Temporal profile of juvenility-associated microRNAs during tissue culture of avocado (Jayeni Chathurika Amarathunga Hiti Bandaralage)
Morphological, physiological, biochemical and molecular changes occur during the in vitro tissue culture process of plants. It is hypothesised that the tissue culture process restores juvenile characteristics to explants obtained from physiologically mature mother-plants. Also, restoration of juvenile characters in mature mother plants is believed to be helpful for in vitro regeneration, especially for recalcitrant woody perennials. However, the above hypothesis has not been tested using molecular biological techniques. Profiling microRNAs related to phase change can provide us with an indication of the maturity stage (greater juvenility if less mature) of in vitro cultured plants. MicroRNAs are a group of non-coding small RNAs of 21-22 nucleotides, highly conserved across many plant species and they play a key regulatory role in plant development, either by directing cleavage of complimentary mRNAs or by translational inhibition. The current study looked at two microRNAs involved in the juvenile-to-adult phase change; miR156, which supresses miR172 and is a marker for juvenility, and miR172, which promotes maturation and reproductive transition in plants. The two microRNAs were profiled from shoot tips of in vitro shoots of mature avocado. Relative expression of miR156 was significantly reduced after both 7 days and 3 months in culture compared to basal expression. Also, miR156 expression was significantly reduced from 3 to 6 months. Interestingly, miR172 expression significantly decreased more than five-fold after 7 days of culture, and remained low at 3 and 6 months. The rapid reduction in miR172 expression suggests that mature avocado tissues may downregulate miR172-regulated phase-change pathways during in vitro culture, possibly maintaining a prolonged juvenile state. This study provides the first molecular indication of physiologically mature avocado material regaining juvenility characteristics as a result of the tissue culture process.
Jayeni Chathurika Amarathunga Hiti Bandaralage won an ISHS student award for the best oral presentation at the International Symposia on Tropical and Temperate Horticulture in Australia in November 2016.
Jayeni Chathurika Amarathunga Hiti Bandaralage, Queensland Alliance for Agriculture and Food Innovation (QAAFI), Level 3, Queensland Bio-science Precinct, Building no 80, The University of Queensland, St Lucia 4072, Queensland, Australia, e-mail: firstname.lastname@example.org