|Porch, Timothy - Tim|
Submitted to: Maize Genetics Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/2004
Publication Date: 3/11/2004
Citation: Tseung, C., Porch, T.G., McCarty, D.R., Settles, M. 2004. Biochemical and molecular characterization of maize vp13 mutants [abstract]. Maize Genetics Conference Abstracts. Interpretive Summary:
Technical Abstract: Abscisic Acid (ABA) is necessary for seed maturation and dormancy, and ABA deficiency in maize often results in viviparous seed. Three viviparous loci have been cloned and two are required for ABA biosynthesis (vp14 and vp5), while one is crucial in ABA signaling (vp1). The viviparous13 (vp13) mutant presents a novel phenotype characterized by normal accumulation of carotenoids and a distinctive lethal phenotype at the seedling stage. Five vp13 alleles have been isolated from a number of Mutator populations and introgressed into W22. We cloned the vp13 locus using MuTAIL-PCR to amplify transposon flanking sequences from both mutant and normal siblings. A vp13 specific transposon flanking sequence was used to identify a BAC containing the Vp13 locus. The sequence of this locus shows homology to Cnx1 genes that are involved in molybdenum cofactor (Moco) biosynthesis. We have identified molecular lesions in three of the five vp13 alleles indicating that the maize Cnx1 homologue is the Vp13 gene. Moco is required for the final aldehyde oxidase step of ABA biosynthesis in addition to other enzymes. Consistent with the predicted function of Cnx1 in maize, we show that vp13 mutants lack aldehyde oxidase, xanthine dehydrogenase, and sulfite oxidase activities. In addition endogenous ABA levels of vp13 mutant seedlings are reduced, and vp13 seedling growth is sensitive to exogenous ABA. These data suggest that vp13 is a pleiotropic biosynthetic mutant and suggest that there is an essential function of one or more Moco requiring enzymes in plants.