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To adapt and sense environmental perturbations, including a variety of biotic and abiotic stress conditions, plants have developed disparate regulatory pathways. Mitogen-activated protein kinase (MAPK or MPK) signaling cascades are found widespread across the eukaryotic kingdoms of life. In plants, they may regulate signaling pathways aimed at resisting the stressful effects of low temperature, salt damage, drought, touch, and mechanical damage. To date, no conclusive studies into <i>Liriodendron chinense</i> (Hemsl.) Sarg MPK-related stress resistance signaling have been performed. In our study, we cloned three homologous <i>L. chinense</i> MAP kinase kinase family genes: <i>LcMKK2</i>, <i>LcMKK4</i>, and <i>LcMKK6</i>. <i>LcMKK2</i> and <i>LcMKK6</i> have their highest expression level in the root, while <i>LcMKK4</i> is highly expressed in the stem. <i>LcMKK2</i> showed upregulation in response to salt and cold stress conditions in <i>L. chinense</i>. To further analyze its gene function, we overexpressed <i>LcMKK2</i> in wild-type <i>Arabidopsis thaliana</i> (L.) Heynh. and obtained transgenic plants. Overexpression of <i>LcMKK2</i> caused a significant reduction in plant mortality (from 96% to 70%) in response to a 7-day 200 mM NaCl treatment. Therefore, we conclude that <i>LcMKK2</i> is involved in a signaling response to salt stress, and it could thus prove an effective target gene for breeding strategies to improve <i>Liriodendron</i> salt tolerance.