Temporal profile of juvenility-associated microRNAs during tissue culture of avocado

MicroRNAs are a group of non-coding small RNAs of 21-22 nucleotides found in many multicellular organisms including both animals and plants. They are highly conserved across many plant species and play a key role in regulating plant development by either directing cleavage of complimentary mRNAs or by translational inhibition. Avocado (Persea americana Mill.) is a high value tropical fruit crop which could be benefited through tissue culture to improve propagation of elite lines. Many morphological, physiological, biochemical and molecular changes occur during the in vitro tissue culture process. It has been hypothesised that the tissue culture process restores juvenile characteristics to explants obtained from physiologically mature mother plants. This hypothesis was examined in the current study by profiling expression levels of two highly conserved microRNAs (miR156 and miR172) involved in juvenile-to-adult phase change. The preliminary results reveal that miR172, a marker for plant maturity, is significantly reduced during the in vitro culture process. This is the first molecular indication of physiologically mature avocado material regaining juvenility characteristics as a result of the tissue culture process.