The arginine decarboxylase gene CsADC1, associated with the polyamine pathway, plays an important role in tea cold tolerance

Arginine decarboxylase (ADC) is an important enzyme responsible for polyamine (PA) synthesis in plants. In our study, 5 tea varieties were used to investigate the relationship between ADC and cold tolerance in field experiments. A strong and positive correlation was found between cold stress-regulated expression levels of CsADC1 and arginine (Arg) content (R2 > 0.75) in tea mesophyll cells and cold tolerance in 5 tea varieties. An exogenous supply of Arg significantly enhanced cold tolerance. To further clarify the location of CsADC1, the full-length cDNA of the CsADC1 gene was cloned and located in the cell nucleus. Moreover, cold stress significantly promoted the production of MDA in CsADC1-silenced leaves compared with WT plants, which exhibited poor cold tolerance. In contrast, under cold conditions, higher Fv/Fm and lower MDA were detected in CsADC1-overexpressing Arabidopsis than in the WT plants. Furthermore, CsADC1-silenced leaves inhibited the expression levels of the PA metabolism genes CsAIH, CsCPA, CsSPDS, CsSPMS1 and CsSPMS2 under cold stress; thus, significantly lower (p < 0.05) putrescine (Put), spermidine (Spd) and spermine (Spm) content was d etected in CsADC1-silenced tea leaves under cold stress. Taken together, our results indicated that CsADC1, as a positive regulator, played an important role in cold tolerance, which may be due to modulation of polyamine pathways in the cold stress response.