**5. Conclusions**

In conclusion, a total of 24 *Dof* genes were identified from physic nut, and these *Dof* genes were further divided into three major groups based on the phylogenetic inference. The gene structures, conserved motifs, gene duplicated events, selection pressures, and expression profiling of these *JcDof* genes were analyzed. A genome comparison discovered that the expansion of the *Dof* gene family in physic nut mainly resulted from segmental duplication, and this expansion was mainly subjected to positive selection. The expression profile demonstrated the broad involvement of *JcDof* genes in different hormonalor abiotic stressed treatments. Among them, three genes (*JcDof-1*, *JcDof-8*, and *JcDof-10*) exhibited significant responses to the BA treatment. Furthermore, many *JcDof* genes were significantly responsive to the salt and drought treatments. On the whole, this study provides an extensive resource for understanding the *Dof* genes in physic nut.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1422-0067/19/6/1598/ s1.

**Author Contributions:** C.L. conceived and supervised this study. C.L. and P.W. designed the experiments. P.W. carried out the experiments, and analyzed and interpreted the data. J.L., X.G., D.Z. and A.L. participated in the discussion and provided valuable advice and practical contributions. C.L., P.W. and J.L. wrote the manuscript. All authors reviewed, edited, and approved the final manuscript.

**Acknowledgments:** This work was supported by the following grants: National Natural Science Foundation of China (grant nos. 31471220, 91440113), Start-up Fund from Xishuangbanna Tropical Botanical Garden, and 'Top Talents Program in Science and Technology' from Yunnan Province.

**Conflicts of Interest:** The authors declare no conflict of interest.
