24K Citrus psorosis virus protein interferes with plant miRNA biogenesis and function

MARMISOLLÉ, FE; ASURMENDI S; OCOLOTOBICHE E; BAZZINI AA; REYES CA; BAEZA, C; GARCIA ML

Keystone, Colorado

Simposio; Keystone Symposia on Molecular and Cellular Biology- Small RNA Silencing: Little Guides, Big Biology; 2016

Sweet orange (Citrus sinensis) is one of the most important fruit crops worldwide. Disease symptoms caused by virus infections can interfere with cellular processes causing dramatic economic losses. Citrus psorosis virus (CPsV) genome consists of three single-stranded RNAs of negative polarity encoding four proteins: the RNA-dependent RNA polymerase, the movement protein (54K), the coat protein and a small protein of 24 kDa (24K). Here we demonstrate that infection of sweet orange plants with CPsV alters processing of a group of conserved pre-miRNAs leading to a reduction in mature miRNA species. miR156, miR167 and miR171 were the strongest down-regulated in infected samples with a concomitant up-regulation of some of its targets. Co-immunoprecipitation of viral proteins and pre-miR156a or pre-miR171a were performed and an association between the viral 24K protein and the assayed precursors was evidenced, suggesting that processing alteration might be due to direct or indirect interaction of miRNA precursors with 24K in the nucleus. On the other hand, transient expression assays of a reporter construct consisting in a miRNA target sequence fused to GFP together with 24K, also shows an inhibitory effect of this viral protein over the effector function of RISC complex. The co-expression of 54K with 24K reinforce the mentioned inhibitory effect. This work contributes to the understanding of how virus can alter host regulatory mechanisms at different levels, particularly miRNAs biogenesis in the nucleus and their function in the cytoplasm.