Nana Ankumah’s two objectives have been, first, to characterize heritability and phenotypes of selected mutants, and second, to identify mutations affecting secretory processes that could affect cell wall biosynthesis. For the first, Nana has been working with Chip Hunter using a combination of field genetics and molecular analyses to follow inheritance of putative mutations in key genes for cell wall biosynthesis. The goal is to identify homozygous knockouts for these genes in the Uniform-Mu maize population, and to conduct an initial appraisal of whether the dysfunctional genes lead to detectable phenotypes. Thus far putative knockouts have been identified for CslA7, CslA9, CslD1, CslF4, ExpA10, Expl3, and Gsl9. For the second portion of her project, Nana has designed gene-specific primers for each of the four SCAMP (Secretory Carrier Assisted Membrane Protein) genes in maize, constructed probes, and is using these to screen reverse genetics grids from the UniformMu maize population. She has recently identified her first putative knockout.

Kearston Barnes has been testing the molecular basis for one of the newly-identified shrunken-kernel mutants from the UniformMu maize population. This class of mutants are of particular interest, since previous work identified one of them (the shrunken1 mutant) as arising from a sucrose synthase deficiency that led to impaired cell wall biosynthesis. Here, Kearston and her mentor, Brent O’Brien, determined that the shrunken-1 gene for sucrose synthase is apparently not altered in these plants. In contrast, three other genes in this mutant line were found to carry new Mu inserts (based on bioinformatic analysis of Mu-flanking sequences from Mu-TAIL libraries). Each of these candidate genes is thus being tested for its relationship to the visible mutant phenotype (analysis will show whether offspring homozygous for any of the mutant genes consistently show the mutant phenotype [co-segregate])