Phytochromes and cryptochromes regulate the differential growth of Arabidopsis hypocotyls in both a PGP19-dependent and a PGP19-independent manner. Plant J

RIKEN Plant Science Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230 0045, Japan.
The Plant Journal (Impact Factor: 5.97). 03/2008; 53(3):516-29. DOI: 10.1111/j.1365-313X.2007.03358.x
Source: PubMed


Photoreceptors, phytochromes and cryptochromes regulate hypocotyl growth under specific conditions, by suppressing negative gravitropism, modulating phototropism and inhibiting elongation. Although these effects seem to be partially caused via the regulation of the phytohormone auxin, the molecular mechanisms underlying this process are still poorly understood. In our present study, we demonstrate that the flabby mutation enhances both phytochrome- and cryptochrome-inducible hypocotyl bending in Arabidopsis. The FLABBY gene encodes the ABC-type auxin transporter, PGP19, and its expression is suppressed by the activation of phytochromes and cryptochromes. Our current results therefore indicate that the phytochromes and cryptochromes have at least two effects upon the tropic responses of the hypocotyls in Arabidopsis: the enhancement of hypocotyl bending through the suppression of PGP19, and a PGP19-independent mechanism that induces hypocotyl bending. By the using an auxin polar transport assay and DR5:GUS expression analysis, we further find that the phytochromes inhibit basipetal auxin transport, and induce the asymmetric distribution of auxin in the hypocotyls. These data suggest that the control of auxin transport by phytochromes and cryptochromes is a critical regulatory component of hypocotyl growth in response to light.

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    • "Han et al. (2008) reported that red light pretreatment inhibits the blue light-dependent loss of phot1 from the plasma membrane . Nagashima et al. (2008a) showed that red light irradiation reduces the expression of ATP-BINDING CASSETTE subfamily B19 (ABCB19), which is an auxin efflux transporter known to be a negative regulator for phototropism (Noh et al., 2003; Nagashima et al., 2008b). Furthermore, ABCB19 is directly phosphorylated by phot1, resulting in the reduction of auxin transport (Christie et al., 2011). "
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    ABSTRACT: Several members of the AGCVIII kinase subfamily that includes PINOID (PID), PID2 and WAG proteins have previously been shown to phosphorylate PIN-FORMED (PIN) auxin transporters and control the auxin flow in plants. PID has been proposed as a key component of the phototropin (phot) signaling pathway that induces phototropic responses, although the responses were not significantly impaired in the pid single and pid wag1 wag2 triple mutants. This raises questions about the functional roles of the PID family in phototropic responses. Here, we investigated hypocotyl phototropism in the pid pid2 wag1 wag2 quadruple mutant in detail to clarify the roles of the PID family in Arabidopsis. The pid quadruple mutants exhibited moderate responses in continuous-light-induced phototropism with a decrease in growth rates of hypocotyls and normal responses in pulse-induced phototropism. On the other hand, it showed serious defects in enhancements of pulse-induced phototropic curvatures and lateral fluorescent auxin transport by red light pretreatment. Red light pretreatment significantly reduced the expression level of PID, and the constitutive expression of PID prevented pulse-induced phototropism irrespective of red light pretreatment. This suggests that the PID family plays a significant role in phytochrome-mediated phototropic enhancement, but not in the phot signaling pathway. Red light treatment enhanced the intracellular accumulation of PIN proteins in response to the vesicle-trafficking inhibitor brefeldin A, in addition to an increase of their expression levels. Taken together, these results suggest that red light preirradiation enhances phototropic curvatures by upregulation of PIN proteins, which are not being phosphorylated by the PID family.
    Full-text · Article · Oct 2014 · Plant physiology
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    • "Several studies of Arabidopsis mutant and transgenic lines expressing altered versions of one or both of the canonical crys, cry1 and cry2, have shown that cry function is required for normal phot1-dependent phototropic responsiveness (Lascève et al., 1999; Whippo and Hangarter, 2003; Ohgishi et al., 2004; Kang et al., 2008; Nagashima et al., 2008; Tsuchida-Mayama et al., 2010). The crys, like the phys with whom they work cooperatively for many light-regulated developmental responses, appear to function in large part through regulation of gene transcription (Kami et al., 2010; Liu et al., 2011). "
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    ABSTRACT: Phototropism, or the differential cell elongation exhibited by a plant organ in response to directional blue light, provides the plant with a means to optimize photosynthetic light capture in the aerial portion and water and nutrient acquisition in the roots. Tremendous advances have been made in our understanding of the molecular, biochemical, and cellular bases of phototropism in recent years. Six photoreceptors and their associated signaling pathways have been linked to phototropic responses under various conditions. Primary detection of directional light occurs at the plasma membrane, whereas secondary modulatory photoreception occurs in the cytoplasm and nucleus. Intracellular responses to light cues are processed to regulate cell-to-cell movement of auxin to allow establishment of a trans-organ gradient of the hormone. Photosignaling also impinges on the transcriptional regulation response established as a result of changes in local auxin concentrations. Three additional phytohormone signaling pathways have also been shown to influence phototropic responsiveness, and these pathways are influenced by the photoreceptor signaling as well. Here, we will discuss this complex dance of intra- and intercellular responses that are regulated by these many systems to give rise to a rapid and robust adaptation response observed as organ bending.
    Full-text · Article · Jan 2014 · The Plant Cell
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    • "Specifically, the regulation of PIN3 and perhaps other PIN genes could be part of a common set of intermediates between ABP1 and phyB. Consistent with this notion, the expression of ABCB19 is repressed by R although modes of interaction in shade of ABCB19 and PIN3 are unknown (Nagashima et al., 2008a, b). ABP1 regulates polar auxin transport at the organ level (Effendi et al., 2011) and by the regulation of PIN3 expression (Effendi and Scherer, 2011). "
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    ABSTRACT: The auxin receptor ABP1 directly regulates plasma membrane activities including the number of PIN-formed (PIN) proteins and auxin efflux transport. Red light (R) mediated by phytochromes regulates the steady-state level of ABP1 and auxin-inducible growth capacity in etiolated tissues but, until now, there has been no genetic proof that ABP1 and phytochrome regulation of elongation share a common mechanism for organ elongation. In far red (FR)-enriched light, hypocotyl lengths were larger in the abp1-5 and abp1/ABP1 mutants, but not in tir1-1, a null mutant of the TRANSPORT-INHIBITOR-RESPONSE1 auxin receptor. The polar auxin transport inhibitor naphthylphthalamic acid (NPA) decreased elongation in the low R:FR light-enriched white light (WL) condition more strongly than in the high red:FR light-enriched condition WL suggesting that auxin transport is an important condition for FR-induced elongation. The addition of NPA to hypocotyls grown in R- and FR-enriched light inhibited hypocotyl gravitropism to a greater extent in both abp1 mutants and in phyB-9 and phyA-211 than the wild-type hypocotyl, arguing for decreased phytochrome action in conjunction with auxin transport in abp1 mutants. Transcription of FR-enriched light-induced genes, including several genes regulated by auxin and shade, was reduced 3-5-fold in abp1-5 compared with Col and was very low in abp1/ABP1. In the phyB-9 mutant the expression of these reporter genes was 5–15-fold lower than in Col. In tir1-1 and the phyA-211 mutants shade-induced gene expression was greatly attenuated. Thus, ABP1 directly or indirectly participates in auxin and light signalling.
    Full-text · Article · Sep 2013 · Journal of Experimental Botany
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