Fig. 8

The expression profiles of IbAP2/ERF genes in the roots at different developmental stages (a) and during storage process at low temperature (b) analyzed by qRT-PCR. Fibrous roots (S1, root diameter of 2 mm), pencil roots (S2, root diameter of 5 mm) and storage roots at two stages (S3 and S4; root diameters of 15 mm and 25 mm respectively) from the sweet potato plants were harvested at six months after planting. Then, the collected storage roots were stored at 4 °C. Tuberous roots were collected at 0 (control), 2, and 6 weeks after low temperature treatment. The expression data were normalized to 1 in S1 and unstressed plants (0 w). Bars represent the mean of replicates ± standard error. * and ** indicate a significant difference at P < 0.05 and < 0.01, respectively, determined by Student’s t-test