KYUDAI NEWS KYUSHU UNIVERSITY CAMPUS MAGAZINE Spring 2014 No.25

13/28

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(receptor, signaling factor, channel etc. )guard cells, but not in guard mother cells. SCAP1 regulates the expression of genes encoding key elements of stomatal functioning and morphogenesis. SCAP1 regulates essential processes of stomatal guard cell maturation and functions as a key transcription factor regulating the nal stages of guard cell differentiation.Stomatal opening is initiated by the activation of H+-ATPases in the guard-cell plasma membrane. In contrast to regulation of H+-ATPase activity, little is known about the translocation of the guard cell H+-ATPase to the plasma membrane. We isolated an Arabidopsis gene PATROL1 that controls the translocation of a major H+-ATPase, AHA1, to the plasma membrane. PATROL1 encodes a protein with a MUN domain, known to mediate synaptic priming in neuronal exocytosis in animals. Environmental stimuli change the localization of plasma membrane-associated PATROL1 protein to an intracellular compartment. Plasma membrane localization of AHA1 and stomatal opening require the association of PATROL1 with AHA1. Increased stomatal opening responses in plants overexpressing PATROL1 enhance the CO2 assimilation rate, promoting plant growth (Fig.4).K+ efux through K+ channels during stomatal closure. Despite their proposed role, no component of the plant membrane anion channel has been identied. We isolated an Arabidopsis mutant slac1 (slow anion channel 1) that is impaired in CO2-dependent leaf temperature change. This study makes a convincing case that SLAC1 is a component of the slow anion efux channel function that controls stomatal pore closure in response to multiple signals.Stomata are highly specialized organs that consist of pairs of guard cells. Although early stages of guard cell differentiation have been described and were interpreted in analogy to processes of cell type differentiation in animals (Fig.3), the downstream development of functional stomatal guard cells remains poorly understood. We 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 identied as a plant-specic Dof-type transcription factor expressed in maturing Professor Koh IbaDepartment of Biology, Faculty of Sciences*3 Negi J, Moriwaki K, Konishi M, Yokoyama R, Nakano T, Kusumi K, Hashimoto-Sugimoto M, Schroeder JI, Nishitani K, Yanagisawa S, Iba K. (2013) A Dof transcription factor, SCAP1, is essential for the development of functional stomata in Arabidopsis. Current Biology 23: 479-484.*4 Hashimoto-Sugimoto M, Higaki T, Yaeno T, Nagami A, Irie M, Fujimi M, Miyamoto M, Akita K, Negi J, Shirasu K, Hasezawa S, Iba K. (2013) A Munc13-like protein in Arabidopsis mediates H+-ATPase translocation that is essential for stomatal responses. Nature Communications 4:2215. doi: 10.1038/ncomms3215.12Kyudai News No.25 Signaling Fig.4 Leaf growth is promoted in PATROL1-over-expressing (OX) plants.Fig.3 Mechanisms of stomatal development.Plants grown under short-day conditions for 7 weeks (A) and further grown under continuous light for 2 weeks (B). Scale bars = 1 cm in A, and 5 cm in B.Three bHLH-type transcription factors (SPCH, MUTE, FAMA) are involved in early stomatal development. A plant-specic transcription factor, SCAP1, directs terminal steps of stomatal development – the functional morphogenesis of kidney-shaped guard cells and the acquisition of specic mechanisms of ion homeostasis including ion channel expression.SCAP1, a Dof transcription factor essential for the development of functional stomata*3A Munc13-like protein, PATROL1, affects stomatal movement and plant biomass via controlling H+-ATPase translocation*4

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