*3.4. Chromosome Distribution of the PebHLHs*

The chromosome distribution of each *PebHLH* was obtained, as shown in Figure 3. The total 117 *PebHLHs* were located on nine chromosomes. Seven members were located at unknown chromosomal positions. Among them, Chr1 contained the largest distribution of 41 *PebHLH* genes (~37.27%), followed by Chr6 (24 genes, ~21.82%). Meanwhile, Chr9 distributed the least number of *PebHLH* genes (3 genes, ~2.73%). Chr2, Chr3, Chr4, Chr5, Chr7, and Chr8 presented 7, 6, 10, 5, 4, and 10 *PebHLH* genes, respectively.

**Figure 2.** Phylogenetic clustering, conserved motifs, and exon/intron organization of *PebHLHs*. Ten color boxes indicate different motifs, green color represents 5 and 3 UTR, and yellow color and black lines represent exons and introns, respectively.

**Figure 3.** Locations of the 117 identified *PebHLH*s in 9 chromosomes of Passion fruit. The *PebHLHs* were located on No. 1, 2, 3, 4, 5, 6, 7, 8, and 9 chromosomes.

#### *3.5. Promoter Analysis of PebHLH Genes*

The TATA and CAAT boxes were the key cis-regulatory elements, which were found in all 117 *PebHLHs* (Figure 4). Additionally, the promoter region of the *PebHLH* family contains a large number of action elements related to abiotic stress, such as the cold-responsive element (CCGAAA) and the salicylic acid-responsive element (CCATCTTTTT and TCAGAA-GAGG). Some cis-acting elements are associated with stress response, such as the woundresponsive element (AAATTTCCT). In addition, there are some hormone-related elements, such as the abscisic acid responsiveness element (ABRE, GACACGTGGC, and ACGTG), the MeJA-responsive motifs (TGACG and CGTCA), the gibberellin-responsive motifs (CCTTTTG, TATCCCA, and TCTGTTG), and the auxin-responsive element (AACGAC).
