A putative 2OG-Fe(II) oxygenase’s response to gibberellin deficiency is related to the internodal growth of columnar apples

Columnar apples are a labor saving and productive tree form that has long been of interest to apple breeders and producers. MdCo31 , which encodes a putative 2OG-Fe(II) oxygenase, is a potential candidate gene involved in controlling the internode length of columnar growth of apple. In this study, a putative regulation in internode length was conducted by exogenous application of GA 3 and paclobutrazol. The results showed that the MdCo31 -GFP fusion protein was specifically localized in the cytoplasm. Heterologous over-expression of MdCo31 in tobacco produced stunted phenotypes with high chlorophyll content in leaves, and delayed the timing of seed germination and flowering. The over-expression tobacco plants were more sensitive to exogenous application of GA 3 but insensitive to paclobutrazol, and their growth correlated to lower concentrations of endogenous GA 1 and lower expression levels of the gibberellin-regulated family gene NtGASA6 . The higher the MdCo31 expression levels were identified in more dwarf transformants with the shorter internodes. This research proposed that the decrease in endogenous GA 1 , resulting from high MdCo31 expression, induced dwarf phenotypes and shorted internodes, which indicated that MdCo31 is responded to gibberellins’ deficiency conferring the internodal growth of columnar apples.