COL13 regulates hypocotyl elongation under red-light conditions
To characterize the role of COL13 in plants, we obtained the corresponding Arabidopsis T-DNA insertion mutant (GK-657F04-023194, termed col13 in the following; Fig.S1a) from GABI-Kat, Max Planck Institute for Plant Breeding Research (Rosso et al., 2003); the mutation was verified by PCR (Fig.S1b), which amplify the sul gene by using the primers listed in Supplementary Table 1. To confirm that the phenotype of the col13 mutant was indeed caused by disruption of the COL13 gene, we generated COL13 overexpression (OX) (Fig.2a) and COL13 RNAi transgenic lines (Fig.2b) for comparison.
To examine whether COL13 is involved in light responses, wild type (WT), COL13 RNAi and col13 seedlings were germinated and grown in different light (White, red, blue), as well as dark condition. As shown in Fig.S1c, under white or red light, the COL13 RNAi and col13seedlings had longer hypocotyls than WT, while in blue light or dark condition, the hypocotyl length of all seedlings were no significant difference. Therefore, our research focus on red light. For further study, COL13 OX, COL13 RNAi, col13 and WT seedlings were germinated and grown in red light. We found that the COL13OX seedlings had shorter hypocotyls than WT in red light (Fig. 2c,d), in contrast, the COL13 RNAi and col13 seedlings had longer hypocotyls than WT under the same conditions (Fig. 2c, e). These findings suggest that COL13 acts as a positive regulator of red light-mediated inhibition of hypocotyl elongation.