Intriguingly, coinfection of ST9 with the polerovirus beet western yellows virus (BWYV) has been shown to produce more severe symptoms and lead to higher accumulation of BWYV RNA than in single infections (11).While the molecular mechanisms underlying the increased symptom severity observed in coinfections of BWYV and tlaRNA ST9 have yet to be elucidated (Falk and Duffus, 1984), it is worth noting the stalling of XRN1 by ST9 RNAs could play a role. Here, XRN1 is linked to infection.