NPH3- and PGP-like genes are exclusively expressed in the apical tip region essential for blue-light perception and lateral auxin transport in maize coleoptiles

“Since then, IAA has been shown to be involved in many physiological events (Woodward and Bartel, 2005).”

“At present, there is little information about maize NPH3 and MDR/PGP genes, although it is known that the MDR/PGP gene encoding ABCB1/BR2 has a role in shoot growth, as revealed from analyses of the maize dwarf mutant br2 (Multani et al., 2003; Knöller et al., 2010).”

“These results indicate that other PIN protein(s) or PGP-like transporter(s) are involved in lateral IAA movements, as proposed for Arabidopsis (Noh et al., 2003; Li et al., 2007; Nagashima et al., 2008).”

“In addition, direct binding of AtNPH3 and its homologue AtRPT2 to the phot1 protein was also reported (Motchoulski and Liscum, 1999; Sakamoto and Briggs, 2002; Inada et al., 2004).”

“Among these proteins, AtPIN3 is known to have a role in IAA redistribution in the tropic response of Arabidopsis hypocotyls (Friml and Palme, 2002).”

“These results indicate that other PIN protein(s) or PGP-like transporter(s) are involved in lateral IAA movements, as proposed for Arabidopsis (Noh et al., 2003; Li et al., 2007; Nagashima et al., 2008).”

“In the monocot maize, ZmPIN1a, b, and c are involved in auxin transport during embryogenesis and vegetative development (Carraro et al., 2006; Gallavotti et al., 2008; Forestan et al., 2010).”

“In addition, direct binding of AtNPH3 and its homologue AtRPT2 to the phot1 protein was also reported (Motchoulski and Liscum, 1999; Sakamoto and Briggs, 2002; Inada et al., 2004).”

“In the monocot maize, ZmPIN1a, b, and c are involved in auxin transport during embryogenesis and vegetative development (Carraro et al., 2006; Gallavotti et al., 2008; Forestan et al., 2010).”

“In the monocot maize, ZmPIN1a, b, and c are involved in auxin transport during embryogenesis and vegetative development (Carraro et al., 2006; Gallavotti et al., 2008; Forestan et al., 2010).”

“In addition, it was shown that AtENP/MAB4/NPY1, a NPH3-like protein, functions as a signal transducer during organogenesis and regulates auxin distribution by modifying cellular PIN localization (Cheng et al., 2007; Furutani et al., 2007).”

“Therefore, it is likely that AtNPH3s act downstream of phot1 and regulates the direction of IAA transport by modifying PIN or related protein(s), including MDR1/PGP19 (Blakeslee et al., 2004).”

“CPT1 may act upstream of auxin redistribution induced by unilateral illumination (Haga et al., 2005).”

“At present, there is little information about maize NPH3 and MDR/PGP genes, although it is known that the MDR/PGP gene encoding ABCB1/BR2 has a role in shoot growth, as revealed from analyses of the maize dwarf mutant br2 (Multani et al., 2003; Knöller et al., 2010).”

“In addition, it was shown that AtENP/MAB4/NPY1, a NPH3-like protein, functions as a signal transducer during organogenesis and regulates auxin distribution by modifying cellular PIN localization (Cheng et al., 2007; Furutani et al., 2007).”

“The generally accepted model of phototropism is that the tip region detects the direction of the photo-stimulus, and lateral IAA transport at the tip establishes the asymmetric IAA distribution that moves basipetally, causing the lower region to bend (Briggs et al., 1957; Iino, 1991, 1995; Fuchs et al., 2003).”

“Photos were taken at various times points in each experiment. dcba Vascular system A Thinner side (where leaves emerge) Supplemental Figure 2.”

“In monocot coleoptiles, particularly, IAA is known to be synthesized from Trp at the tip region, and then transported to lower parts (Iino, 1982; Weiler and Wischnewski, 1984; Koshiba et al., 1995; Nishimura et al., 2009).”

“These results are consistent with previous studies, in which the movement of exogenously applied radiolabelled IAA was determined (Pickard and Thimann, 1964; Iino, 1991).”

“The generally accepted model of phototropism is that the tip region detects the direction of the photo-stimulus, and lateral IAA transport at the tip establishes the asymmetric IAA distribution that moves basipetally, causing the lower region to bend (Briggs et al., 1957; Iino, 1991, 1995; Fuchs et al., 2003).”

“1A, the responses were characteristic of the phototropic responses reported previously for maize seedlings (Iino, 1987).”

“It was shown previously that IAA is synthesized from Trp at the very tip region of maize coleoptiles, and the synthesized IAA moves to basal parts via polar transport regulated by ZmPIN1 proteins (Nishimura et al., 2009).”

“However, these investigations were carried out using 5 mm coleoptile sections (Palmer et al., 1993; Hager, 1996; Knieb et al., 2004).”

“In Arabidopsis, it is postulated that AUX1, PIN2, and PIN3 are involved in relocating IAA in response to tropic stimuli (Friml and Palme, 2002; Moore, 2002).”

