In recent years, researchers have adopted many new technologies to help und
erstand potyvirus pathogenesis. Their findings have illuminated key aspects
of the interactions between the host and the virus, and between the virus
and its aphid vector. This review focuses on advances in our understanding
of the molecular determinants of systemic infection, symptom expression, ap
hid and seed transmission, and natural and engineered resistance to potyvir
uses. Very recent developments in the area of post-transcriptional gene sil
encing indicate not only that the process is fundamental to engineered resi
stance, but may also underlie many aspects of the biology of plant viruses.