TYLCV-Is movement in planta does not require V2 protein.

Area of Science:

• Plant virology
• Molecular biology
• Agricultural science

Background:

• Tomato yellow leaf curl virus (TYLCV) is a significant pathogen causing substantial tomato crop losses.
• The V2 protein of TYLCV was previously hypothesized to function as a movement protein, based on observations of attenuated viral DNA levels in infected plants.

Purpose of the Study:

• To investigate the precise role of the V2 protein in TYLCV infection, specifically its involvement in viral movement and proliferation.
• To differentiate between the functions of V2 in viral movement versus its role as a viral silencing suppressor.

Main Methods:

• Generation and analysis of two TYLCV V2 mutants: one with impaired silencing-suppression activity and another with a non-translatable V2.
• Monitoring the spread of mutant viruses to newly emerged leaves in infected plants.
• Quantification of viral DNA accumulation levels in plants infected with wild-type and mutant viruses.

Main Results:

• Both V2 mutant viruses exhibited similar rates of spread to new leaves as the wild-type TYLCV.
• However, the DNA accumulation levels of the mutant viruses were tenfold lower compared to the wild-type virus.
• The V2 protein's silencing-suppression activity, not its movement function, was found to be critical for efficient viral proliferation.

Conclusions:

• The reduced proliferation observed in V2 mutants is primarily attributed to the loss of V2's silencing-suppression activity, rather than a defect in viral movement.
• This study re-evaluates the function of the V2 protein, highlighting its crucial role in overcoming plant antiviral defense mechanisms for successful viral replication.