CHARACTERIZATION OF 3 MALE-STERILE MUTANTS OF ARABIDOPSIS-THALIANA EXHIBITING ALTERATIONS IN MEIOSIS

Male-sterile mutants are being studied to deepen our understanding of the complex processes of microsporogenesis and microgametogenesis. Due to difficulties associated with isolating the mutated gene, there is currently very little molecular information on the defects responsible for male sterility. As a first step in utilizing male-sterile mutants to better understand the biochemical and molecular processes that con trol pollen development, we have characterized a number of Arabidopsis thaliana lines that were generated by seed transformation and exhibit male sterility. We report here the identification and characterizatio n of three male-sterile A. thaliana lines, all of which are tagged wit h T-DNA and show aberrant meiosis, A detailed cytochemical study was c onducted on these lines to better understand the timing and nature of each mutation and to investigate how these mutations affect subsequent steps of pollen development. All three mutants undergo apparently nor mal morphogenesis until the onset of meiosis. In one line (6492) the m utation is most notable at the tetrad stage when up to eight microspor es can be seen in each-callose-encased tetrad. The resulting mutant mi crospores are of variable sizes and contain different amounts of DNA. Two Other mutants (7219 and 7593) possess many common features, includ ing variable developmental pathways, failure to produce callose, produ ction of vacuolate, coenocytic (multi-nucleate) cells that are surroun ded by persistent microsporocyte walls, and asynchronous patterns of d evelopment. Unlike the situation in wildtype plants, where development al stages are correlated with bud length, such correlations are almost impossible with these two mutants. The sporogenous tissue within all three of these mutant lines collapses prior to anthesis.