**3. Classification of non-coding RNAs**

The major category of grouping non-coding RNAs is based on their origin, nature of biogenesis, as well as based on its mechanism of action. The non-coding RNA transcripts can either perform housekeeping or regulatory functions. Those non-coding RNAs dynamically involved in cellular and ribosomal functions include tRNAs, snRNAs, rRNAs, and snoRNAs, whereas the regulatory ncRNAs are actively involved in most of the plant growth and development processes dealing with biotic and abiotic stress responses and plant immunity [16]*.* These regulatory ncRNAs, such as miRNAs, piRNAs, siRNAs, and lncRNAs, are transcribed from DNA and are primarily involved in transcriptional and post-transcriptional gene regulations [17]. The basic classification of ncRNA is presented in **Tables 2** and **3** described the brief details about the ncRNA. These regulatory ncRNAs cannot generally transcribe into proteins whereas housekeeping ncRNAs assist in protein translation [18].


#### **Table 1.**

*List of ncRNA and their brief history.*

**Table 2.** *Classification of ncRNA.*
