The impact of phytohormones on virus infection and disease

• Viruses target phytohormone signaling to disarm defenses and promote infection.
• Virus disruption of phytohormone pathways can result in disease symptoms.
• Cross-talk between phytohormone pathways contributes to virus defense.
• Studies on mechanisms viruses use to modulate phytohormone pathways are needed.

Phytohormones play a critical role in nearly every aspect of plant biology, including development and pathogen defense. During virus infection disruption of the plant's normal developmental physiology has often been associated with alterations in phytohormone accumulation and signaling. Only recently has evidence emerged describing mechanistically how viruses modulate phytohormone levels and the impact these modulations have on plant physiology and virus biology. From these studies there is an emerging theme of virus directed manipulation of plant hormone responses to disarm defense responses and reprogram the cellular environment to enhance replication and spread. In this review we examine the impact viruses have on plant hormone systems and the effects of this phytohormone manipulation on virus biology.