Biological role of miR398 in tobacco

ANABELLA F. LODEYRO; ANA P. MARTIN; HUGO O. POLI; NÉSTOR CARRILLO; JAVIER PALATNIK

San Miguel de Tucumán

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

MicroRNAs (miRNAs) are a class of non-coding small RNAs of roughly 21nucleotides. They negatively regulate gene expression at the posttranscriptionallevel by perfect or nearly-perfect base pairing to complementarytarget mRNAs. Plant miRNAs were initially reported to be involved in growthand development patterning. Recently, miRNAs have also emerged as a classof gene expression regulators involved in different abiotic stresses. InArabidopsis, the down-regulation of miR398 expression is important for theinduction of the mRNA levels of two Cu/Zn superoxide dismutases (SODs)under high copper levels. SODs form the first line of defense against superoxideradicals. Surprisingly, results obtained in Arabidopsis thaliana indicate that themiR398 system is mainly implicated in copper homeostasis and has a minorrole in the response against oxidative stress. In order to investigate thebiological role of miR398 in plants from a broader perspective, we preparedtransgenic tobacco plants with high levels of the miRNA. Nicotiana tabacum, cvPetit Havana expressing Arabidopsis MIR398a and MIR398b precursors fromthe 35S viral promoter were prepared. Overexpression of miR398 resulted inthe nearly complete inactivation of the Cu/Zn SODs in tobacco, as judge byactivity gels. The biological role of the miR398 system in tobacco plants will bediscussed.