Sažetak
The MATH-BTB protein family is common to both animals and plants. It is a phenomenon that Arabidopsis and human genomes encode only few members (six and two, respectively) of the MATH-BTB protein family but in some plant and animal organisms, the same protein family has expanded more than 10-fold. The first functionally characterized MATH-BTB protein is Mel26 from Caenorhabditis elegans which is a key regulator required for the first symmetric zygote division. Three different plant MATH-BTB genes, from Zea mays, Triticum aestivum and Arabidopsis thaliana were selected due to their exclusive/strong expression during plant reproduction and functionally characterized in our work. A gametophyte/zygote specific ZmMAB1 gene from maize is expressed in both the female and male germline an d its silencing leads to defects in spindle organization and chromosome segregation during gametophyte development. The zygotic induced gene TaMAB2 encodes a protein that asymmetrically co-localises with microtubuli around the nuclear envelope, what sugges ts its role in organizing the assembly and proper position of microtubular spindles during asymmetric cell divisions of zygote. Moreover, zygote deposited TaMAB2 is always inherited to the large basal cell after first asymmetric zygotic division. The asymmetrically inheritance indicate that the protein might be involved not only into establishment of asymmetry but also into the cell specification in two- celled embryo. ZmMAB1 and TaMAB2 as well as other yeast, animal, and plant BTB-domain containing protein s interact with Cullin 3- based E3 ligases and are involved in ubiquitin- dependent degradation pathway. In addition to Cullin 3-related functions, Arabidopsis MATH -BTB protein AtBPM1, localizes predominantly in nucleolus of plant cells indicating a Cullin3 independent function. We identified, by mass spectrometry and other protein interaction analysis that AtBPM1 interacts with proteins involved in RNA -directed DNA methylation which rep resent a novel, yet undiscovered function of MATH-BTB protein in regulation of DNA methylation.
