Identification and expression analysis of PPO gene family in Nicotiana tabacum

To explore the biological function of polyphenol oxidase (PPO) gene family in tobacco, PPO gene family from Nicotiana tabacum was identified and analyzed. Ten NtPPOs were identified, which were simple in structure. The motif organizations of ten NtPPOs were high conservation. Seven NtPPOs were mapped on the third, fourth, fifth and twentieth chromosomes, and the remaining genes were not located. The genetic relationship of PPOs among Nicotiana tabacum, tomato and potato was close. qRT-PCR results indicated that eight NtPPOs were highly expressed in bud, petal and capsule, contrary to root, stem and leaves. NtPPO7 and NtPPO8 were preferentially expressed in root, which suggested that the functions of NtPPOs diverged in evolution.