October 11, 2019
Important gene called KARAPPO discovered
Many plants reproduce sexually through fertilization, but some reproduce asexually. One form of asexual reproduction is vegetative cloning, in which new individuals independently form from the parent’s roots, stems or leaves. Liverwort (Marchantia polymorpha) propagates by forming asexual buds called gemmae in large numbers in gemma cups on the plant’s surface. Although it was known that gemmae begin to form when the epidermal cells at the bottom of the cup undergo asymmetric division, the molecular mechanism for this process remained completely unknown.
A collaborative research group from Kobe University, Kyoto University, the National Institute for Basic Biology, Kindai University, RIKEN CSRS, Kumamoto University and Temasek Life Sciences Laboratory in Singapore focused on two mutant strains that did not form any gemmae whatsoever. After decoding the entire genome of the mutants with next-generation sequencer analysis, researchers discovered that both strains had the same mutation, which they name KARAPPO (empty in Japanese). Gemmae formed in these mutants when the KARAPPO gene was complemented, indicating that the KARAPPO gene has an essential function in gemmae formation.
Further analysis revealed that the KARAPPO protein is an ROP guanine nucleotide exchange factor (RopGEF), a type of low molecular weight GTPase that controls cell elongation and asymmetric division. Given the above, KARAPPO can be considered to activate ROP to cause asymmetric division of gemma cup epidermis cells and create the cells that become gemmae.
Current Biology doi:10.1016/j.cub.2019.08.071
T. Hiwatashi, H. Goh, Y. Yasui, L. Q. Koh, H. Takami, M. Kajikawa, H. Kirita, T. Kanazawa, N. Minamino, T. Togawa, M. Sato, M. Wakazaki, K. Yamaguchi, S. Shigenobu, H. Fukaki, T. Mimura, K. Toyooka, S. Sawa, K. T. Yamato, T. Ueda, D. Urano, T. Kohchi, K. Ishizaki,
"The RopGEF KARAPPO Is Essential for the Initiation of Vegetative Reproduction in Marchantia polymorpha".
Senior Technical Scientist
Mass Spectrometry and Microscopy Unit