Minor component of the viral capsid involved in aphid transmission and virus accumulation in the host (Probable). Required for the virus to move through the aphid (By similarity). The RTD domain of the protein is exposed on the surface of the particle and determines the vector specificity and intestinal tropism in the aphid (By similarity). This domain might also determine the limitation of the virus to the host phloem (PubMed:19297484). Participates, together with the proteins P0 and P1, in the inhibition of the induction of aphid-induced host phytohormones (PubMed:31758809). This could play a role in the attraction to the infected plants by aphids (PubMed:31758809). P7 is the translated product of subgenomic RNA sgRNA3. The N-terminus is highly basic like those of many plant virus capsid proteins. It has been suggested that these regions may be involved in protein-RNA interaction (Probable). The RTD N-terminus is responsible for aphid transmission and aphid endosymbiont interaction (By similarity). The readthrough domain is required for transport of virus through membranes of the aphid salivary glands (By similarity). In virus particles, more than 200 amino acids are proteolytically cleaved releasing the C-terminus part of the RTD domain (PubMed:7513925, PubMed:2230732). The cleaved product remains attached to the virus particle (PubMed:7513925). This protein is translated as a fusion protein by episodic readthrough of the major coat protein termination codon. It is composed of the major capsid protein fused to a long C-terminal extension called the readthrough domain (RTD). Readthrough of the terminator codon TAG occurs between the codons for 208-Lys and 210-Val. Belongs to the luteoviruses readthrough protein family.