Meeting report: plant genetics and molecular biology

Abstract

The Genetics Society of Korea (GSK) Mini Symposium III was held October 25 2013 at the Mokpo National University, Korea. The topic was Plant Genetics and Molecular Biology. There were two sessions, respectively chaired by Professor Je-Chang Woo (Mokpo National University, Korea), the former GSK president, and Professor ChoongMo Park (Seoul National University, Korea), who will be the next GSK president. In the first session, two speakers presented their findings. The first speaker, professor Sang-Gu Kim (professor emeritus, Seoul National University, Korea), was the founding member and a former president of the GSK and served as the editor-in-chief of the Korean Journal of Genetics (formerly the Genes & Genomics). In his talk, entitled ‘‘Structure–function studies of a plant tyrosyl-DNA phosphodiesterase provide novel insights into DNA repair mechanisms of Arabidopsis thaliana’’, professor Kim briefly introduced the role plant genetics has played in the development of the GSK, since the founding of the society and then discussed his previous research and findings. Tyrosyl-DNA phosphodiesterase 1 (TDP1) is a member of the phospholipase D superfamily. It catalyzes the hydrolysis of a phosphodiester bond between a tyrosine residue and the 30-phosphate of DNA. Professor Kim’s group isolated TDP1 from Arabidopsis thaliana (AtTDP), which is an ortholog of yeast and human TDP. AtTDP hydrolyzes the 30-phosphotyrosyl DNA substrate, which is related to repairing DNA damage induced by topoisomerase I in vivo. An analysis of the substrate-saturation kinetics of the full-length AtTDP versus those of a truncated AtTDP mutant lacking the N-terminal SMAD/forkhead-associated domain showed that the kinetic parameters of recombinant AtTDP protein and the AtTDP 1-122 (TDP domain) are equivalent to those of the full-length AtTDP. The loss-offunction AtTDP displayed developmental defects and a dwarf phenotype, which was caused by decreased cell numbers rather than changes in cell sizes. The mutant tdp plants exhibited hypersensitivity to camptothecin, a potent topoisomerase I inhibitor, and rigorous cell death in their cotyledons and rosette leaves, suggesting a failure of DNA damage repair. This was the first clear evidence in plants that AtTDP plays a role in DNA repair. The second speaker in the first session was professor Jeong-Il Kim (Chonnam National University, Korea). The title of professor Kim’s talk was ‘‘Development of hyperactive phytochromes from the structure–function study in plant light signaling’’. Phytochromes are photoreceptors that regulate various aspects of plant growth and development in response to red/far-red light signals from the environment. Red-light absorbing (Pr) phytochromes (kmax = 660 nm) are biosynthesized in the dark. Pr phytochromes can be phototransformed into biologically active, far-red light-absorbing (Pfr) phytochromes (kmax = 680 nm) upon exposure to red light. This photoactivation induces a highly regulated signaling network for photoresponses in plants, which may be one of most the important biochemical reactions on Earth, because we all depend on the light-harvesting machinery of plants. Seeking biotechnological applications for crop improvement, professor Kim’s group used Arabidopsis to generate hyperactive phytochrome mutants, including J.-K. Oh J.-C. Woo Department of Biology, Mokpo National University, Mokpo, Korea