Fig. 2.

Transcript levels of genes encoding enzymes of GA biosynthesis in noncolonized (−AMF) della1/della2 and wild-type roots and in della1/della2 and wild-type roots colonized with G. versiforme (+AMF) at 21 d.p.i. as assayed by quantitative RT-PCR. GAs are synthesized from geranylgeranyl diphosphate (GGDD) (116). (A and B) ent-kaurene synthase is involved in the conversion of GGDD to ent-kaurene, which is further converted to ent-kaurenoic acid, catalyzed by ent-kaurene oxidase. Ent-kaurenoic acid is subsequently converted to GA₁₂. (C) GA 20-oxidases (GA20ox) catalyze the sequential oxidation of C-20 to convert GA₁₂ to bioactive GAs. (D) GA 2-oxidases (GA2ox) catalyze GA inactivation reactions. Data are averages ± SEM (n ≥ 6, where N denotes the number of independent roots samples). **P ≤ 0.01.