Characterization of the rbd1 mutants.

(A) Structure diagram of the RBD1 protein. It contains one RNA recognition motif/ RNA-binding domain between 188–267 amino acid (aa) predicted at SMART (http://smart.embl-heidelberg.de/). (B) Diagram of T-DNA insertion mutants of the RBD1 gene. Arrows indicate the translation start (ATG) and stop (TAA) codons. Triangles indicate the site of T-DNA insertion in the SALK_041100 (rbd1-1) and SALK_012657 (rbd1-2) mutants. ‘a’ and ‘b’ mark the regions for RT-PCR analysis of RBD1 gene expression. (C) Semi-quantitative RT-PCR analysis of RBD1 expression in rbd1 mutants. The Actin gene was used as a normalization control. Bands of each row are cut from the same gel. (D) Phenotype of rbd1 mutants, rbd1 RNAi and complementation lines. Top row: plants grown for 3 weeks at 22°C with 12h light /12h dark. Bottom row: plants grown for 3 weeks at 22°C, then shifted to 4°C for additional 4 weeks with 12h light /12h dark. (E) The rbd1-1 plants at 2 days of 22°C recovery after 3 weeks of 4°C treatment. (F) The accumulation of pigments in rbd1 mutants and complementation lines. Shown are contents of chlorophyll a, chlorophyll b and carotenoid from the fifth and sixth leaves of 2 weeks old plants grown at 22°C with constant light. Means ± SD, n = 3, * represents significant differences between means at P < 0.05 according to Student’s t test.