• Proceedings of the Zoological Society Korea Conference
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• 2001.10a
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• pp.91-91
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• 2001

No Abstract, See Full Text

• Rapid Communication in Photoscience
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• v.3 no.3
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• pp.53-55
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• 2014

The shade avoidance syndrome is a morphological and physiological response when plants are exposed to shade. Recent work in Arabidopsis had begun to define the molecular components of the shade avoidance syndrome in dicotyledonous model plant. However, little is known about the shade avoidance response networks in agriculturally important monocotyledon crops such as rice. Here, we found that the degree of bending at the lamina joint is inversely proportional to the R:FR ratio. To elucidate which phytochrome is involved in this response, we did lamina joint inclination assay with the rice phytochrome-deficient mutants (osphyA, osphyB, and osphyC) and the wild type plants. Whereas the osphyA and osphyC knockout mutants bent at the lamina joint in the far-red rich condition as the wild type plants, the osphyB knockout mutants no longer bent at the lamina joint in the far-red rich condition. These results suggest that PHYB acts as a sole photoreceptor in the lamina joint inclination response in rice.

• Journal of Life Science
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• v.28 no.1
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• pp.9-16
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• 2018

Light is essential to the growth and development of plants, and it is perceived by phytochromes, which are one of the photoreceptors that regulate physiological responses in plants. Ethylene regulates the dormancy, senescence, growth, and development of organs in plants. This research focused on the interaction of phytochromes and ethylene to control hypocotyl growth and gravitropism using phytochrome mutants of Arabidopsis, phyA, phyB, and phyAB, under three light conditions: red (R) light, farred (FR) light, and white light. The mutant phyAB exhibited the most stimulation of gravitropic response of all three phytochrome mutants and wild type (WT) in all three light conditions. Moreover, phyB in the R light condition showed more negative gravitropism than phyA. However, phyB in the FR light condition showed less curvature than phyA. The hypocotyl growth pattern was similar to the gravitropic response in several light conditions. To explain the mechanism of the regulation of gravitropic response and growth, we measured the ethylene production and activities of in vitro ACS and ACO. Ethylene production was reduced in all the mutants grown in white light in comparison to the WT. Ethylene production increased in the phyA grown in R light and phyB grown in FR light in comparison to the other mutants. The ACS activity coincided with the ethylene production in the phyA and the phyB grown in R light and FR light, respectively. These results suggest that the Pfr form of phyB in R light and the Pr form of phyA in FR light increased ethylene production via increasing ACS activity.

• Journal of Integrative Natural Science
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• v.1 no.1
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• pp.24-31
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• 2008

Brassinosteroids (BRs) are a special class of plant steroid hormones that are essential for normal growth and development. Part of confusion is whether BRs are unique to plants, because they have overlapping physiological roles with other better-studied hormones and with physiological responses caused by light. In systems designed to assay for cytokinins, the effects of BRs vary. We measured hypocotyl length for testing the ability of brassinolide (BL) to rescue double mutant between det2 and the photoreceptor null mutant phytochrome B (phyB). PHYB involved in controlling hypocotyl elongation in increased concentration of BL whereas phyBdet2 double mutant just partially rescue to phyB in white and red light indicated the involvement of BRs in PHYB regulated cell elongation. BRs regulated hypocotyl growth was delayed by BAP, a cytokinin treatment but inhibitory effects of BAPs on hypocotyl growth was slightly recovered by BL. The result indicated that the mode of action of BR and cytokinin is independent or sequential in the downstream light-regulated response control on hypocotyl elongation and also light modulated the action of BR and cytokinin in some extent.

• Proceedings of the Botanical Society of Korea Conference
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• 1987.07a
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• pp.63-79
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• 1987

Light regulates a variety of genes in higher plants. The expression of light-induced plant genes is regulated at the level of transcription via red- light photomorphogenic receptor, phytochrome, as well as unknown blue light photoreceptor(s). Ribulose-5-phosphate carboxylase/oxygenase (Rubisco) small subunit (SSB) and light harvesting chlorophyll a/b (Cab) protein are those of the best understood genes regulated by light. 5'-upstream flanking sequence (- -400) of Rubisco SSB and Cab genes sis known as a light responsive, enhance-like element. It responses to red and blue light in transgenic plant system as a tissue specific manner. Phytochrome gene is also regulated by light. In contrast to most of the light regulated plant genes, it is negatively controlled by red light. Search for the cis- and trans-acting factors responsible for the light signal is in progress to understant photomorphogenesis and development in higher plants.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.10a
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• pp.32-32
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• 2017

• Interdisciplinary Bio Central
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• v.1 no.1
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• pp.1.1-1.5
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• 2009

