SnRK1: a versatile plant protein kinase that limits geminivirus infection.

Geminiviruses are a family of single-stranded DNA viruses that infect many plant species and cause serious diseases in important crops. The plant protein kinase, SnRK1, has been implicated in host defenses against geminiviruses. Overexpression of SnRK1 makes plants more resistant to geminivirus infection, and knock-down of SnRK1 increases susceptibility to geminivirus infection. GRIK, the SnRK1 activating kinase, is upregulated by geminivirus infection, while the viral C2 protein inhibits the SnRK1 activity. SnRK1 also directly phosphorylates geminivirus proteins to reduce infection. These data suggest that SnRK1 is involved in the co-evolution of plant hosts and geminiviruses.