A transcriptional hub integrating gibberellin-brassinosteroid signals to promote seed germination in Arabidopsis

Chunmei Zhong, Barunava Patra, Yi Tang, Xukun Li, Ling Yuan, Xiaojing Wang

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Seed germination is regulated by multiple phytohormones, including gibberellins (GAs) and brassinosteroids (BRs); however, the molecular mechanism underlying GA and BR co-induced seed germination is not well elucidated. We demonstrated that BRs induce seed germination through promoting testa and endosperm rupture in Arabidopsis. BRs promote cell elongation, rather than cell division, at the hypocotyl-radicle transition region of the embryonic axis during endosperm rupture. Two key basic helix-loop-helix transcription factors in the BR signaling pathway, HBI1 and BEE2, are involved in the regulation of endosperm rupture. Expression of HBI1 and BEE2 was induced in response to BR and GA treatment. In addition, HBI1- or BEE2-overexpressing Arabidopsis plants are less sensitive to the BR biosynthesis inhibitor, brassinazole, and the GA biosynthesis inhibitor, paclobutrazol. HBI1 and BEE2 promote endosperm rupture and seed germination by directly regulating the GA-Stimulated Arabidopsis 6 (GASA6) gene. Expression of GASA6 was altered in Arabidopsis overexpressing HBI1, BEE2, or SRDX-repressor forms of the two transcription factors. In addition, HBI1 interacts with BEE2 to synergistically activate GASA6 expression. Our findings define a new role for GASA6 in GA and BR signaling and reveal a regulatory module that controls GA and BR co-induced seed germination in Arabidopsis.

Original languageEnglish
Pages (from-to)4708-4720
Number of pages13
JournalJournal of Experimental Botany
Issue number13
StatePublished - Jun 22 2021

Bibliographical note

Publisher Copyright:
© 2021 The Author(s) 2021. Published by Oxford University Press on behalf of the Society for Experimental Biology.


  • Arabidopsis thaliana
  • BEE2
  • GASA6
  • HBI1
  • bHLH
  • brassinosteroids (BRs)
  • gibberellins (GAs)
  • seed germination

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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