Cold stress responsive microRNAs and their targets in Musa balbisiana

Cold stress is an environmental factor affecting plant development and production. Recently,micro RNAs(mi RNAs) have been found to be involved in several plant processes such as growth regulation and stress responses. Although mi RNAs and their targets have been identified in several banana species, their participation during cold accumulation in banana remains unknown. In this study, two small RNA libraries were generated from micropropagated plantlets of Musa balbisiana grown at normal and low temperature(5°C).A total of 69 known mi RNAs and 32 putative novel mi RNAs were detected in the libraries by Solexa sequencing. Sixty-four cold-inducible mi RNAs were identified through differentially expressed mi RNAs analysis. Among 43 mi RNAs belonging to 26 conserved mi RNA families with altered expression, 18 were upregulated and 25 downregulated under cold stress. Of21 putative novel mi RNAs with altered expression, four were downregulated and 17 upregulated. Furthermore,eight mi RNAs were validated by stem-loop q RT-PCR and their dynamic differential expression was analyzed. In addition, 393 target genes of 58 identified cold-responsive mi RNAs were predicted and categorized by function.These results provide important information for further characterization and functional analysis of cold-responsive mi RNAs in banana.

Cold stress is an environmental factor affecting plant development and production. Recently, microRNAs (miRNAs) have been found to be involved in several plant processes such as growth regulation and stress responses. Although miRNAs and their targets have been identified in several banana species, their participation during cold accumulation in banana remains unknown. In this study, two small RNA libraries were generated from micropropagated plantlets of Musa balbisiana grown at normal and low temperature (5 degrees C). A total of 69 known miRNAs and 32 putative novel miRNAs were detected in the libraries by Solexa sequencing. Sixty-four cold-inducible miRNAs were identified through differentially expressed miRNAs analysis. Among 43 miRNAs belonging to 26 conserved miRNA families with altered expression, 18 were upregulated and 25 downregulated under cold stress. Of 21 putative novel miRNAs with altered expression, four were downregulated and 17 upregulated. Furthermore, eight miRNAs were validated by stem-loop qRT-PCR and their dynamic differential expression was analyzed. In addition, 393 target genes of 58 identified cold-responsive miRNAs were predicted and categorized by function. These results provide important information for further characterization and functional analysis of cold-responsive miRNAs in banana.