Gamma-aminobutyric acid (GABA) releases seed dormancy by orchestrating abscisic acid and gibberellin metabolism and signaling

Abstract

Abstract Background Seed dormancy release, regulated by abscisic acid (ABA) and gibberellin (GA), is essential for plant development and yield. Gamma-aminobutyric acid (GABA) is known to mediate plant stress responses; however, its role in seed dormancy release remains elusive. Results Here, we reported that seed dormancy release was impaired in GAD2-deficient seeds lacking GABA biosynthesis while enhanced in GABA-T-deficient seeds with impaired GABA catabolism, indicating a positive regulatory role of GABA in seed dormancy release. Further, ABA antagonized GABA-facilitated seed dormancy release, and GABA failed to alleviate seed dormancy in the GA-deficient mutant ga1-t. Analysis of mutants defective in ABA and GA biosynthesis revealed that seed dormancy release, characterized as decreased ABA content and increased GA3 content, was suppressed in gad2 while enhanced in gaba-t1-1 mutant. Mechanistically, GABA promoted GA3 biosynthesis by upregulating GA20ox1 expression, while inhibited ABA biosynthesis by downregulating NCED6 and upregulating CYP707A2 transcription. GABA also amplified GA signaling and suppressed ABA signaling by downregulating genes expression of DELLAs and ABI3. Further, GABA-mediated seed dormancy alleviation was confirmed in seeds of pear, apple, and cherry, highlighting its broad applicability across diverse plant species. Conclusion Our findings not only advance our understanding on the mechanism of GABA-mediated seed dormancy release via coordinated regulation of abscisic acid and gibberellin pathways, but also highlight the potential of GABA as a natural alternative to synthetic chemicals for promoting sustainable and environmentally friendly agricultural practices.

Keywords

• ABA
• GA
• GABA-T
• GAD
• Gamma-aminobutyric acid
• Seed dormancy