**5. Conclusions**

Trihelix transcription factors participate in many plant biological processes but have not been systematically studied. Here, 41 rice trihelix transcription factors were identified by bioinformatics analysis. Gene synteny analysis showed that *OsMSL*s are less conserved, and most genes may not originate from the same ancestor. Phylogenetic analysis categorized them into five subfamilies. The gene structures and conserved functional domains of the rice trihelix transcription factors varied greatly but they shared five cis-elements governing light dehydration stress responses. Expression pattern analysis revealed that the trihelix transcription factors had the highest expression levels in the early rice growth stages and most of the strongly upregulated genes were localized in the leaves and sheaths. Real-time quantitative PCR analysis of the trihelix family genes subjected to various stressors or ABA revealed that they were induced in response to drought, high salt, hydrogen peroxide, and ABA. However, these responses were also regulated by light and individual *OsMSL* expressions differed with the presence or absence of light. Our study helped elucidate the biological functions of the trihelix transcription factors in rice.

**Supplementary Materials:** Supplementary materials can be found at http://www.mdpi.com/1422-0067/20/2/ 251/s1.

**Author Contributions:** Conceptualization, J.L.; data curation, X.M.; formal analysis, J.S.; funding acquisition, D.Z.; investigation, J.W. (Jing Wang) and J.W. (Jingguo Wang); project administration, H.Z. (Hongwei Zhao); resources, H.Z. (Hualong Liu); software, H.Z. (Hongliang Zheng); supervision, Z.Z.; writing—original draft, J.L.; Writing—review & editing, M.Z. All authors read and approved the final manuscript.

**Funding:** This research was funded by 1. National Science and Technology Major Project (2018ZX0800912B-002). 2. Youth Science Foundation of Heilongjiang Province (QC2017015). 3. National Natural Science Foundation (31701507). 4. Natural Science Foundation of Heilongjiang Province of China (No. C2015003).

**Acknowledgments:** We thank Editage for its linguistic assistance during the preparation of this manuscript.

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