Fig. 1.

(A) Comparison of the genomic sequences of wild-type Arabidopsis thaliana arc6 (WT; gene At5g42480), arc6-1, and arc6-4. A single point mutation at nucleotide (nt) 1141 (C to T) is present in arc6-1, while arc6-4 has a single point mutation at nt 1162 (G to A) which is the first base in the donor site for the third intron. A putative splice site at nt 1169–1170 (GT) may lead to alternative splicing. The use of upper- and lower-case lettering for the nucleotides denotes exon and intron regions, respectively. (B) Gene structure. Exons are depicted as black rectangles; ATG and TAA are the translation initiation and termination codons, respectively. The point mutation in arc6-4 probably prevents excision of the intron and allows for its translation, which if the alternative splice site is not recognized, will lead to a truncated protein product due to a stop codon (TAA) at nt 1186–1188.