Fig 6. YUCs-dependent auxin biosynthesis contributes to ethylene enhanced local auxin signaling in root-apex TZ under Al stress.

(A) The expression of DR5rev:GFP, DR5rev:GFP/yuc9, DR5rev:GFP/yuc8 yuc9 and DR5rev:GFP/yucQ transgenes, or of DR5rev:GFP after yucasin treatment, in the epidermis of the root-apex in the presence of Al and/or ACC. Single treatments are performed on five-day old seedlings with 25 μM AlCl₃ for 2 hours or on three-day old seedlings with 1 μM ACC or 10 μM yucasin for 2 hours. Co-treatments were done on three-day old transgenic seedlings (30 seedlings were analysed for each genotype/treatment combination) with pre-treatment with 1 μM ACC or 10 μM yucasin for 2 days, and co-treatment with 1 μM ACC or 10 μM yucasin and 25 μM AlCl₃ for 2 hours. Cell boundaries appear red following propidium iodide staining. The root-apex TZ is marked by white arrowheads. Scale bar: 100μm. (B) Quantification of the Al-induced fluorescence intensity in the TZ of DR5rev:GFP, DR5rev:GFP/yuc9, DR5rev:GFP/yuc8 yuc9 and DR5rev:GFP/yucQ transgenes, or of DR5rev:GFP after yucasin treatment in (A). Around 30 seedlings were measured in each material. The detected fluorescence region in TZ is marked by yellow rectangles. Cell boundaries appear red following propidium iodide staining. Statistical difference from detected fluorescence is indicated by asterisks (Fisher’s exact test, ***P < 0.001).