Abstract
Development and fitness of any organism rely on properly controlled gene expression. This is especially true for plants, as their development is determined by both internal and external cues. MicroRNAs (miRNAs) are embedded in the genetic cascades that integrate and translate those cues into developmental programs. miRNAs negatively regulate their target genes mainly post-transcriptionally through two co-existing mechanisms; mRNA cleavage and translational inhibition. It is unclear whether the efficiency of miRNA-guided regulation is generally influenced by factors like ambient temperature or developmental stage. Here we show that plant miRNA accumulation and their mode of action can be temperature- and development-sensitive. Higher temperatures tend to induce a more pronounced accumulation of mature miRNAs. Both parameters have also an impact on the expression patterns of the core players involved in miRNA performance. We show that efficiency of miRNA-mediated gene silencing declines with age during vegetative development in a temperature-dependent manner. Co-existence of cleavage and translational inhibition was also found to be dependent on temperature and developmental stage. Therefore, each miRNA family specifically regulates their respective targets, while temperature and growth influence the performance of miRNA-dependent regulation in a more general way.
