Oligo—Not Only for Silencing: Overlooked Potential for Multidirectional Action in Plants

Oligo technology is a low-cost and easy-to-implement method for direct manipulation of gene activity. The major advantage of this method is that gene expression can be changed without requiring stable transformation. Oligo technology is mainly used for animal cells. However, the use of oligos in plants seems to be even easier. The oligo effect could be similar to that induced by endogenous miRNAs. In general, the action of exogenously introduced nucleic acids (Oligo) can be divided into a direct interaction with nucleic acids (genomic DNA, hnRNA, transcript) and an indirect interaction via the induction of processes regulating gene expression (at the transcriptional and translational levels) involving regulatory proteins using endogenous cellular mechanisms. Presumed mechanisms of oligonucleotides’ action in plant cells (including differences from animal cells) are described in this review. Basic principles of oligo action in plants that allow bidirectional changes in gene activity and even those that lead to heritable epigenetic changes in gene expression are presented. The effect of oligos is related to the target sequence at which they are directed. This paper also compares different delivery methods and provides a quick guide to using IT tools to help design oligonucleotides.