Figure 5. Antagonism of GA on ABA signalling by GA-promoted degradation of SnRK2s.

(a) Treatment for 3 h with 100 μM GA₃ reduces, while treatment with 10 μM ABA increases the levels of SAPK10, SAPK8 and SAPK9 proteins in OE17 plants. Left panel shows a representative western blot. Right panel shows the SAPKs/HSP82 relative protein level corresponding to left panel. Values are means±s.d. (n=3 replicates). Student's t-test analysis indicated a significant difference (compared with corresponding control (CK), *P<0.05, **P<0.01). Note: The seeds or seedlings were pre-treated for 1 h with 1 mM cycloheximide before phytohormone treatment. (b and c) Western blot analysis showing the levels of SAPK10, SAPK8, SAPK9 and R10 proteins in WT Taichung 65 (T65) and its GA-insensitive dwarf1 mutant (gid1) (b) or in WT Nipponbare (Nip) and its GA biosynthesis mutant dwarf 18 (d18) (c). (d) A model shows that the SnRK2-APC/C^TE regulatory module underlies the antagonism between GA and ABA. Dashed arrows or bars represent indirect action and solid arrows or bars represent direct action. The ‘α-HSP82' signals in a–c show that roughly equal amounts of total plant extracts were used.