Fig. 3

Biological function analysis of GhBPE. A Amino acid alignment of BPE proteins in various plant species. The black line above the sequence indicates the bHLH domain. B Phylogeny of the bHLH family genes in different species. The bootstrap values shown indicate the robustness of each branch. The scale bar corresponds to 0.05 substitutions per site. Amino acid sequences were used for the amino acid alignment and phylogeny analysis. AtBPEp (NP_849829.1) Arabidopsis thaliana; AtBPEub (NP_564749.1) Arabidopsis thaliana; LsbHLH094-like (XP_023740329.1) Lactuca sativa; HabHLH094 (XP_021973982.1) Helianthus annuus; TobHLH (PON53727.1) Trema orientale; PabHLH (PON67443.1) Parasponia andersonii; MeBHLH089-like (XP_021616639.1) Manihot esculenta; and CcBHLH79 (XP_020238985.1) Cajanus cajan. C Subcellular localization of GhBPE in tobacco leaves. GhBPE fused with GFP or GFP was transformed into tobacco leaves. Nuclei are represented by RFP-NLS. Merged images show the co-localization of NLS and GFP signals. Scale bar = 50 μm. D Transcription activation activity analysis of GhBPE. The vector pGADT7-largeT/pGBKT7-p53 and pGADT7-largeT/pGBKT7-laminC were transformed into yeast cells and used as negative and positive controls, respectively. The yeast strains were grown on SD/-Leu/-Trp, SD/-Leu/-Trp/-His, and SD/-Leu/-Trp/-His+X-α-gal solid media. E The transcriptional activity of GhBPE was analyzed using a dual-luciferase assay. The empty pBS vector, reporter and internal control vector were co-transformed as a control. The experimental results are conveyed using the mean ± SD of three biological replicates. Tukey’s HSD: * P < 0.05, ** P < 0.01