Biotechnology approaches using recombinant DNA and transgenic technologies are effective strategies for plant genetic improvement and have been successfully adopted in various crop species. Their use for trait modification in switchgrass has also been demonstrated (Somleva et al. 2008; Chuck et al. 2011; Fu et al. 2011; Xu et al. 2011; Fu et al. 2012) and are expected to play an increasingly important role in switchgrass genetic improvement. However, they can also raise serious ecological concerns because of the possibility of transgene escape (Scott and Wilkinson 1999; Koivu et al. 2001). To address these concerns, various molecular strategies have been developed for gene containment by altering different biological pathways impacting plant flowering (Koivu et al. 2001; Daniell 2002). Genetic engineering of male sterility for controlling pollen grain movement is one of the most important measures for preventing gene flow. In recent years, with the increasing knowledge of miRNAs, genetic manipulation of miRNAs and their targets in transgenic plants could also be one of the useful strategies for inducing male sterility.

MiR159 is a conserved miRNA and negatively regulates the expression of GAMYB genes (Achard et al. 2004; Millar et al. 2005; Tsuji et al. 2006; Alonso-Peral et al. 2010). It has been reported that GAMYB genes are predominantly expressed in the anthers both in rice and Arabidopsis (Millar et al. 2005; Tsuji et al. 2006). Transgenic Arabidopsis overexpressing miR159 causes anther defects (male sterility) due to the down-regulation of its targets, AtMYB33 and AtMYB65 (Achard et al. 2004; Alonso-Peral et al. 2010). Similarly, overexpression of miR159 in rice results in flower malformation and male sterility by decreased expression of OsGAMYB (Tsuji et al. 2006). Recently, Wang et al. (2012) reported that overexpression of the wheat miR159, TamiR159, resulted in delayed heading time and male sterility in transgenic rice plants. We also cloned a switchgrass miR164 (Pvi-miR164a) precursor by PCR based on its EST sequence, and found that overexpression of the Pvi-miR164a precursor driven by the rice Actin promoter led to semi-dwarf and male sterility in transgenic rice plants (Li et al. unpublished). These data suggest the great potential of miRNAs and their target genes for use in switchgrass to induce male sterility as an effective strategy for preventing transgene escape.