Many microRNAs (miRNAs) have been predicted from small RNA sequencing data, but little was experimentally verified due to the lack of effective methods. Here, we developed a simple and reliable dual gene expression cassette vector-based method to verify predicted plant miRNAs. We cloned osa-miR528 as a known miRNA, hvu-miRX as a predicted miRNA and TaDREB3 open reading frame as a non-miRNA into the first gene expression cassette and fused their complementary or noncomplementary sequences as predicted target or nontarget sequences with the 3ʹ untranslated region of green fluorescent protein (GFP) in the second one. When these constructs were bombarded into plant cells, only the construct containing both osa-miR528 or hvu-miRX and its complementary sequence did not generate green fluorescence. Stem-loop reverse-transcription polymerase chain reaction detected mature osa-miR528 or mature hvu-miRX in the cells, while northern analysis showed that GFP messenger RNA from the construct containing both osa-miR528 or hvu-miRX and its complementary sequence was degraded. Taken together, the results indicate that hvu-miRX is an authentic miRNA like osa-miR528, miRNA's complementary sequence is its target sequence, and both osa-miR528 and hvu-miRX silenced the GFP expression via a cleavage mode. Our method thus facilitates the verification of predicted plant miRNAs, target sequences, and function modes. K E Y W O R D S bombardment, cleavage mode, dual gene expression cassette vector, fluorescence, green fluorescent protein, miRNA, target sequence 1 | INTRODUCTION MicroRNAs (miRNAs) are endogenous and single-stranded small RNAs (sRNAs) with the size of 20-24 nucleotides (nt). In animals, they are generated from hairpin precursors (pre-miRNAs) in the cytoplasm by Dicer, a class 3 ribonuclease III enzyme. Pre-miRNAs are generated from primary transcripts (pri-miRNAs) in the nucleus by Drosha, a class 2 ribonuclease III enzyme. In plants, both miRNAs and their hairpin pre-miRNAs are generated in the nucleus by one Dicer homolog, called Dicer-like 1 (DCL1) (Jones-Rhoades et al., 2006). Either animal pri-miRNAs or plant pri-miRNAs are most transcribed from genomic DNA by RNA polymerase II (Y. Lee et al., 2004). Only a small group associated with Alu repeats are transcribed by RNA polymerase III (Borchert et al., 2006). Plant miRNA genes are usually present as individual entities scattered around the intergenic regions. Apart from the above dominant canonical biogenesis pathway, noncanonical pathways of miRNA biogenesis such as Drosha-independent and Dicer independent pathways were also present. An example is mirtrons that are produced from the introns of mRNA during splicing (Ruby et al., 2007). Mirtron biogenesis has not been extensively documented in plants.So far only 5 and 18 putative mirtrons were found in Arabidopsis and rice, respectively (Meng & Shao, 2012). miRNAs function as a gene regulator via an RNA-induced silencing complex (RISC), which contains an argonaute (AGO) protein and other associated proteins.Overall, one m...