Virus infection elevates transcriptional activity of miR164a promoter in plants

Abstract

BackgroundMicro 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.ResultsUsing 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.ConclusionThis 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.

ETHYLENE-INSENSITIVE3 Is a Senescence-Associated Gene That Accelerates Age-Dependent Leaf Senescence by Directly Repressing miR164 Transcription in Arabidopsis

“…To determine whether the EIN3-induced reduction of miR164 occurs by repressing miR164 transcription, we generated transgenic plants that harbor GUS driven by the miR164A promoter (pmiR164A:GUS) (Bazzini et al, 2009) in the Col-0, ein2-5, and ein3 eil1 backgrounds. We found that GUS activity significantly decreased in 5-d-old pmiR164A:GUS/Col-0 seedlings upon treatment with 100 mM ACC ( Figures 5G and 5I), indicating that ethylene negatively regulates miR164 transcription.…”

“…The pmiR164A:GUS construct, a 2522-bp fragment upstream of the foldback structure of miR164A, was provided by Sebastian Asurmendi (Bazzini et al, 2009). pmiR164A:GUS construct was introduced into Agrobacterium tumefaciens C58 and transformed into Col-0, ein3 eil1, or ein2-5 plants by floral dip (Clough and Bent, 1998).…”

“…To generate miR164A-LUC, the promoter was PCR amplified with primers as previously reported (Bazzini et al, 2009) and inserted into the cloning site of the pGreen0800-LUC vector. The miR164AP2D-LUC construct containing a deletion in the P2 sequence of the miR164A promoter was generated using overlap extension PCR and inserted into pGreen0800-LUC vector.…”

Small Non-Coding RNAs in Plant Immunity

“…For example miR1885 is induced in response to infection of Brassica rapa by Turnip mosaic virus and is known to target a TIR-NBS-LRR (TNL) disease-resistance gene [53]. miR164 is also induced upon viral infection and its induction is due to hormone-dependent specific transcriptional activation [54]. However, the effect of this differential regulation in the outcome of the interaction is not well established, as it may also result from the silencing suppression activity of the virus.…”

Isolation and characterization of the tissue and development-specific potato snakin-1 promoter inducible by temperature and wounding

“…For mechanical wounding treatments, leaves were gently pressed with a pair of sterilized serrated forceps as described Delessert et al (2005) and collected at 1, 2 or 3 hrs after wounding. Hormone treatments were performed according to Bazzini et al (2009). Briefly, plants subjected to hormone treatment were grown in 1.5 inches individual pots and sprayed with 50 ml of 100 μM ABA, 100 μM IAA, 50 μM GA3 or water (mock-treated) and incubated for 6 hrs under dim light.…”