Tobamovirus infections alter miRNA abundance and activity in two phases, one early and systemic and a second one late and dependent of virus accumulation

BAZZINI, AA; MANACORDA, CA; CONTI, G; ASURMENDI, S

Keystone - Colorado – USA

Simposio; Keystone Symposia on Molecular and Cellular Biology; 2010

MicroRNAs (miRs) are involved in many different cell processes, including development and response to biotic and abiotic stresses. We describe a positive correlation between severity of disease symptoms and alteration of miRs and miR-targets accumulation in Nicotiana tabacum after infection with six tobamoviruses differing on their severity. More interestingly we identified a previously unnoticed temporal miR alteration phase at early stages of infection. While virus was still undetectable in the sampled systemic leaf, the level of miRs measured by qRT-PCR decreased and consequently produced the expected rise of miR-target levels. This data suggested the action of a systemic signal that might alter the miR pathway at early times of infection. A second miR interference phase was detected at later stages of infection, depending on virus accumulation. On the latter case, both miRs and miR-targets were increased, most probably as a consequence of viral post-transcriptional gene silencing suppressors activity, in agreement with previous reports. These two phases were also clearly evidenced by data of a microarray analysis of miRs produced using RNA of TMV-infected tobacco systemic leaves at different time points along the infection. Fifteen out of twenty miRs altered by the infection were down-regulated at the early stage and up-regulated at the late stages of infection, correlating with the level of virus accumulation in the sampled leaf. These results introduce a new stance in the host-pathogen interaction, highlighting the early stage of the infection and the relevance of the role of miRs in the production of symptoms. This research was supported by PICT 2005 Nº 32598 from ANPCyT and by AEBIO3454 from INTA.