Comprehensive expression analysis of ERF transcription factors during chilling acclimation in Saintpaulia

Abstract Saintpaulia (Saintpaulia ionantha), a popular indoor ornamental potted plant, is native to the highlands of Kenya and Tanzania where temperatures rarely fall below 4°C. Chilling injury caused during cultivation and transportation is a major commercial problem in Saintpaulia. In this study, we investigated chilling acclimation in Saintpaulia ‘Kilauea’. Plants grown at 20°C (14 h light/10 h dark) displayed rapid and severe chilling injury after 24-hour exposure to 4°C. However, chilling injury at 4°C could be dramatically reduced by pre-treating the plants at 10°C but not at 6°C. From whole genome analysis, 161 Ethylene-Responsive Factors (ERFs) were identified and classified into 12 clades according to existing reports. Among these ERFs, 43, 8, and 4 ERFs were upregulated at 12, 24, and 48 h after 10°C treatment, respectively. Most of these ERFs had GCC box and/or DRE/CRT core motifs-like sequences in their upstream regions. Finally, we compared the expression of ERFs between the treatments for 24 h at 10°C, an effective temperature for chilling acclimation, and at 6°C, an ineffective temperature. The results showed that the expressions of all six ERFs we investigated were increased by the 10°C treatment, but not or only barely increased by the 6°C treatment. This study suggests that Saintpaulia, a subtropical plant, also has the ability to acclimate to low temperatures and that ERF upregulation is involved in chilling acclimation.