Design, Synthesis, and Biological Activity of 16,17-Dihydro Gibberellin A5 Derivatives as Novel Plant Growth Regulators

Designing 16,17-dihydro gibberellin A5-13-acetate (DHGA₅) derivatives based on GA3β-hydroxylase (GA3ox) structural features represents an ideal strategy for developing novel plant growth retardants. Building upon our previous findings, we designed and synthesized a series of carboxyl-protected DHGA₅ derivatives bearing thiosemicarbazone and 1,3,4-thiadiazole moieties. Following photolytic deprotection, compounds 10e and 11l emerged as the most active compounds in their respective series. Notably, compound 10e exhibited superior activity (IC₅₀ = 90 μM) compared to DHGA₅ (IC₅₀ = 97 μM) in Arabidopsis root growth inhibition and exhibited enhanced activity in suppressing the elongation of rice second leaf sheath. The computational simulation results indicated that deprotected compound 10e enhanced binding to OsGA3ox2 through interactions with additional amino acid residues. Interestingly, derivatives showed unexpected potential in alleviating oxidative damage caused by salt stress. This study presents a promising strategy for the development of novel gibberellin biosynthesis inhibitors as potential plant growth retardants.

16,17-dihydro gibberellin A5; GA3β-hydroxylase; inhibitor; plant growth retardant.