Characterization and Expression Analysis of the bHLH Gene Family During Developmental Stages and Under Various Abiotic Stresses in Sanghuangporus baumii

Background: Basic helix–loop–helix (bHLH) transcription factors (TFs) widely exist in eukaryotic organisms and play a key role in plant growth and development in response to environmental stresses.Sanghuangporus baumii, an important medicinal mushroom known for its anticancer properties, has limited research on the bHLH gene family. Methods: This research utilized the genomic data fromS. baumiito identify bHLH family members, and their gene structure, conserved motifs, and phylogenetic relationship were characterized. Additionally, we conducted an analysis of promoter cis-elements and predicted protein interaction networks. We also examined the expression profiles of bHLH genes during different developmental stages and in response to four abiotic stresses: heat, cold, oxidative stress, and heavy metal exposure. Finally, we overexpressed the candidate geneSbbHLH3in yeast to assess its tolerance to these different stress conditions. Results: A total of 12SbbHLHgenes were identified inS. baumii, and the members of the bHLH gene family displayed a variety of physicochemical characteristics, reflecting their diverse array of functions. Based on homology, the SbbHLH proteins are more closely related to those found inLentinula edodesandPleurotus ostreatus. The analysis of promoter cis-elements showed thatSbbHLHs contain several elements associated with abiotic stress response, and a network prediction identified 28 bHLH-interacting proteins. Expression pattern analysis revealed that mostSbbHLHgenes exhibited a positive response to different developmental stages and abiotic stresses. Notably, the overexpression ofSbbHLH3significantly enhanced stress tolerance in yeast. Conclusions: This study provides a comprehensive assessment of the bHLH family inS. baumii, delivering new genetic resources for breeding resistant varieties.