Expression of CCoAOMT from Zingiber officinale Roscoe under NaCl Stress and Its Regulatory Role in 6-Gingerol Biosynthesis

Ginger (Zingiber officinale Roscoe) is of high economic value as a medicinal and food resource. 6‑Gingerol is the predominant bioactive component in the rhizome of ginger. A crucial enzyme involved in 6-gingerol biosynthesis is caffeoyl coenzyme A O-methyltransferase (CCoAOMT). In the present study, the cDNA sequence of ZoCCoAOMT from ginger was cloned. The expression level of ZoCCoAOMT and the contents of 6-gingerol in the rhizome were analyzed in ginger plants treated with different concentrations of NaCl. The full-length ZoCCoAOMT cDNA consisted of 738 bp and showed 96.34% sequence homology with Curcuma longa CCoAOMT. Transcription of ZoCCoAOMT was highly consistent with the trend in accumulation of 6-gingerol. The ZoCCoAOMT transcript level and 6-gingerol content in the rhizome were highest under treatment with 25 g/L NaCl but decreased under higher concentrations of NaCl, which suggested a positive regulatory relationship between ZoCCoAOMT and 6-gingerol synthesis. Virus-induced gene silencing (VIGS) analysis further verified the positive regulatory role of ZoCCoAOMT in 6-gingerol synthesis. The results provide fundamental information for clarification of the role of ZoCCoAOMT in the 6-gingerol biosynthesis pathway of Z. officinale, and also gene resources for 6-gingerol biosynthesis.