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United States Department of Agriculture

Agricultural Research Service

Research Project: Genomic and Genetic Analysis of the Cereal Circadian System and Crop Production Title: The homeologous Zea mays gigantea genes: characterization of expression and novel mutant alleles

Authors
item Mendoza, Juan-Miguel
item Bendix, Claire -
item Meeley, Robert -
item Harmon, Frank

Submitted to: Maydica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 24, 2013
Publication Date: October 19, 2012
Citation: Mendoza, J.H., Bendix, C., Meeley, R., Harmon, F.G. 2012. The homeologous Zea mays gigantea genes: characterization of expression and novel mutant alleles. Maydica. 57:260-265.

Interpretive Summary: The maize genome has two highly similar copies of the gigantea (gi) gene known as gi1 and gi2. Genes homologous to these in other plant species play critical roles in producing circadian rhythms, as well as regulation of key growth and developmental decisions Here we characterized the expression of these two maize gi genes to better understand their function in maize. Although gi1 and gi2 shared comparable 24-hour rhythmic expression profiles, gi1 levels were consistently higher than gi2. Furthermore, peak gi1 expression was largely unchanged in the length of the photoperiod, while short day photoperiods repressed gi2 expression. The transcriptional unit for gi1 is established based on 5’-RACE analysis. Two independent mutant alleles for gi1 are described that are caused by transposons of the Mutator (Mu) class inserted into the 5’-end of gi1 gene. The type of Mu element and position of the transposon in gi1 was different for each allele. Mutant plants had marked reduction in gi1 expression and carried transcripts interrupted by the Mu element. Together, these results provide a deeper understanding of the gi genes in maize. In addition, the novel gi1 mutant alleles described here will be valuable tools that will enable more comprehensive study gi1 function in maize, as well as the role of circadian clock regulation in maize metabolism, growth, and development.

Technical Abstract: The two homeologous Zea mays gigantea (gi) genes, gi1 and gi2, arose from the last genome duplication event in the maize lineage. Homologs of these genes in other species are required for correct circadian rhythms and proper regulation of growth and development. Here we characterized the expression of these two maize gi genes. Although gi1 and gi2 shared comparable 24-hour rhythmic expression profiles, gi1 levels were consistently higher than gi2. Furthermore, peak gi1 expression was largely unchanged in the length of the photoperiod, while short day photoperiods repressed gi2 expression. The transcriptional unit for gi1 is established based on 5’-RACE analysis. Two independent mutant alleles for gi1 are described that are caused by transposons of the Mutator (Mu) class inserted into the 5’-end of gi1 gene. The type of Mu element and position of the transposon in gi1 was different for each allele. Mutant plants had marked reduction in gi1 expression and carried transcripts interrupted by the Mu element. Together, these results provide a deeper understanding of the gi genes in maize. In addition, the novel gi1 mutant alleles described here will be valuable tools to study gi1 function in maize, as well as the role of circadian clock regulation in maize metabolism, growth, and development.

Last Modified: 10/22/2014
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