Figure 1.

Schematic Diagram of GA Metabolism and Response Pathways.

Conversion of GA₁₂ and GA₅₃ to GA₁₁₀ and GA₉₇, respectively, by 2β-hydroxylation was demonstrated experimentally only for GA2ox6 in this study. GA2ox5, GA2ox6, and GA2ox9 are proposed to have similar functions due to the presence of three conserved motifs unique to C₂₀ GA2oxs. Inactivation of C₁₉-GA precursors, GA₁ and GA₄ by the C₁₉ GA2oxs, GA2ox1 and GA2ox3, in rice was demonstrated experimentally (Sakamoto et al., 2001; Sakai et al., 2003). Bioactive GA positively regulates germination, stem and root elongation, and flower development but negatively regulates OSH1 and TB1 that control tillering. GA also negatively regulates adventitious root development.