Citrus psorosis virus interferes with plant microRNA processing

CARINA ANDREA REYES; ELIANA EVELINA OCOLOTOBICHE; GABRIEL ROBLES LUNA ; BELÉN BORNIEGO; FACUNDO MARMISOLLE; ARIEL BAZZINI; SEBASTIAN AZURMENDI; MARÍA LAURA GARCÍA

Simposio; RNA silencing; 2014

Citrus psorosis virus 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, the coat protein and a small protein of 24K KDa. When sweet orange plants (Citrus sinensis (L.) Osbeck) are infected with CPsV a deregulation in conserved microRNA accumulation is observed with a tendency to a reduction in the levels of the mature microRNAs. Targets genes of the down regulated microRNAs were concomitantly up-regulated. The processing intermediates of microRNA precursors were analyzed by Northern blot and a higher accumulation of non processed pre-microRNAs was found in the infected samples comparing to the non infected ones. Particularly pre-miR156 (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; two 51 bp comprising lower arms and mature). In infected samples accumulation of those intermediates were reduced in association to the increment of the non-processed precursor. This could be explained by interaction of the viral protein 24K to precursors impeding the silencing machinery to access and process them. There are biochemical evidences of binding of this protein to long double strands RNAs in vitro. Besides, the subcellular localization of 24K in discrete nuclear bodies coincides with the localization of DICER1 and HYL1 proteins involved in microRNA biogenesis.