Weisiensin B inhibits primary and lateral root development by interfering with polar auxin transport in Arabidopsis thaliana

Weisiensin B, a new ent-kaurene diterpenoid isolated from Isodon weisiensis (C. Y. Wu) H. Hara, exhibited phytotoxic effects on root growth and lateral root development in Arabidopsis thaliana seedlings. Primary root growth and lateral root formation in A. thaliana seedlings were significantly inhibited by 10-20 μM weisiensin B. Additionally, the role of weisiensin B in response to polar auxin transport in A. thaliana roots was investigated using a PIN promoter (PIN::GUS), a green fluorescent protein (GFP) fusion protein reporter (PINs::PINs:GFP), and DR5::GUS and DR5::GFP reporter genes. The results indicated that weisiensin B reduced the expression of PIN2, PIN3, PIN4, PIN7, and AUX1 genes and significantly decreased the abundance of PIN2-GFP, PIN3-GFP, PIN4-GFP, PIN7-GFP, and AUX1-GFP fusion proteins at their respective cellular locations, simultaneously causing auxin accumulation in the root apex. These results suggest that weisiensin B interferes with polar auxin transport in A. thaliana roots, resulting in auxin accumulation in the root meristematic cells and the inhibition of root growth and lateral root development.