CaSPDS , a Spermidine Synthase Gene from Pepper ( Capsicum annuum L.), Plays an Important Role in Response to Cold Stress

Spermidine synthase (SPDS) is a key enzyme in the polyamine anabolic pathway. genes help regulate plant response to environmental stresses, but their roles in pepper remain unclear. In this study, we identified and cloned a SPDS gene from pepper ( L.), named (LOC107847831). Bioinformatics analysis indicated that contains two highly conserved domains: an SPDS tetramerisation domain and a spermine/SPDS domain. Quantitative reverse-transcription polymerase chain reaction results showed that was highly expressed in the stems, flowers, and mature fruits of pepper and was rapidly induced by cold stress. The function of in cold stress response was studied by silencing and overexpressing it in pepper and , respectively. Cold injury was more serious and reactive oxygen species levels were greater in the -silenced seedlings than in the wild-type (WT) seedlings after cold treatment. Compared with the WT plants, the -overexpression plants were more tolerant to cold stress and showed higher antioxidant enzyme activities, spermidine content, and cold-responsive gene ( , , , and ) expression. These results indicate that plays important roles in cold stress response and is valuable in molecular breeding to enhance the cold tolerance of pepper.