An intragenic suppressor of the Arabidopsis floral organ identity mutant apetala3-1 functions by suppressing defects in splicing.
The Arabidopsis floral organ identity gene APETALA3 (AP3) specifies the identity of petals and stamens in the flower. In flowers mutant for the temperature-sensitive ap3-1 allele, the petals and stamens are partially converted to sepals and carpels, respectively. ap3-1 contains a single nucleotide change in the AP3 gene that alters both an amino acid in the AP3 protein and the 5' splice consensus site for intron 5. Surprisingly, the Ap3-1 mutant phenotype is not due to the missense mutation but instead is due to defects in splicing; specifically, exon 5 is frequently skipped by the splicing machinery at the restrictive temperature. In a screen for suppressors of ap3-1, we isolated an intragenic suppressor, ap3-11, that functions to suppress the splicing defects of ap3-1. Using a reverse transcriptase-polymerase chain reaction assay, we demonstrate that the percentage of full-length exon 5-containing AP3 RNAs correlates with the phenotype of the flowers in both ap3-1 and ap3-11. Rather surprisingly, the ap3-11 suppressor mutation is located in intron 4. One model explaining the function of ap3-11 is that the ap3-11 suppressor creates a novel branch point sequence that causes exon 5 to be more frequently recognized by the splicing machinery. The identification of such a suppressor strongly suggests that exon-scanning models of intron-exon recognition are operative in plants.
Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
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D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D005091:Exons; D005801:Genes, Homeobox; D017343:Genes, Plant; D005816:Genetic Complementation Test; D018398:Homeodomain Proteins / Q000235:genetics; D007438:Introns; D026161:MADS Domain Proteins; D008957:Models, Genetic; D020125:Mutation, Missense; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics; D030821:Plants, Genetically Modified; D012326:RNA Splicing / Q000235:genetics*; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013489:Suppression, Genetic; D013696:Temperature
C101342:APETALA 3 protein, Arabidopsis; D029681:Arabidopsis Proteins; D017931:DNA Primers; D018398:Homeodomain Proteins; D026161:MADS Domain Proteins; D010940:Plant Proteins; D018749:RNA, Plant