AUTHOR=Liu Yao , Sang Xuelian , Liu Liqin , Ren Ci , Zhang Zhixin , Chen Tao , Li Hongli , Jue Dengwei , Shi Shengyou 
  
TITLE=Whole genome identification and operational analysis of the bHLH gene family in longan and the role of DlbHLH8 in flowering regulation
  
JOURNAL=Frontiers in Plant Science
  
VOLUME=Volume 17 - 2026
  
YEAR=2026
  
URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2026.1824280
  
DOI=10.3389/fpls.2026.1824280
  
ISSN=1664-462X
  
ABSTRACT=BackgroundLongan (Dimocarpus longan Lour.) is an important tropical and subtropical fruiting crop; understanding its flower formation regulatory mechanisms represents an important direction in floral growth and evolution research. The basic helix-loop-helix (bHLH) transcription factor family plays crucial roles in diverse physiological processes in plants, including growth, development, and stress responses. However, the roles of bHLH genes in longan flower development have not been investigated.ResultsWe detected 126 bHLH family members in the longan genome database. The bHLH genes of longan and Arabidopsis were further classified into 27 subfamilies. Structural analysis indicated that DlbHLH proteins were comparatively well-conserved within specific subfamilies. The results of collinearity analysis, supported by Ka/Ks (Non-synonymous substitution rate/Synonymous substitution rate) analysis, indicated that the expansion of the DlbHLH gene family was primarily driven by segmental duplication followed by strong purifying selection. Examination of the promoter regions of the DlbHLH gene family suggested that DlbHLH participated in the control of floral bud development. bHLH family genes exhibited diverse distinct expression profiles during the flowering processes of the varieties “Shixia” and “Sijimi” (SJ), with DlbHLH8 exhibiting a dynamic and cultivar-specific expression pattern, including a 7.49-fold reduction in expression during the critical T1-T2 phase of flower development in the SJ variety. Phenotypic observations revealed that under long-day circumstances, genetically modified Arabidopsis plants overexpressing DlbHLH8 exhibited significantly earlier flowering than wild-type plants. Gene expression analysis showed that DlbHLH8 overexpression was associated with the altered expression of key genes in the flowering pathway, namely AtAP1 (Arabidopsis thaliana APETALA1), AtLFY (Arabidopsis thaliana LEAFY), and AtFLC (Arabidopsis thaliana FLOWERING LOCUS C). These findings offer a basis for additional research into the regulatory mechanisms of bHLH proteins in longan flower development.ConclusionSome DlbHLH family members play important roles in the regulation of plant flowering; DlbHLH8 may promote plant flowering in longan by regulating AtAP1, AtLFY, and AtFLC.