|Della Vedova, Chris|
Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2005
Publication Date: 8/1/2006
Citation: Della Vedova, C.B., Lorbiecke, R., Kirsch, H., Schulte, M.B., Scheets, K., Borchert, L.M., Scheffler, B.E., Wienand, U., Cone, K.C., Birchler, J.A. 2006. The dominant inhibitory chalcone synthase allele C2-IDF (inhibitor diffuse) from zea mays(L.) acts via an endogenous rna silencing mechanism. Genetics. 170:1989-2002. Interpretive Summary: Anthocyanins are important plant pigments for the plant's health and have nutritional benefits in human diets. The biosynthesis of anthocanins requires many enzymes and the first committed biochemical step is performed by chalcone synthase. In corn this enzyme is encoded by the C2 gene. This manuscript describes a mutation of this gene (C2-Idf) that inhibits production of anthocyanins even in the presence of the normal C2 allele. Therefore, C2-Idf is a rare mutation that acts as a dominant trait and is a repressor of normal function. The C2-Idf was cloned and sequenced. The structure of the alleles is such that it contains three copies of the gene instead of the standard single copy. Experiments indicate the dominant phenotype of C2-Idf is because one of the three copies might be producing a natural anti-sense transcript which would inhibit the production of normal C2 transcripts.
Technical Abstract: C2-Idf is a stable dominant mutation of the chalcone synthase gene c2, a structural gene in the anthocyanin pathway of maize. Homozygous C2-Idf plants show no pigmentation. In heterozygous plants pigmentation and C2 activity are drastically reduced. To explore the nature of this effect, the C2-Idf allele was cloned. The structure of C2-Idf differs substantially from that of the c2 gene. The C2-Idf haplotype represents three copies of the C2 gene. Two copies are located in close proximity to each other in a head to head orientation. In addition, two copies are probably without function due to transposon insertions in either the 5'- or 3'-part of the genes. One copy is almost identical to a functional allele. The structure of C2-Idf suggested that it acts through epigenetic silencing. This hypothesis is consistent with the data described by DELLA VEDOVA et al. in the accompanying paper.