The functions of long noncoding RNAs in plants

Noncoding RNAs are emerging as major regulators in plant development and environmental response. MicroRNAs, small RNAs, and ribosomal RNAs have established mechanisms for generation, maturation, and function. However, long noncoding RNAs (lncRNAs) currently lack a robust classification according to their function. lncRNAs are here defined as noncoding RNAs that are longer than 200 nucleotides and generally transcribed by RNA polymerase II. They often exhibit low expression and limited sequence conservation yet display tissue or stress-specific regulation. Furthermore, lncRNAs are categorized based on their location relative to nearby genes, including sense (overlapping a gene on the same strand), antisense (overlapping on the opposite strand), intronic (located within intron), intergenic (found between genes), and bidirectional (transcribed in the opposite direction from a nearby gene). Here, we summarized the last years of work in the field of lncRNA, but instead of grouping them into the biological processes they are involved in, we attempt to group them into general functions in plants. This will not be an exhaustive grouping of known functions for lncRNA, rather a list of established functions with several characterized cases.