Many organisms control their physiology and behavior in response to the local light environment, which is first perceived by photoreceptors that undergo light-dependent conformational changes. Phytochromes are one of the major photoreceptors in plants, controlling wide aspects of plant physiology by recognizing the light in red (R) and far-red (FR) spectra. Higher plants have two types of phytochromes; the photo-labile type I (phyA in Arabidopsis) and photo-stable type II (phyB-E in Arabidopsis). Phytochrome B (phyB), a member of the type II phytochromes in Arabidopsis, shows classical R and FR reversibility between the inter-convertible photoisomers, Pr and Pfr. Interestingly, the Pr and Pfr isomers show partitioning in the cytosol and nucleus, respectively. In the over 50 years since its discovery, it has been thought that the type II phytochromes only function to mediate R light. As described in the text, we have now discovered phyB has an active function in FR light. Even striking is that the R and FR light exert an opposite effect. Thus, FR light is not simply nullifying the R effect but has an opposing effect to R light. What is more interesting is that the phyB-mediated actions of FR and R light occur at different cellular compartment of the plant cell, cytosol and nucleus, respectively, which was proven through utilization of the cytosolic and nuclear-localized mutant versions of phyB. Our observations thus shoot down a major dogma in plant physiology and will be considered highly provocative in phytochrome function. We argue that it would make much more sense that plants utilize the two isoforms rather than only one form, to effectively monitor the changing environmental light information and to incorporate the information into their developmental programs.

• Proceedings of the Korean Society of Potoscience Conference
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• spring
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• pp.97-103
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• 2003

Phytochrome controls diverse aspects of plant development in response to the ambient light conditions. HFRl, a basic helix-loop-helix protein, is required for a subset of phytochrome A (phy A)-mediated photo-responses in Arabidopsis. Here, we show that overexpression of HFR1-N105, but not the one of the full-length HFR1, confers exaggerated photo-responses. The transgenic plants overexpressing HFR1- N105 exhibited light-independence in a subset of photo-responses, including germination, de-etiolation, gravitropic hypocotyl growth, and blocking of greening. Overexpression of HFR1-N105 also caused constitutive light-responses in the expression of some light-regulated genes. In addition, the HFR1-N105 overexpressor showed hypersensitive responses under R and FR light, dependently on phyB and phyA, respectively. End-of-day far-red light response and petiole elongation were suppressed in the HFR1-N105 overexpressor plants. Together these results imply that overexpression of HFR1-N105 activated a branch of light signaling, supporting the hypothesis that transcriptional regulation in the nucleus would be the primary mechanism of light signaling in Arabidopsis. We discuss the biotechnological potential of the mutant bHLH protein, HFR1-N105 in regard to suppressed shade avoidance syndrome.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.2
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• pp.71-76
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• 1998

To define the relations between endogenous GA levels and growth and flowering in short-day plant sorghum, growth retardant BX-112 was applied to two sorghum genotypes, wild-type and phytochrome B mutant (phyB-1), which grows faster and flowers earlier than the wild-type. BX-112 and $GA_3$ were applied as a soil drench, and plant height, culm length, and date to floral initiation were investigated. Endogenous GAs contents were measured with GC-MS-SIM. BX-112 treatments inhibited shoot growth in both genotypes and drastically reduced $GA_1$ and $GA_8$ levels. With increasing BX-112 concentrations, $GA_1$ concentrations declined linearly, but caused the accumulation of intermediates from $GA_12$ to $GA_20$. This result implies that $GA_1$ is the major active endogenous GA in shoot elongation in a short day plant sorghum. The inhibition of plant growth in both of wild type and phyB-1 by BX-112 was very similar, while BX-112 effects on floral initiation in two types of plants differed significantly. Floral initiation of phyB-1 was not affected by BX-1l2, but that of wild-type was delayed as BX-1l2 concentration increased. Because BX-112 treatment causes accumulation of biosynthetic intermediates between synthetic pathway from $GA_12$ to $GA_20$ and because phyB-1 is altered in GA metabolism in this same region of the early C13-hydroxylation pathway, BX-112 may fail to block flowering of phyB-1.

• BMB Reports
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• v.32 no.3
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• pp.215-225
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• 1999

Phytochromes (with gene family members phyA, B, C, D, and E) are a wavelength-dependent light sensor or switch for gene regulation that underscore a number of photo responsive developmental and morphogenic processes in plants. Recently, phytochrome-like pigment proteins have also been discovered in prokaryotes, possibly functioning as an auto-phosphorylating/phosphate-relaying two-component signaling system (Yeh et al., 1997). Phytochromes are photochromically convertible between the light sensing Pr and regulatory active Pfr forms. Red light converts Pr to Pfr, the latter having a "switch-on" conformation. The Pfr form triggers signal transduction pathways to the downstream responses including the expression of photosynthetic and other growth-regulating genes. The components involved in and the molecular mechanisms of the light signal transduction pathways are largely unknown, although G-proteins, protein kinases, and secondary messengers such as $Ca^{2+}$ ions and cGMP are implicated. The 124-127 kDa phytochromes form homodimeric structures. The N-terminal half contains the tetrapyrrolic phytochromobilin for red/far-red light absorption. The C-terminal half includes both a dimerization motif and regulatory box where the red light signal perceived by the chromophore-domain is recognized and transduced to initiate the signal transduction cascade. A working model for the inter-domain signal communication within the phytochrome molecule is proposed in this Review.