Molecular cloning and sequence analysis of the kaurene oxidase (MmKO) gene in mulberry (Morus multicaulis) and patterns of MmKO gene expression under abiotic stress conditions

摘要

A full-length cDNA sequence encoding kaurene oxidase (KO)-a key enzyme in the pathway of gibberellin biosynthesis from mulberry (Morus multicaulis), which we designated MmKO (Patent No. 201510161709.4)-was cloned based on mulberry expressed sequence tags (ESTs) and rapid amplification of cDNA ends (RACE) technology. The full cDNA of MmKO was 1,551 base pairs (bp) in length with an open reading frame (ORF) encoding a protein of 516 amino acids. According to sequence analysis, the protein molecular weight and isoelectric point were predicted to be 58.563 kD and 7.917, respectively, and belonged to the cytochrome p450 superfamily. Phylogenetic analysis based on the amino acid sequences encoded by the KO gene from various species showed that mulberry was closely related to Morus notabilis, Malus domestica, Pyrus bretschneideri, Prunus persica and Fragaria vesca. The expression patterns of the MmKO gene under conditions of drought, salt, ABA and SA stresses were quantified by quantitative real-time reverse transcription-PCR (qRT-PCR). The results showed that the expression level changed significantly under abiotic stress conditions compared to the normal growth environment. Overall, these results showed a better understanding of the molecular basis for the signal transduction mechanism during the stress responses in mulberry trees.