Editorial (2015)

In the past decade, the discovery of noncoding RNAs (ncRNAs), particularly microRNAs (miRNAs), has advanced plant biotechnology. The large diversity of ncRNAs, dsRNAs, miRNAs, siRNAs and long ncRNAs has become excellent targets for functional studies in plant biology and has found biotechnology applications. MiRNAs are universal gene regulators and play important functions in plant biological and metabolic processes, including flower development and phase change, as well as plant responses to both biotic and abiotic environmental stresses (Zhang and Wang, 2015). Thus, expression patterns of miRNAs result in phenotypes of interest; changes in expression of a single miRNA can significantly increase plant biomass or increase resistance to abiotic stress. In this focus issue, leading experts summarize major discoveries and advances in this field. Hong and Jackson (2015) review the function of miRNAs in floral induction and development, an important biological process that affects crop yield. Several miRNAs, including miR156 and miR172, post-transcriptionally regulate genes involved flower development including juvenile to adult transition and initiation of floral organs (Hong and Jackson, 2015). Ferdous et al. (2015) review the function of miRNAs when plants are exposed to water stress (Ferdous, et al., 2015). Important to crop improvement, plants have evolved miRNA-mediated gene regulation mechanisms controlling their responses to water stress. Zheng and Qu (2015) review the potential application of miRNAs in improving agronomic traits in rice by manipulating miRNAs. Recently, long ncRNAs have been used for crop improvement. Therefore, Chua and his colleagues review identification, classification, regulatory function and biotechnological potential of long ncRNAs in crop improvement (Liu et al., 2015). To that end, Molnar (2015) reviews the importance of mobility of miRNAs in gene silencing. In addition to these review articles, this focus issue also includes several exciting original contributions. Using high-throughput deep-sequencing technology, Xie et al. (2015) identified 65 conserved miRNA families from cotton, many of which are differentially expressed during cotton fibre initiation and differentiation (Xie et al., 2015). The same group also studied the evolution and expression profile of miRNAs during plant polyploidization (Xie and Zhang, 2015). Gao et al. (2015) show that miRNAs may regulate ethylene to control tomato fruit development (Gao et al., 2014). Two other original contributions explore the use of miRNAs in metabolic engineering and regulation of biotic/abiotic stress. Boke et al. (2015) investigated the role of miRNAs in alkaloid biosynthesis in opium poppy to identify potential biotechnology targets. Zeng (2015) performed deep sequencing to identify RNAs potentially involved in salinity stress in a halophytic plant. Finally, Daniell and colleagues (Jin et al., 2015) expressed dsRNA for three target genes via the chloroplast genome for the first time to study RNA interference in intended hosts; they achieved almost complete silencing of target genes in the insect gut after feeding transplastomic leaves to target insects. This opens the door to use the chloroplast genome for high-level expression of dsRNA to confer desired agronomic traits or various biomedical applications to down-regulate dysfunctional genes in cancer or autoimmune disorders. The editors trust that this focus issue on ncRNA will be educational in further advancing research on this important topic.