MicroRNAs regulated cell differentiation in plants: Case Study

MicroRNAs (miRNAs) the gene expression by base-pairing with the transcripts of their targets, leading to posttranscriptional gene silencing and down-regulation of the target genes (Ross and Davis 2011, Vashisht and Nodine 2014, Wang, et al. 2011a). Different expression of miRNAs is associated with many human diseases and has been shown to affect the hallmarks of cancer through regulating proliferative signaling, resisting cell death, evading growth suppressors, enabling replicative immortality, and activating metastasis (Duggal, et al. 2012, Ross and Davis 2011). Recent evidence suggests that nutrients and dietary factors modify miRNA expression and their mRNA targets through cell cycle regulation, differentiation, and stress response (Duggal, et al. 2012, Ross and Davis 2011). Resveratrol (3,5,4'-trihydroxystilbene) is a plant phenolic phytoalexin that has been reported to have antitumor properties by exerting anti-proliferative effects against A549 human non-small cell lung cancer cells (Bae, et al. 2011, Lancon, et al. 2012). Results from microarray analysis demonstrated that resveratrol treatment altered miRNA and its target gene expression and lead to changes of cell proliferation and differentiation, indicating that the effects of resveratrol on microRNA populations in humans may present a novel approach for studying the anticancer mechanisms, metabolism, and muscle differentiation (Bae, et al. 2011, Lancon, et al. 2012).

 Plant miRNAs have been reported to play important roles in developmental control, hormone secretion, cell differentiation, and response to environmental stresses (Borges, et al. 2011, Liu, et al. 2012, Vashisht and Nodine 2014, Wang, et al. 2011a). In Arabidopsis, complementary sites within predicted targets identified with near complementarity are conserved in rice and most of the targets are members of transcription factor gene families involved in developmental patterning, suggesting that many plant miRNAs act similarly to small interfering RNAs in directing mRNA cleavage and many plant miRNAs function during cellular differentiation to clear key regulatory transcripts (Rhoades, et al. 2002, Wang, et al. 2011a, Zhang, et al. 2009). An online database for Arabidopsis thaliana miRNA function annotations that integrated miRNA-target interactions, transcription factor and their targets, expression profiles, genomic annotations, and pathways has been developed and the associated terms may provide valuable insight for the functions of each miRNA (Liu, et al. 2012). 

Regulatory activations of miRNAs in development of plant embryos, proliferation of plant stem cells, modulation of immune response to macrophages, and development of plant male germ line have been well documented (Borges, et al. 2011, Dweep, et al. 2013, Vashisht and Nodine 2014, Wang, et al. 2011a). Compared to targets of animal miRNAs, targets of plant miRNAs can be easily identified by computational prediction because plant miRNAs always bind their targets with near perfect complementarity (Dweep, et al. 2013, Liu, et al. 2012). Recently, great progress of regulatory activations of miRNAs in plant cell differentiation has been made (Borges, et al. 2011, Dweep, et al. 2013, Vashisht and Nodine 2014,). In this review, we have focused miRNA expression and its potential role in regulating cell differentiation in Arabidopsis and summarized the miRNAs regulated cell differentiation during root, shoot, leave, and embryo development based on the previously published investigations (Table 1). We have further described practical application of expression of miRNAs in plant molecular breeding.