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Noriyuki Suetsugu

Publications and source records attributed to Noriyuki Suetsugu.

9 recordsLinked to original sources
PubMed2007

Photometrical analysis with photosensory domains of photoreceptors in green algae.

Chloroplast photoorientation in the green alga Mougeotia scalaris is controlled by blue and red light. The properties of the LOV domains of phototropin A and B were consistent with previous data of action spectra and photoreceptor lifetime for blue light-mediated photoorientation. The LOV domains of the neochromes did not bind flavin, while the domains of neochrome 2 contributed to multimer formation. The absorption spectra of the neochrome phytochrome photosensory domain with phytochromobilin were very similar to the action spectra for red light-induced photoorientation. These results indicate that phototropin and neochrome work as the blue and red photoreceptors involved in photoorientation.

Algal Proteins↗
PubMed2006

Negative phototropic response of rhizoid cells in the fern Adiantum capillus-veneris.

In general, phototropic responses in land plants are induced by blue light and mediated by blue light receptor phototropins. In many cryptogam plants including the fern Adiantum capillus-veneris, however, red as well as blue light effectively induces a positive phototropic response in protonemal cells. In A. capillus-veneris, the red light effect on the tropistic response is mediated by phytochrome 3 (phy3), a chimeric photoreceptor of phytochrome and full-length phototropin. Here, we report red and blue light-induced negative phototropism in A. capillus-veneris rhizoid cells. Mutants deficient for phy3 lacked red light-induced negative phototropism, indicating that under red light, phy3 mediates negative phototropism in rhizoid cells, contrasting with its role in regulating positive phototropism in protonemal cells. Mutants for phy3 were also partially deficient in rhizoid blue light-induced negative phototropism, suggesting that phy3, in conjunction with phototropins, redundantly mediates the blue light response.

Adiantum↗
PubMed2005

A chimeric photoreceptor gene, NEOCHROME, has arisen twice during plant evolution.

Although most plant species from algae to flowering plants use blue light for inducing phototropism and chloroplast movement, many ferns, some mosses, and green algae use red as well as blue light for the regulation of these responses, resulting in better sensitivity at low light levels. During their evolution, ferns have created a chimeric photoreceptor (phy3 in Adiantum) between phytochrome (phy) and phototropin (phot) enabling them to use red light effectively. We have identified two genes resembling Adiantum PHY3, NEOCHROME1 and NEOCHROME2 (MsNEO1 and MsNEO2), in the green alga Mougeotia scalaris, a plant famous for its light-regulated chloroplast movement. Like Adiantum PHY3, both MsNEO gene products show phytochrome-typical bilin binding and red/far-red reversibility, the difference spectra matching the known action spectra of light-induced chloroplast movement in Mougeotia. Furthermore, both genes rescue red-light-induced chloroplast movement in Adiantum phy3 mutants, indicating functional equivalence. However, the fern and algal genes seem to have arisen independently in evolution, thus providing an intriguing example of convergent evolution.

Adiantum↗
PubMed2005

An auxilin-like J-domain protein, JAC1, regulates phototropin-mediated chloroplast movement in Arabidopsis.

The ambient-light conditions mediate chloroplast relocation in plant cells. Under the low-light conditions, chloroplasts accumulate in the light (accumulation response), while under the high-light conditions, they avoid the light (avoidance response). In Arabidopsis (Arabidopsis thaliana), the accumulation response is mediated by two blue-light receptors, termed phototropins (phot1 and phot2) that act redundantly, and the avoidance response is mediated by phot2 alone. A mutant, J-domain protein required for chloroplast accumulation response 1 (jac1), lacks the accumulation response under weak blue light but shows a normal avoidance response under strong blue light. In dark-adapted wild-type cells, chloroplasts accumulate on the bottom of cells. Both the jac1 and phot2 mutants are defective in this chloroplast movement in darkness. Positional cloning of JAC1 reveals that this gene encodes a J-domain protein, resembling clathrin-uncoating factor auxilin at its C terminus. The amounts of JAC1 transcripts and JAC1 proteins are not regulated by light and by phototropins. A green fluorescent protein-JAC1 fusion protein showed a similar localization pattern to green fluorescent protein alone in a transient expression assay using Arabidopsis mesophyll cells and onion (Allium cepa) epidermal cells, suggesting that the JAC1 protein may be a soluble cytosolic protein. Together, these results suggest that JAC1 is an essential component of phototropin-mediated chloroplast movement.

