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

Abstract

Spermidine synthase (SPDS) is a key enzyme in the polyamine anabolic pathway. <i>SPDS</i> 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 (<i>Capsicum annuum</i> L.), named <i>CaSPDS</i> (LOC107847831). Bioinformatics analysis indicated that <i>CaSPDS</i> contains two highly conserved domains: an SPDS tetramerisation domain and a spermine/SPDS domain. Quantitative reverse-transcription polymerase chain reaction results showed that <i>CaSPDS</i> was highly expressed in the stems, flowers, and mature fruits of pepper and was rapidly induced by cold stress. The function of <i>CaSPDS</i> in cold stress response was studied by silencing and overexpressing it in pepper and <i>Arabidopsis</i>, respectively. Cold injury was more serious and reactive oxygen species levels were greater in the <i>CaSPDS</i>-silenced seedlings than in the wild-type (WT) seedlings after cold treatment. Compared with the WT plants, the <i>CaSPDS</i>-overexpression <i>Arabidopsis</i> plants were more tolerant to cold stress and showed higher antioxidant enzyme activities, spermidine content, and cold-responsive gene (<i>AtCOR15A</i>, <i>AtRD29A</i>, <i>AtCOR47</i>, and <i>AtKIN1</i>) expression. These results indicate that <i>CaSPDS</i> plays important roles in cold stress response and is valuable in molecular breeding to enhance the cold tolerance of pepper.