| Summary: | <i>Ambrosia artemisiifolia</i> is a noxious invasive alien weed, that is harmful to the environment and human health. <i>Ophraella communa</i> is a biocontrol agent for <i>A. artemisiifolia,</i> that was accidentally introduced to the Chinese mainland and has now spread throughout southern China. Recently, we found that upon artificial introduction, <i>O. communa</i> can survive in northern China as well. Therefore, it is necessary to study the cold hardiness of <i>O. communa</i>. Many genes have been identified to play a role in cold-tolerance regulation in insects, but the function of the gene encoding non-muscle myosin regulatory light chain (<i>MRLC-sqh</i>) remains unknown. To evaluate the role played by <i>MRLC-sqh</i> in the cold-tolerance response, we cloned and characterized <i>MRLC-sqh</i> from <i>O. communa</i>. Quantitative real-time PCR revealed that <i>MRLC-sqh</i> was expressed at high levels in the gut and pupae of <i>O. communa</i>. The expression of <i>MRLC-sqh</i> was shown to decrease after cold shock between 10 and 0 °C and ascend between 0 and −10 °C, but these did not show a positive association between <i>MRLC-sqh</i> expression and cold stress. Silencing of <i>MRLC-sqh</i> using ds<i>MRLC-sqh</i> increased the chill-coma recovery time of these beetles, suggesting that cold hardiness was reduced in its absence. These results suggest that the cold hardiness of <i>O. communa</i> may be partly regulated by <i>MRLC-sqh</i>. Our findings highlight the importance of motor proteins in mediating the cold response in insects.
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