**4.1. lncRNA as target mimics of miRNA**

Target mimicry is a mechanism of lncRNA for regulating the functions of miRNAs. They inhibit the interaction between the miRNA and their respective targets by binding to the target of miRNA via partial complementary sequence [46]. The novel mechanism of target mimicry was first discovered in *Arabidopsis*. In addition, *phosphate Starvation 1* (*IPS1*) was the first lncRNA identified as endogenous target mimic (eTM) of miR399 involved in phosphate homeostasis [46]. During phosphate starvation, the expression of miR399 is induced in companion cells and phloem [47]. Subsequently, the expression of *PHO2* gene, a target of miR399, is repressed [47–50]. This gene encodes UBC24 (E2 ubiquitin conjugase-related enzyme) and the reduction in its expression leads to the increased expression of *Pht1;8* and *Pht1;9* (phosphate transporter genes) in roots [47, 48]. Later, a similar mechanism was discovered in animals and humans suggesting target mimicry as the prevalent phenomenon [51, 52].

## **4.2. Histone modification**

The lncRNAs are known to regulate gene expression through epigenetic changes. These epigenetic changes may result in alteration of gene expression in plants. Vernalization is the most common phenomenon of lncRNA mediated epigenetic regulation in plants. In *Arabidopsis*, FLOWERING LOCUS C (FLC) gene is the principal regulator of vernalization process and regulates the flowering time [53]. The expression of this gene is regulated by *COOLAIR* and *COLDAIR* lncRNAs through histone modifications [54].
