MOLECULAR AND FUNCTIONAL STUDIES OF EARLY ANTHER DEVELOPMENT IN ARABIDOPSIS

Open Access
- Author:
- Sun, Yujin
- Graduate Program:
- Biology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 10, 2007
- Committee Members:
- Hong Ma, Committee Chair/Co-Chair
Teh Hui Kao, Committee Member
Paula Mc Steen, Committee Member
Naomi S Altman, Committee Member - Keywords:
- SCF complex
Kelch repeat-containing F-box protein
Anther development
Arabidopsis thaliana
Dysfunctional Tapetum1
Solo Dancers - Abstract:
- The Arabidopsis anther is a model system for studying fundamental cellular processes of cell division, cell differentiation, and cell-cell communication. Although a number of genes have been identified to be important for early anther development and meiosis, information on the relationships among these genes is very limited and many more genes important for anther development and/or meiosis are waiting to be discovered. I used several different approaches to study anther development, as described in this thesis. To identify anther preferential genes and to gain insights into the regulatory networks of several known important genes, I worked with two collaborators to perform microarray experiments using mRNA materials extracted from anthers (stages 4-6) of the wild type, the solo dancers (sds) and male meiocyte death1 (mmd1) mutants, as well as mRNA from wild-type young inflorescences (floral stages 1-9). The global gene expression profiles of those tissues were compared. Further studies included gene functional categorization and gene cluster analysis. The information gained from these analyses will contribute to the development of anther gene regulatory networks and guide future experiments to understand anther development. I also performed an evolutionary study of a family of Kelch repeat-containing F-box proteins (KFBs). F-box proteins are major components of SCF complexes and can bind to SKP1 and the protein substrates at the N-terminal F-box motif and the C-terminal protein-protein interaction domain(s), respectively. The KFB family is one of the largest subfamily of F-box proteins and has only been reported for human and Arabidopsis previously. To study the possible evolutionary history of KFBs, I performed extensive BLAST searches to identify putative KFBs in selected organisms, and analyzed their relationships phylogenetically. Gene duplication and gene expression of the KFBs were also investigated in rice and Arabidopsis. This study indicated that the origin of KFBs occurred before the divergence of animals and plants, and that plant KFBs underwent rapid gene duplications. My analyses also suggested that the mechanisms for controlling flower timing and the circadian oscillator might be conserved in flowering plants. In addition, collaborating with a colleague in our laboratory, I performed a functional study of the DYSFUNCTIONAL TAPETETUM1 (DYT1) gene. DYT1 encodes a putative transcription factor and was isolated by map-based cloning using an Arabidopsis male sterile mutant. Phenotypic analysis revealed that DYT1 is required for normal tapetum development and function. The mutant tapetal cells formed excess and/or enlarged vacuoles and lacked the densely stained cytoplasm typical of normal tapetal cells. Although most meiotic processes seemed normal, cytokinesis of meiocytes often failed to occur and meiocytes eventually collapsed within anther locules. Double mutant analysis and gene expression studies also suggested that DYT1 acts downstream of two genes, SPOROCYTELESS/NOZZLE (SPL/NZZ) and EXCESS MICROSPOROCYTES1/EXTRA SPOROGENOUS CELL (EMS1/EXS), which are required for early anther development. The studies also indicated that DYT1 is required for the normal expression of several tapetum genes. These results demonstrated that DYT1 is a crucial component in a genetic network that controls early anther development and function.