Virus infection elevates transcriptional activity of miR164a promoter in plants.
BACKGROUND
Micro RNAs (miRs) constitute a large group of endogenous small RNAs that have crucial roles in many important plant functions. Virus infection and transgenic expression of viral proteins alter accumulation and activity of miRs and so far, most of the published evidence involves post-transcriptional regulations.


RESULTS
Using transgenic plants expressing a reporter gene under the promoter region of a characterized miR (P-miR164a), we monitored the reporter gene expression in different tissues and during Arabidopsis development. Strong expression was detected in both vascular tissues and hydathodes. P-miR164a activity was developmentally regulated in plants with a maximum expression at stages 1.12 to 5.1 (according to Boyes, 2001) along the transition from vegetative to reproductive growth. Upon quantification of P-miR164a-derived GUS activity after Tobacco mosaic virus Cg or Oilseed rape mosaic virus (ORMV) infection and after hormone treatments, we demonstrated that ORMV and gibberellic acid elevated P-miR164a activity. Accordingly, total mature miR164, precursor of miR164a and CUC1 mRNA (a miR164 target) levels increased after virus infection and interestingly the most severe virus (ORMV) produced the strongest promoter induction.


CONCLUSIONS
This work shows for the first time that the alteration of miR pathways produced by viral infections possesses a transcriptional component. In addition, the degree of miR alteration correlates with virus severity since a more severe virus produces a stronger P-miR164a induction.
Bazzini
Ariel A
AA
Instituto de Biotecnología, CICVyA, INTA Castelar, CP 1686 Hurlingham, Buenos Aires, Argentina. abazzini@cnia.inta.gov.ar
Almasia
Natalia I
NI
Manacorda
Carlos A
CA
Mongelli
Vanesa C
VC
Conti
Gabriela
G
Maroniche
Guillermo A
GA
Rodriguez
María C
MC
Distéfano
Ana J
AJ
Hopp
H Esteban
HE
del Vas
Mariana
M
Asurmendi
Sebastian
S
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000821:virology*; D003001:Cloning, Molecular; D019295:Computational Biology; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009029:Mosaic Viruses / Q000502:physiology*; D010935:Plant Diseases / Q000235:genetics / Q000821:virology; D010937:Plant Growth Regulators / Q000494:pharmacology; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000821:virology; D011401:Promoter Regions, Genetic; D018749:RNA, Plant / Q000235:genetics
C538852:MIRN164 microRNA, Arabidopsis; D035683:MicroRNAs; D010937:Plant Growth Regulators; D018749:RNA, Plant