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 GA3 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 GA3 but insensitive to paclobutrazol, and their growth correlated to lower concentrations of endogenous GA1 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 GA1, 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.