Citrus psorosis virus interferes with plant microRNA processing

REYES CA; OCOLOTOBICHE E; ROBLES LUNA G; BORNIEGO, MB; MARMISOLLÉ, FE; BAZZINI AA; ASURMENDI S; GARCIA ML

Washington

Simposio; Keystone Symposia on Molecular and Cellular Biology- RNA Silencing; 2014

Citrus psorosis virus (CPsV) is the type member of the genus Ophiovirus. Its genome consists of three ssRNAs of negative polarity that encodes four proteins: the RNA-dependent RNA polymerase of 280 kDa, the movement protein of 54 kDa (54K), the coat protein and a small protein of 24 kDa (24K). When sweet orange plants (Citrus sinensis (L.) Osbeck) are infected with CPsV a deregulation in conserved microRNA accumulation is observed. Levels of mature microRNA species were reduced with a concomitant up-regulation of their target genes. The processing intermediates of microRNA precursors were analyzed by Northern blot and an increased accumulation of pre-microRNAs was found in the infected samples comparing to the non infected ones. Particularly pre-miR156a (143 bp) is processed in two cuts in a loop to base fashion rendering two putative intermediates in the first cut (41 bp upper loop and two 51 bp comprising lower arms and mature). In infected samples accumulation of these processing intermediates were reduced in association to the increment of the non-processed precursor. These observations could be explained by interaction of a viral protein to precursors impeding the silencing machinery to access and process them. There are biochemical evidences of binding of 24K protein to long double strands RNAs in vitro. Besides, studies of subcellular localization have showed the 24K in discrete nuclear bodies, which could be coincident with the localization of DICER1 and HYL1 proteins involved in microRNA biogenesis.