Javier F Palatnik

Publications (34) View all

• Article: MicroRNA miR396 and RDR6 synergistically regulate leaf development.

  Martin A Mecchia, Juan M Debernardi, Ramiro E Rodriguez, Carla Schommer, Javier F Palatnik
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  ABSTRACT: The microRNA (miRNA) miR396 regulates GROWTH-REGULATING FACTORs (GRFs), a plant specific family of transcription factors. Overexpression of miR396 causes a decrease in the GRFs that has been shown to affect cell proliferation in the meristem and developing leaves. To bring further insights into the function of the miR396 regulatory network we performed a mutant enhancer screen of a stable Arabidopsis transgenic line expressing 35S:miR396b, which has a reduction in leaf size. From this screen we recovered several mutants enhancing this phenotype and displaying organs with lotus- or needle-like shape. Analysis of these plants revealed mutations in as2 and rdr6. While 35S:miR396b in an as2 context generated organs with lotus-like shape, the overexpression of the miRNA in an rdr6 mutant background caused more important developmental defects, including pin-like organs and lobed leaves. Combination of miR396 overexpressors, and rdr6 and as2 mutants show additional organ defects, suggesting that the three pathways act in concert. Genetic interactions during leaf development were observed in a similar way between miR396 overexpression and mutants in RDR6, SGS3 or AGO7, which are known to participate in trans-acting siRNA (ta-siRNA) biogenesis. Furthermore, we found that miR396 can cause lotus- and pin-like organs per se, once a certain expression threshold is overcome. In good agreement, mutants accumulating high levels of TCP4, which induces miR396, interacted with the AS1/AS2 pathway to generate lotus-like organs. The results indicate that the miR396 regulatory network and the ta-siRNA biogenesis pathway synergistically interact during leaf development and morphogenesis.
  Mechanisms of development 08/2012; · 2.83 Impact Factor
• Article: Identification of new microRNA-regulated genes by conserved targeting in plant species.

  Uciel Chorostecki, Valeria A Crosa, Anabella F Lodeyro, Nicolás G Bologna, Ana P Martin, Néstor Carrillo, Carla Schommer, Javier F Palatnik
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  ABSTRACT: MicroRNAs (miRNAs) are major regulators of gene expression in multicellular organisms. They recognize their targets by sequence complementarity and guide them to cleavage or translational arrest. It is generally accepted that plant miRNAs have extensive complementarity to their targets and their prediction usually relies on the use of empirical parameters deduced from known miRNA-target interactions. Here, we developed a strategy to identify miRNA targets which is mainly based on the conservation of the potential regulation in different species. We applied the approach to expressed sequence tags datasets from angiosperms. Using this strategy, we predicted many new interactions and experimentally validated previously unknown miRNA targets in Arabidopsis thaliana. Newly identified targets that are broadly conserved include auxin regulators, transcription factors and transporters. Some of them might participate in the same pathways as the targets known before, suggesting that some miRNAs might control different aspects of a biological process. Furthermore, this approach can be used to identify targets present in a specific group of species, and, as a proof of principle, we analyzed Solanaceae-specific targets. The presented strategy can be used alone or in combination with other approaches to find miRNA targets in plants.
  Nucleic Acids Research 07/2012; 40(18):8893-904. · 8.03 Impact Factor
• Article: A loop-to-base processing mechanism underlies the biogenesis of plant microRNAs miR319 and miR159.

  Nicolás G Bologna, Julieta L Mateos, Edgardo G Bresso, Javier F Palatnik
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  ABSTRACT: The first step in microRNA (miRNA) biogenesis usually involves cleavage at the base of its fold-back precursor. Here, we describe a non-canonical processing mechanism for miRNAs miR319 and miR159 in Arabidopsis thaliana. We found that their biogenesis begins with the cleavage of the loop, instead of the usual cut at the base of the stem-loop structure. DICER-LIKE 1 (DCL1) proceeds then with three additional cuts until the mature miRNA is released. We further show that the conserved upper stem of the miR319 precursor is essential to organize its biogenesis, whereas sequences below the miRNA/miRNA(*) region are dispensable. In addition, the bulges present in the fold-back structure reduce the accumulation of small RNAs other than the miRNA. The biogenesis of miR319 is conserved in the moss Physcomitrella patens, showing that this processing mechanism is ancient. These results provide new insights into the plasticity of small-RNA pathways.
  The EMBO Journal 10/2009; 28(23):3646-56. · 9.20 Impact Factor
• Article: Parallel screening and optimization of protein constructs for structural studies.

  Rodolfo M Rasia, Marjolaine Noirclerc-Savoye, Nicolás G Bologna, Benoit Gallet, Michael J Plevin, Laurence Blanchard, Javier F Palatnik, Bernhard Brutscher, Thierry Vernet, Jérôme Boisbouvier
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  ABSTRACT: A major challenge in structural biology remains the identification of protein constructs amenable to structural characterization. Here, we present a simple method for parallel expression, labeling, and purification of protein constructs (up to 80 kDa) combined with rapid evaluation by NMR spectroscopy. Our approach, which is equally applicable for manual or automated implementation, offers an efficient way to identify and optimize protein constructs for NMR or X-ray crystallographic investigations.
  Protein Science 01/2009; 18(2):434-9. · 2.80 Impact Factor
• Source

  Available from: Alberto Acevedo

  Article: Status of antioxidant metabolites and enzymes in a catalase-deficient mutant of barley (Hordeum vulgare L.)

  Javier F Palatnik, Estela M Valle, María L Federico, Leonardo D Gó Mez, Mariana N Melchiorre, Antonio Díaz Paleo, Néstor Carrillo, Alberto Acevedo
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  ABSTRACT: We have investigated the antioxidant status in RPr79/4, a CAT-deficient mutant of barley, and in its motherline, cv. Maris Mink. Seedlings of the CAT-deficient mutant that were grown in a growth chamber under a 14-h photoperiod (200 mmol quanta m − 2 s − 1), exhibited higher concentrations of glutathione and ascorbate peroxidase as compared to wild-type plants. An additional mitochondrial MnSOD isoenzyme, was also detected in RPr79/4. When seedlings of the CAT-deficient mutant were grown at higher light intensities (370 mmol quanta m − 2 s − 1), a Cu/ZnSOD isoform and the cytosolic glutamine synthetase isoenzyme were concomitantly induced. Taken together, these results suggest that several defense mechanisms operating in different subcellular compartments respond in concert to compensate for CAT deficiency in barley seedlings exposed to oxidative stress.
  Plant Science. 01/2002; 162:363-371.