P-230 - AGO5 restricts virus vertical transmission in plant gametes

Virus vertical transmission—the passage of viral infection from parent to progeny—is a key mechanism for virus persistence across generations and geographical regions. It is especially significant in plants, where viruses spread both locally and globally via pollen and seeds, but it is often inefficient or entirely absent, suggesting the existence of very effective yet unknown transgenerational antiviral barriers. Here, we demonstrate that AGO5, an RNA interference factor specifically expressed in meristematic stem cells and gametes, plays a crucial role in restricting vertical transmission of Turnip yellow mosaic virus in A. thaliana. Using reciprocal crosses we show that AGO5 suppresses viral transmission through both male and female parents. Analysis of heterozygous ago5 knock-out mutants revealed that AGO5 restricts vertical transmission post-meiosis and pre-fertilization during host reproduction, emphasizing its gametophyte- and gamete-specific antiviral activity while excluding involvement in the zygote or embryo. Production of virus-specific small RNAs in sperm cells significantly reduced pollen-mediated virus transmission, as did sperm cell-specific expression of AGO5 in ago5 mutants, further validating the gamete-specific function of AGO5. Collectively, we unveil the first known antiviral mechanism restricting RNA virus transmission from parent to progeny in gametes, a significant advance that will increase our toolkit in the management of viral diseases.