Endogenous H 2 S promotes Arabidopsis flowering through the regulation of GA20ox4 in the gibberellin pathway

Abstract Flowering time is a critical determinant of plant reproductive success and agricultural yield. Hydrogen sulfide (H₂S), as a signaling molecule, regulates various aspects of plant growth and development. In this study, we examined the role of endogenous H₂S in regulating flowering time in Arabidopsis . The O ‐ acetylserine thiol lyase a1 ( oasa1 ) mutant, which has elevated H₂S levels due to impaired OASA1 activity that catalyzes the synthesis of Cys from H 2 S, flowers earlier than wild type (WT). The OASA1 overexpression lines ( OE‐OASA1‐#33/#142 ), characterized by reduced H₂S levels, show delayed flowering, accompanied by decreased expression of key flowering regulators, FLOWERING LOCUS T ( FT ), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 ( SOC1 ), and AGAMOUS‐LIKE24 ( AGL24 ). Notably, vernalization and short‐day (SD) conditions did not affect their flowering patterns. Exogenous H₂S and GA₃ treatment rescued the delayed flowering phenotype of OE‐OASA1‐#33/#142 . In oasa1 , levels of GA intermediates (GA 15 and GA 53 ) were elevated, while their levels were reduced in OE‐OASA1‐#33/#142 . RT‐qPCR analysis showed a significant reduction in the expression of GIBBERELLIN 20‐OXIDASE 4 ( GA20ox4 ) in OE‐OASA1‐#33/#142 compared to WT. Overexpression of GA20ox4 ( OE‐GA20ox4‐#20/#30 ) resulted in earlier flowering and partially rescued the delayed flowering phenotype of OE‐OASA1‐#33/#142 . Additionally, the expression of age pathway‐related genes, including miRNA172b and SQUAMOSA PROMOTER BINDING PROTEIN‐LIKE 3/4/5/9/15 ( SPL3/4/5/9/15 ), was significantly reduced in OE‐OASA1‐#33/#142 seedlings. These findings suggest that endogenous H₂S positively regulates GA20ox4 expression, thereby promoting gibberellin synthesis and advancing flowering in Arabidopsis through the GA pathway. Furthermore, the promotion of flowering by H₂S appears to be linked to the age pathway.