“The photo-sensing region for 1st pulse-induced positive phototropism was investigated by decapitating maize coleoptiles at various positions (up to 2 mm from the top) immediately after blue light stimulation and applying IAA to cut surfaces (Iino, 1995).”

“This pattern of movement appeared to show effects of gravity, because the phototropic stimulus makes the segments bend away from the vertical axis (Nick and Schäfer, 1988).”

“Moreover, coleoptile tips are known to be the site of IAA production (Iino and Carr, 1982; Koshiba et al., 1995; Bennett et al., 2000; Mori et al., 2005; Nishimura et al., 2009).”

“Phototropic curvature in the maize coleoptile 2 cm segment system In many previous studies on monocot coleoptiles, phototropic curvature in response to various light conditions, including unilateral blue light irradiation, has been studied in ‘whole seedlings’ grown in darkness and/or under red light (Briggs, 1960; Zi…”

“There is evidence that some growth inhibitor(s) increased in the light-irradiated half of oat coleoptiles (Hasegawa and Sakoda, 1988; Togo and Hasegawa, 1991).”

“However, these investigations were carried out using 5 mm coleoptile sections (Palmer et al., 1993; Hager, 1996; Knieb et al., 2004).”

“Decapitation of maize coleoptile is known to make coleoptiles incapable of responding to gravity and light stimuli (Nishimura et al., 2009; Matsuda et al., 2011).”

“NPH3 is expressed predominantly at the coleoptile tip ( Matsuda et al., 2011 ) and has been shown to interact with phot1 both in vitro ( Motchoulski and Liscum, 1999 ) and in vivo ( Lariguet et al., 2006 ).”

“This concept has been proven true to date for coleoptiles of monocotyledonous plants (Holland et al., 2009; Matsuda et al., 2011; Whippo and Hangarter, 2009).”

“Furthermore, Matsuda et al. (2011) found that NPH3-like and PGP-like genes have similar expression patterns in the BL perception organ of maize (Zea mays) coleoptiles, implying a potential cross-link between different signaling pathways via NPH3/NPY1 scaffold proteins.”

“At least one gene, PGP18, has been associated with both light signal perception and cell wall remodeling [35].”

“Nevertheless, they still function in longrange transport of auxin, as the described abcb mutants show defects in their content (Geisler et al. 2005; Geisler & Murphy 2006; Matsuda et al. 2011; Fig.”

“Expression and protein localization of PHOT1 in coleoptile tips perfectly complied with the predicted perception site for phototropism (Knieb et al., 2004; Matsuda et al., 2011).”

“, the sites of signal perception and phototropic bending are distinct [10–12].”

“In addition, PIN1s and PGP (P-glycoprotein)-like genes are expressed in the tip region of the coleoptile (Matsuda et al. 2011).”

“The PGP/ABCB gene family has been mainly studied in Arabidopsis, and briefly in sorghum and maize (Zea mays L.) (Matsuda et al. 2011; Shen et al. 2013).”

“Differences to the wild type were greatly enhanced at apical ends of the stems, correlated with younger, developing tissues (Matsuda et al., 2011) and with higher auxin contents on one hand, and higher ABCB, primarily ABCB1, expression on the other hand [Figure S5 (b)].”

“Although the detailed expression patterns of NPH3 and RPT2 in the hypocotyl are not known yet in Arabidopsis, an NPH3-like gene in maize, which shows high similarity to Arabidopsis NPH3, is exclusively expressed in the top part of the coleoptiles (Matsuda et al. 2011).”

“Additionally, in maize, the NPH3 and PGP genes are specifically expressed at the tip of the maize coleoptile, similar to the expression pattern observed in Arabidopsis (Matsuda et al., 2011).”

“In contrast, it was also observed that MeJA treatment resulted in the up-regulation of auxin transport-related gene ABCB15 (Matsuda et al. 2011) and the IAA-amino acid hydrolase ILR1 (Leclercq et al. 2002) in treated apples (adapted from the original statement).”

“Recent studies revealed that not only the tip but also the lower region of the maize coleoptile may respond to some extent to BL (Matsuda et al. 2011; Suzuki et al. 2014).”

“Screening of 7-B3 using maize coleoptiles Previously, we demonstrated that the maize coleoptile tip is the region of IAA biosynthesis, and that the synthesized IAA is transported into the coleoptile elongation zone, resulting in gravitropic and phototropic responses.(8,28) To screen for new inhibitors of IAA transport…”

“Regulation of IAA biosynthesis and/or transport is controlled by environmental stimuli (Iino 1982; Fuchs et al. 2003; Mori et al. 2005; Nishimura et al. 2006; Matsuda et al. 2011).”

“More recently, we developed a simpler system with 2-cm coleoptile segments detached from maize seedlings to investigate gravi- and phototropic curvatures (Nishimura et al., 2009; Matsuda et al., 2011).”

“…IAA is synthesized in the tip regions of maize coleoptiles (Mori et al. 2005; Nishimura et al. 2014; Sugawara et al. 2015), and that IAA is asymmetrically distributed within maize coleoptiles in response to gravity or blue light (Matsuda et al. 2011; Nishimura et al. 2009; Sugawara et al. 2015).”