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 amplified theSulphonamide(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 COL13overexpression (OX) (Fig. 2a) and COL13 RNAi transgenic lines (Fig. 2b) for comparison.
To examine whether COL13 was involved in light responses, the WT, COL13 RNAi, andcol13 seedlings were germinated and grown under different light wavelengths (white, red, blue), as well as under dark conditions. As shown in Fig. S1c, under white or red light, the COL13 RNAi andcol13 seedlings had longer hypocotyls than that of the WT, whereas in blue light or dark conditions, the hypocotyl length of all seedlings was not significantly different. Therefore, our research focused on red light. For further study, COL13 OX, COL13RNAi, col13, and WT seedlings were germinated and grown under red light. We found that the COL13 OX seedlings had shorter hypocotyls than the WT seedlings under red light (Fig. 2c, d). In contrast, the COL13 RNAi and col13 seedlings had longer hypocotyls than the WT seedlings under the same conditions (Fig. 2c, e). These findings suggested that COL13 acts as a positive regulator of red-light-mediated inhibition of hypocotyl elongation.