Submitted to: Maize Genetics Cooperation Newsletter
Publication Type: Research Notes
Publication Acceptance Date: 3/11/1999
Publication Date: N/A
Citation: Interpretive Summary: Plants produce anthocyanins, which are important components in a plants defense mechanism and provide many of the lovely red and purple colors found in flowers and fruits. In order to manipulate the production of anthocyanins for agricultural purposes, it is important to understand the biochemical processes and the genes responsible for the anthocyanin biochemical pathway. The first biochemical step involves the enzyme chalcone synthase (CHS) which, in maize, is produced by two genes. One of these CHS genes is controlled by a second gene called Intensifier (In). In order to understand how this regulation works a mutation of the In gene (In-D) was analysed using molecular biology techniques. This analysis showed that the In-D mutation is vastly different to the normal gene in many aspects (gene structure and expression) and provides useful insights on how In might regulate CHS production.
Technical Abstract: The C2 and White-pollen (Whp) loci both encode for chalcone synthase (CHS). In the aleurone tissue, the Intensifier locus (In) regulates the production of CHS coming from the Whp locus. Kernels that are in/in allow CHS to be produced from Whp locus, while CHS production from Whp is inhibited in In/(In or in) kernels. In encodes for a myc-related protein, thus indicating In may act as a suppresser of transcription. In order to elicit the regulatory function of In, we began an investigation of In-D. In-D is a semi-dominant mutation of In that inhibits overall production of anthocyanins in the aleurone tissue. Genomic and sequence analysis of In-D uncovered significant differences between the two loci, it appears that In-D consists of two complete, but structurally different, copies of the wild-type allele. Major differences between the duplicated copies in introns 3, 5, 6 and 7 were detected. A large number of cDNAs were isolated from In-D kernels. Sequence analysis of these clones shows, as in the case of In, that In-D exhibits missplicing. The missplicing patterns between the two alleles are very similar except for intron 2. In-D also exhibits premature polyadenlation in intron 2. Northern and Western analysis demonstrate that In-D is expressed at significantly higher levels when compared to In, and that total CHS production is inhibited or delayed.