**5. Conclusions**

In the present study, 24 *Hsf* genes and 117 *Hsp* genes (including *sHsp*, *Hsp60*, *Hsp70* and *Hsp100*) were identified from the eggplant genome. The phylogeny, gene structure, expression profiles and heat stress responses of these genes were analyzed. The total number of *Hsf* and *Hsp* genes of eggplant was similar to that of Arabidopsis, tomato and rice, covering all the subfamilies, and the gene structure and motif composition were relatively stable and conserved in the evolutionary process. *SmHsf* genes, as key transcriptional activators of *Hsp* genes, regulated different subfamilies of *Hsps* in eggplant. Most of *Hsf* and *Hsp* genes are highly induced by HS in eggplant leaves, which indicated these genes participate in the response to heat stress. The expression levels of these genes in the thermotolerant line were enhanced significantly higher than those of in the thermosensitive line under HS in eggplant, which may be the main reason for strong thermotolerance in thermotolerant eggplant. According to the above results, it is expected to evaluate the thermotolerance of different eggplant resources by analyzing the expression change of specific *Hsf* and *Hsp* genes under HS and even the thermotolerance of other solanaceae species resources. The present study was undertaken to establish a solid

foundation for functional research on the eggplant *Hsf* and *Hsp* gene families and broaden our understanding of the mechanism of thermotolerance mediated by *Hsf* and *Hsp* genes in solanaceous plants.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/ 10.3390/horticulturae7060149/s1, Table S1: *Hsf* and *Hsp* gene families in eggplant. Table S2: Phylogenetic analysis of Hsf proteins in eggplant, Arabidopsis, and tomato. Table S3: Phylogenetic analysis of sHsp proteins in eggplant, Arabidopsis, and tomato. Table S4: Phylogenetic analysis of Hsp60 proteins in eggplant, Arabidopsis, and tomato. Table S5: Phylogenetic analysis of Hsp70 proteins in eggplant, Arabidopsis, and tomato. Table S6: Phylogenetic analysis of Hsp90 proteins in eggplant, Arabidopsis, and tomato. Table S7: Phylogenetic analysis of Hsp100 proteins in eggplant, Arabidopsis, and tomato. Table S8: Sequence logos for the conserved motifs of Hsf proteins in Arabidopsis and eggplant. Table S9: Sequence logos for the conserved motifs of sHsp proteins in Arabidopsis and eggplant. Table S10: Sequence logos for the conserved motifs of Hsp60 proteins in Arabidopsis and eggplant. Table S11: Sequence logos for the conserved motifs of Hsp70 proteins in Arabidopsis and eggplant. Table S12: Sequence logos for the conserved motifs of Hsp90 proteins in Arabidopsis and eggplant. Table S13: Sequence logos for the conserved motifs of Hsp100 proteins in Arabidopsis and eggplant. Table S14: Primers used in qRT-PCR analysis.

**Author Contributions:** Conceptualization, B.S.; methodology, G.S.; software, R.C.; validation, C.G., G.S. and B.S.; formal analysis, B.S.; investigation, Q.P.; resources, Z.L. (Zhiliang Li) and Z.L. (Zhenxing Li); data curation, Q.P.; writing—original draft preparation, C.G. and Q.P.; writing—review and editing, C.G., B.S. and G.S.; visualization, G.S.; supervision, B.S.; project administration, Z.L.; funding acquisition, C.G. and B.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Natural Science Foundation of China, grant number 31801875, the Natural Science Foundation of Guangdong Province, grant number 2020A1515011168, the Department of agriculture and rural areas of Guangdong province of China, grant number 2018KCZX06, 2020KJ106 and 2020KJ110 and the Special fund for scientific innovation strategyconstruction of high level Academy of Agriculture Science, grant number R2019PY-QF009, R2018QD-040.

**Data Availability Statement:** The data supporting the findings of this study are available from the corresponding author upon reasonable request.

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