Amino Acid Sequence↗
PubMed2004

Plant organelle positioning.

Correct positioning and active movement of organelles within cells are essential for cellular homeostasis and adaptation to external stresses. Unlike animal and fungal systems, plant organelle positioning has not yet been revealed at the molecular level. The recent development of organelle-targeting green fluorescent protein (GFP) constructs and genetic analyses using Arabidopsis thaliana have shed new light on the field of plant organelle positioning, which has been found to be regulated by mechanisms that are similar to and/or distinct from those used by animals and fungi.

Actin Cytoskeleton↗
PubMed2003

Chloroplast unusual positioning1 is essential for proper chloroplast positioning.

The intracellular distribution of organelles is a crucial aspect of effective cell function. Chloroplasts change their intracellular positions to optimize photosynthetic activity in response to ambient light conditions. Through screening of mutants of Arabidopsis defective in chloroplast photorelocation movement, we isolated six mutant clones in which chloroplasts gathered at the bottom of the cells and did not distribute throughout cells. These mutants, termed chloroplast unusual positioning (chup), were shown to belong to a single genetic locus by complementation tests. Observation of the positioning of other organelles, such as mitochondria, peroxisomes, and nuclei, revealed that chloroplast positioning and movement are impaired specifically in this mutant, although peroxisomes are distributed along with chloroplasts. The CHUP1 gene encodes a novel protein containing multiple domains, including a coiled-coil domain, an actin binding domain, a Pro-rich region, and two Leu zipper domains. The N-terminal hydrophobic segment of CHUP1 was expressed transiently in leaf cells of Arabidopsis as a fusion protein with the green fluorescent protein. The fusion protein was targeted to envelope membranes of chloroplasts in mesophyll cells, suggesting that CHUP1 may localize in chloroplasts. A glutathione S-transferase fusion protein containing the actin binding domain of CHUP1 was found to bind F-actin in vitro. CHUP1 is a unique gene identified that encodes a protein required for organellar positioning and movement in plant cells.

Amino Acid Sequence↗
PubMedDate not supplied

Chloroplast avoidance movement reduces photodamage in plants.

When plants are exposed to light levels higher than those required for photosynthesis, reactive oxygen species are generated in the chloroplasts and cause photodamage. This can occur even under natural growth conditions. To mitigate photodamage, plants have developed several protective mechanisms. One is chloroplast avoidance movement, in which chloroplasts move from the cell surface to the side walls of cells under high light conditions, although experimental support is still awaited. Here, using different classes of mutant defective in chloroplast avoidance movement, we show that these mutants are more susceptible to damage in high light than wild-type plants. Damage of the photosynthetic apparatus and subsequent bleaching of leaf colour and necrosis occur faster under high light conditions in the mutants than in wild-type plants. We conclude that chloroplast avoidance movement actually decreases the amount of light absorption by chloroplasts, and might therefore be important to the survival of plants under natural growth conditions.

Antioxidants↗
PubMedDate not supplied

Phytochrome-dependent photomovement responses mediated by phototropin family proteins in cryptogam plants.

In this review, we describe the regulation of photomovement responses by phototropin and phytochrome photoreceptors. The blue light receptor phototropin mediates various photomovement responses such as phototropism, chloroplast movement and stomatal opening. In cryptogamic plants including ferns, mosses and green alga, red as well as blue light mediates phototropism and chloroplast movement. The red/far-red light reversibility suggests the involvement of phytochrome in these responses. Thereby, plant growth is presumably promoted by coordinating these photomovements to capture efficiently light for photosynthesis.

Chloroplasts↗