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Juntaro Negi Last modified date:2018.06.22

Associate Professor / Informational biology
Department of Biology
Faculty of Sciences


Graduate School
Undergraduate School


E-Mail
Academic Degree
Ph.D
Country of degree conferring institution (Overseas)
No
Field of Specialization
plant physiology
Total Priod of education and research career in the foreign country
00years00months
Research
Research Interests
  • New insight into the function of the guard cell chloroplast by a genetic approach
    keyword : guard cell chloroplast
    2013.03~2014.10.
  • The development of functional stomata in Arabidopsis
    keyword : Dof transcription factor, SCAP1
    2008.05~2013.02.
  • Molecular mechanism of guard cell CO2 sensing
    keyword : CO2 stomata mutant SLAC1
    2002.04.
Academic Activities
Reports
1. Juntaro Negi, Mimi Hashimoto-Sugimoto, kensuke kusumi, Koh Iba, New Approaches to the Biology of Stomatal Guard Cells, Plant Cell Physiol., 2014.02, [URL], CO2 acts as an environmental signal that regulates stomatal movements. High CO2 concentrations reduce stomatal aperture, whereas low concentrations trigger stomatal opening. In contrast to our advanced understanding of light and drought stress responses in guard cells, the molecular mechanisms underlying stomatal CO2 sensing and signaling are largely unknown. Leaf temperature provides a convenient indicator of transpiration, and can be used to detect mutants with altered stomatal control. To identify genes that function in CO2 responses in guard cells, CO2-insensitive mutants were isolated through high-throughput leaf thermal imaging. The isolated mutants are categorized into three groups according to their phenotypes: (i) impaired in stomatal opening under low CO2 concentrations; (ii) impaired in stomatal closing under high CO2 concentrations; and (iii) impaired in stomatal development. Characterization of these mutants has begun to yield insights into the mechanisms of stomatal CO2 responses. In this review, we summarize the current status of the field and discuss future prospects. .
Papers
1. Juntaro Negi, Kosuke Moriwaki, Mineko Konishi, Ryusuke Yokoyama, Toshiaki Nakano, kensuke kusumi, Mimi Hashimoto-Sugimoto, Julian I. Schroeder, Kazuhiko Nishitani, Shuichi Yanagisawa, Koh Iba, A Dof Transcription Factor, SCAP1, Is Essential for the Development of Functional Stomata in Arabidopsis., Current Biology, 23, 6, 479-484, 2013.03, Stomata are highly specialized organs that consist of pairs of guard cells and regulate gas and water vapor exchange in plants. Although early stages of guard cell differentiation have been described and were interpreted in analogy to processes of cell type differentiation in animals, the downstream development of functional stomatal guard cells remains poorly understood. We have isolated an Arabidopsis mutant, stomatal carpenter 1 (scap1), that develops irregularly shaped guard cells and lacks the ability to control stomatal aperture, including CO2-induced stomatal closing and light-induced stomatal opening. SCAP1 was identified as a plant-specific Dof-type transcription factor expressed in maturing guard cells, but not in guard mother cells. SCAP1 regulates the expression of genes encoding key elements of stomatal functioning and morphogenesis, such as K+ channel protein, MYB60 transcription factor, and pectin methylesterase. Consequently, ion homeostasis was disturbed in scap1 guard cells, and esterification of extracellular pectins was impaired so that the cell walls lining the pores did not mature normally. We conclude that SCAP1 regulates essential processes of stomatal guard cell maturation and functions as a key transcription factor regulating the final stages of guard cell differentiation..
2. Juntaro Negi, Osamu Matsuda, Takashi Nagasawa, Yasuhiro Oba, Hideyuki Takahashi, Maki Kawai-Yamada, Hirofumi Uchimiya, Mimi Hashimoto, Koh Iba, CO2 regulator SLAC1 and its homologues are essential for anion homeostasis in plant cells, Nature, 452, 27, 483-486, 2008.03, The continuing rise in atmospheric [CO2] is predicted to have diverse and dramatic effects on the productivity of agriculture, plant ecosystems and gas exchange. Stomatal pores in the epidermis provide gates for the exchange of CO2 and water between plants and the atmosphere, processes vital to plant life. Increased [CO2] has been shown to enhance anion channel activity proposed to mediate efflux of osmoregulatory anions (Cl- and malate(2-)) from guard cells during stomatal closure. However, the genes encoding anion efflux channels in plant plasma membranes remain unknown. Here we report the isolation of an Arabidopsis gene, SLAC1 (SLOW ANION CHANNEL-ASSOCIATED 1, At1g12480), which mediates CO2 sensitivity in regulation of plant gas exchange. The SLAC1 protein is a distant homologue of bacterial and fungal C4-dicarboxylate transporters, and is localized specifically to the plasma membrane of guard cells. It belongs to a protein family that in Arabidopsis consists of four structurally related members that are common in their plasma membrane localization, but show distinct tissue-specific expression patterns. The loss-of-function mutation in SLAC1 was accompanied by an over-accumulation of the osmoregulatory anions in guard cell protoplasts. Guard-cell-specific expression of SLAC1 or its family members resulted in restoration of the wild-type stomatal responses, including CO2 sensitivity, and also in the dissipation of the over-accumulated anions. These results suggest that SLAC1-family proteins have an evolutionarily conserved function that is required for the maintenance of organic/inorganic anion homeostasis on the cellular level..
Presentations
1. Juntaro Negi, Kosuke Moriwaki, Mineko Konishi, Ryusuke Yokoyama, Toshiaki Nakano, kensuke kusumi, Mimi Hashimoto-Sugimoto, Julian I. Schroeder, Kazuhiko Nishitani, Shuichi Yanagisawa, Koh Iba, SCAP1, a master regulator of the development of functional stomata in Arabidopsis, International Workshop on Plant Membrane Biology (IWPMB2013) , 2013.03, Stomata are highly specialized organs which consist of pairs of guard cells and
regulate gas and water vapor exchange in plants. While early stages of guard
cell differentiation have been described and were interpreted in analogy to
processes of cell type differentiation in animals, the downstream development
of functional stomatal guard cells remains poorly understood. We have isolated
an Arabidopsis mutant, scap1 (stomatal carpenter 1), that develops irregularly
shaped guard cells and lacks the ability to control stomatal aperture, including
CO2-induced stomatal closing and light-induced stomatal opening. SCAP1 was
identified as a plant-specific Dof-type transcription factor expressed in maturing
guard cells but not in guard mother cells. SCAP1 regulates the expression
of genes encoding key elements of stomatal functioning and morphogenesis,
such as a K+ channel, MYB60 transcription factor, and pectin methyl esterase.
Consequently, ion homeostasis was disturbed in scap1 guard cells, and
esterification of extracellular pectins was impaired so that the cell walls lining
the pores did not mature normally. We conclude that SCAP1 regulates essential
processes of stomatal guard cell maturation and function as a master regulator
of the final stages of guard cell differentiation.
.
Membership in Academic Society
  • The Botanical Society of Japan
  • The Japanese Society of Plant Physiologsts
  • Japanese Society for Plant Cell and Molecular Biology
Awards
  • New insight into the mechanisms of stomatal regulation and morphogenesis