-Ray crystallography, biochemistry and biophysics approach to unravel the underlay the RSS activity of this protein. An AlphaFold prediction of P7’s structure rationalized a design of a new construct for bacteria expression.

Our preliminary results show the purification, hydrodynamic properties and domain boundary determination using limited proteolysis. Crystal structure of P7 will be the basis for exploring its functional landscape using structure-based mutagenesis which reveal the biochemical activity of this protein.

Structural investigation of RSS proteins from HPWMoV will allow developing new strategies to fight these important agricultural threats.