The apple gene responsible for columnar tree shape reduces the abundance of biologically active gibberellin

Authors

Watanabe, Daichi; Takahashi, Ikuo; Jaroensanti-Takana, Naiyanate; Miyazaki, Sho; Jiang, Kai; Nakayasu, Masaru; Wada, Masato; Asami, Tadao; Mizutani, Masaharu; Okada, Kazuma; Nakajima, Masatoshi*

Abstract

Ectopic expression of the apple 2‐oxoglutarate‐dependent dioxygenase (DOX, 2ODD) gene, designated MdDOX‐Co, is thought to cause the columnar shape of apple trees. However, the mechanism underlying the formation of such a unique tree shape remains unclear. To solve this problem, we demonstrated that Arabidopsis thaliana overexpressing MdDOX‐Co contained reduced levels of biologically active gibberellin (GA) compared to wild type. In summary, (i) with biochemical approaches, the gene product MdDOX‐Co was shown to metabolize active gibberellin A₄ (GA₄) to GA₅₈ (12‐OH‐GA₄) in vitro. MdDOX‐Co also metabolized its precursors GA₁₂ and GA₉ to GA₁₁₁ (12‐OH‐GA₁₂) and GA₇₀ (12‐OH‐GA₉), respectively. (ii) Of the three 12‐OH‐GAs, GA₅₈ was still active physiologically, but not GA₇₀ or GA₁₁₁. (iii) Arabidopsis MdDOX‐Co OE transformants converted exogenously applied deuterium‐labeled (d₂)‐GA₁₂ to d₂‐GA₁₁₁ but not to d₂‐GA₅₈, whereas transformants converted applied d₂‐GA₉ to d₂‐GA₅₈. (iv) GA₁₁₁ is converted poorly to GA₇₀ by GA 20‐oxidases in vitro when GA₁₂ is efficiently metabolized to GA₉. (v) No GA₅₈ was detected endogenously in MdDOX‐Co OE transformants. Overall, we conclude that 12‐hydroxylation of GA₁₂ by MdDOX‐Co prevents the biosynthesis of biologically active GAs in planta, resulting in columnar phenotypes.

Paper Information

Journal: : The Plant Journal
DOI: : 10.1111/tpj.15084; : https://onlinelibrary.wiley.com/doi/abs/10.1111/tpj.15084