Expression profiles of four / homologous genes encoding bHLH transcription factors in .

bHLH-type transcription factors-BRASSINOSTEROID INSENSITIVE 1-EMS-SUPPRESSOR 1 (BES1) and BRASSINAZOLE RESISTANT 1 (BZR1)-play key roles in brassinosteroid (BR) signaling. By contrast, the functions of the other four BES1/BZR1 homologs (BEH1-4) remain unknown. Here, we describe the detailed expression profiles of the / family genes. Their expressions were distinct regarding growth-stage dependence and organ specificity but exhibited some overlaps as well. Furthermore, their mRNA levels mostly remained unchanged responding to seven non-BR phytohormones. However, and were downregulated by brassinolide, suggesting a close association with the BR function. Additionally, was ubiquitously expressed throughout the life of the plant but displayed some expression preference. For instance, expression was limited to guard cells and the adjacent pavement cells in the leaf epidermis and was induced during growth progression in very young seedlings, suggesting that is specifically regulated in certain contexts, although it is almost constitutively controlled.