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Gary Drews

Professor of Biology

 

Research

References

 

 

Research

Our lab studies the angiosperm female gametophyte. The female gametophyte is a seven-celled (eight-nucleate) haploid structure that is essential for angiosperm reproduction. It produces the egg cell and central cell, which, following fertilization, gives rise to the seed's embryo and endosperm, respectively. In addition, the female gametophyte mediates a host of reproductive processes including pollen tube guidance, fertilization, and the induction of seed development.

Our long-term goal is to understand the molecular processes controlling female gametophyte development and function. Currently, understanding these processes is hampered by a paucity of information about the molecules required for female gametophyte development and function. Thus, our initial goal has been to identify these molecules. We are taking three approaches: genetics, enhancer detection, and genomics. For these studies, we are using the model genetic organism Arabidopsis thaliana.

Our main approach, thus far, has been to identify mutations affecting the female gametophyte. In an initial screen of ~2,000 lines, we identified 21 mutants. Phenotypically, these mutants fall into two classes. In the first class, mutant female gametophytes have developmental defects. For example, in the gfa2 mutant, the polar nuclei fail to fuse. In the second class, female gametophyte function is affected. For example, the fem16 mutation affects the initiation of seed development. We, currently, are carrying out a larger screen of ~20,000 lines, from which we expect to identify over 100 new mutants.

Our second approach is enhancer detection. We are screening enhancer-trap lines for expression patterns in specific cells of the female gametophyte. For these studies, we are using the green fluorescent protein (GFP) gene as our reporter gene. We have identified several such lines. For example, Line 49 expresses GFP specifically within the central cell (see Figure).

Our third approach is genomics. The goal of this project is to identify all genes expressed specifically within the mature female gametophyte. Our general approach is to identify mRNAs present in wild-type ovules but missing in the ovules of a mutant lacking a female gametophyte. We are using two methods to identify these mRNAs. First, we are using genomic microarrarys or GeneChips. Second, we are imaging these mRNAs using cDNA-AFLP analysis. Using these methods, we have identified ~800 mRNAs present in wild-type ovules but absent in mutant ovules. We currently are analyzing the expression of these genes throughout the plant. In the near future, we will initiate experiments to mutate all of the genes encoding transcription factors and signal transduction molecules.

 

An enhancer trap line expressing the GFP reporter gene in the central cell of the female gametophyte.

References