TY - JOUR A1 - Taniguchi, Masatoshi A1 - Furutani, Masahiko A1 - Nishimura, Takeshi A1 - Nakamura, Moritaka A1 - Fushita, Toyohito A1 - Iijima, Kohta A1 - Baba, Kenichiro A1 - Tanaka, Hirokazu A1 - Toyota, Masatsugu A1 - Tasaka, Masao A1 - Morita, Miyo Terao T1 - The Arabidopsis LAZY1 Family Plays a Key Role in Gravity Signaling within Statocytes and in Branch Angle Control of Roots and Shoots JF - The plant cell N2 - During gravitropism, the directional signal of gravity is perceived by gravity-sensing cells called statocytes, leading to asymmetric distribution of auxin in the responding organs. To identify the genes involved in gravity signaling in statocytes, we performed transcriptome analyses of statocyte-deficient Arabidopsis thaliana mutants and found two candidates from the LAZY1 family, AtLAZY1/LAZY1-LIKE1 (LZY1) and AtDRO3/AtNGR1/LZY2. We showed that LZY1, LZY2, and a paralog AtDRO1/AtNGR2/LZY3 are redundantly involved in gravitropism of the inflorescence stem, hypocotyl, and root. Mutations of LZY genes affected early processes in gravity signal transduction without affecting amyloplast sedimentation. Statocyte-specific expression of LZY genes rescued the mutant phenotype, suggesting that LZY genes mediate gravity signaling in statocytes downstream of amyloplast displacement, leading to the generation of asymmetric auxin distribution in gravity-responding organs. We also found that lzy mutations reversed the growth angle of lateral branches and roots. Moreover, expression of the conserved C-terminal region of LZY proteins also reversed the growth direction of primary roots in the lzy mutant background. In lateral root tips of lzy multiple mutants, asymmetric distribution of PIN3 and auxin response were reversed, suggesting that LZY genes regulate the direction of polar auxin transport in response to gravity through the control of asymmetric PIN3 expression in the root cap columella. Y1 - 2017 U6 - https://doi.org/10.1105/tpc.16.00575 SN - 1040-4651 SN - 1532-298X VL - 29 SP - 1984 EP - 1999 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Nakamura, Moritaka A1 - Claes, Andrea R. A1 - Grebe, Tobias A1 - Hermkes, Rebecca A1 - Viotti, Corrado A1 - Ikeda, Yoshihisa A1 - Grebe, Markus T1 - Auxin and ROP GTPase Signaling of Polar Nuclear Migration in Root Epidermal Hair Cells JF - Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants N2 - Polar nuclear migration is crucial during the development of diverse eukaryotes. In plants, root hair growth requires polar nuclear migration into the outgrowing hair. However, knowledge about the dynamics and the regulatory mechanisms underlying nuclear movements in root epidermal cells remains limited. Here, we show that both auxin and Rho-of-Plant (ROP) signaling modulate polar nuclear position at the inner epidermal plasma membrane domain oriented to the cortical cells during cell elongation as well as subsequent polar nuclear movement to the outer domain into the emerging hair bulge in Arabidopsis (Arabidopsis thaliana). Auxin signaling via the nuclear AUXIN RESPONSE FACTOR7 (ARF7)/ARF19 and INDOLE ACETIC ACID7 pathway ensures correct nuclear placement toward the inner membrane domain. Moreover, precise inner nuclear placement relies on SPIKE1 Rho-GEF, SUPERCENTIPEDE1 Rho-GDI, and ACTIN7 (ACT7) function and to a lesser extent on VTI11 vacuolar SNARE activity. Strikingly, the directionality and/or velocity of outer polar nuclear migration into the hair outgrowth along actin strands also are ACT7 dependent, auxin sensitive, and regulated by ROP signaling. Thus, our findings provide a founding framework revealing auxin and ROP signaling of inner polar nuclear position with some contribution by vacuolar morphology and of actin-dependent outer polar nuclear migration in root epidermal hair cells. Y1 - 2017 U6 - https://doi.org/10.1104/pp.17.00713 SN - 0032-0889 SN - 1532-2548 VL - 176 IS - 1 SP - 378 EP - 391 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Mao, Hailiang A1 - Nakamura, Moritaka A1 - Viotti, Corrado A1 - Grebe, Markus T1 - A Framework for Lateral Membrane Trafficking and Polar Tethering of the PEN3 ATP-Binding Cassette Transporter JF - Plant physiology : an international journal devoted to physiology, biochemistry, cellular and molecular biology, biophysics and environmental biology of plants N2 - The outermost cell layer of plants, the epidermis, and its outer (lateral) membrane domain facing the environment are continuously challenged by biotic and abiotic stresses. Therefore, the epidermis and the outer membrane domain provide important selective and protective barriers. However, only a small number of specifically outer membrane-localized proteins are known. Similarly, molecular mechanisms underlying the trafficking and the polar placement of outer membrane domain proteins require further exploration. Here, we demonstrate that ACTIN7 (ACT7) mediates trafficking of the PENETRATION3 (PEN3) outer membrane protein from the trans-Golgi network (TGN) to the plasma membrane in the root epidermis of Arabidopsis (Arabidopsis thaliana) and that actin function contributes to PEN3 endocytic recycling. In contrast to such generic ACT7-dependent trafficking from the TGN, the EXOCYST84b (EXO84b) tethering factor mediates PEN3 outer-membrane polarity. Moreover, precise EXO84b placement at the outer membrane domain itself requires ACT7 function. Hence, our results uncover spatially and mechanistically distinct requirements for ACT7 function during outer lateral membrane cargo trafficking and polarity establishment. They further identify an exocyst tethering complex mediator of outer lateral membrane cargo polarity. Y1 - 2016 U6 - https://doi.org/10.1104/pp.16.01252 SN - 0032-0889 SN - 1532-2548 VL - 172 SP - 2245 EP - 2260 PB - American Society of Plant Physiologists CY - Rockville ER -