The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform

Ralf Reski - One of the best experts on this subject based on the ideXlab platform.

  • An integrated physiological and genetic approach to the dynamics of FtsZ targeting and organisation in a moss, Physcomitrella patens
    Protoplasma, 2007
    Co-Authors: I. Suppanz, Eric Sarnighausen, Ralf Reski
    Abstract:

    Plant FtsZ (filamentous temperature-sensitive Z) proteins are regarded as descendants of prokaryotic cell division proteins. We could show previously that four FtsZ isoforms of the moss Physcomitrella patens assemble into, and interact in, distinct structures inside the Chloroplasts and in the cytosol. Their organisation and localisation patterns indicate an involvement in chloroplast and cell division and in the maintenance of chloroplast shape and integrity. The cellular processes of chloroplast division and maintenance of chloroplast shape were disturbed either by application of the beta-lactam antibiotic ampicillin or by a mutation that presumably affects signal transduction of the plant hormone cytokinin. When cells of these plants were analysed microscopically, there was no indication that cytosolic functions of FtsZ proteins were affected. Furthermore, FtsZ proteins continued to build three-dimensional plastoskeleton networks, even in considerably enlarged or malformed Chloroplasts. On the other hand, macrochloroplast formation promoted the localisation of FtsZ proteins in filaments that emanate from the plastids and, therefore, most likely represent stromules. Annular FtsZ structures that are regarded as essential components of the division apparatus were absent from macroChloroplasts of ampicillin-treated cells. Thus, the distribution of FtsZ proteins after inhibition of chloroplast division further strengthens our hypothesis on the functions of distinct isoforms. In addition, the results provide further insight into the regulation of protein targeting and dynamics of plastoskeletal elements.

Yanda Li - One of the best experts on this subject based on the ideXlab platform.

  • CURE-Chloroplast: a chloroplast C-to-U RNA editing predictor for seed plants.
    BMC bioinformatics, 2009
    Co-Authors: Pufeng Du, Liyan Jia, Yanda Li
    Abstract:

    BACKGROUND: RNA editing is a type of post-transcriptional modification of RNA and belongs to the class of mechanisms that contribute to the complexity of transcriptomes. C-to-U RNA editing is commonly observed in plant mitochondria and Chloroplasts. The in vivo mechanism of recognizing C-to-U RNA editing sites is still unknown. In recent years, many efforts have been made to computationally predict C-to-U RNA editing sites in the mitochondria of seed plants, but there is still no algorithm available for C-to-U RNA editing site prediction in the Chloroplasts of seed plants. RESULTS: In this paper, we extend our algorithm CURE, which can accurately predict the C-to-U RNA editing sites in mitochondria, to predict C-to-U RNA editing sites in the Chloroplasts of seed plants. The algorithm achieves over 80% sensitivity and over 99% specificity. We implement the algorithm as an online service called CURE-Chloroplast http://bioinfo.au.tsinghua.edu.cn/pure. CONCLUSION: CURE-Chloroplast is an online service for predicting the C-to-U RNA editing sites in the Chloroplasts of seed plants. The online service allows the processing of entire chloroplast genome sequences. Since CURE-Chloroplast performs very well, it could be a helpful tool in the study of C-to-U RNA editing in the Chloroplasts of seed plants.

Masamitsu Wada - One of the best experts on this subject based on the ideXlab platform.

  • Phototropin2 Contributes to the Chloroplast Avoidance Response at the Chloroplast-Plasma Membrane Interface.
    Plant Physiology, 2020
    Co-Authors: Kazuhiro Ishishita, Masato Nakai, Takeshi Higa, Hidekazu Tanaka, Shin-ichiro Inoue, Aeri Chung, Tomokazu Ushijima, Tomonao Matsushita, Toshinori Kinoshita, Masamitsu Wada
    Abstract:

    Blue-light-induced chloroplast movements play an important role in maximizing light utilization for photosynthesis in plants. Under a weak light condition, Chloroplasts accumulate to the cell surface to capture light efficiently (chloroplast accumulation response). Conversely, Chloroplasts escape from strong light and move to the side wall to reduce photodamage (chloroplast avoidance response). The blue light receptor phototropin (phot) regulates these chloroplast movements and optimizes leaf photosynthesis by controlling other responses in addition to chloroplast movements. Seed plants such as Arabidopsis (Arabidopsis thaliana) have phot1 and phot2. They redundantly mediate phototropism, stomatal opening, leaf flattening, and the chloroplast accumulation response. However, the chloroplast avoidance response is induced by strong blue light and regulated primarily by phot2. Phots are localized mainly on the plasma membrane. However, a substantial amount of phot2 resides on the chloroplast outer envelope. Therefore, differentially localized phot2 might have different functions. To determine the functions of plasma membrane- and chloroplast envelope-localized phot2, we tethered it to these structures with their respective targeting signals. Plasma membrane-localized phot2 regulated phototropism, leaf flattening, stomatal opening, and chloroplast movements. Chloroplast envelope-localized phot2 failed to mediate phototropism, leaf flattening, and the chloroplast accumulation response but partially regulated the chloroplast avoidance response and stomatal opening. Based on the present and previous findings, we propose that phot2 localized at the interface between the plasma membrane and the Chloroplasts is required for the chloroplast avoidance response and possibly for stomatal opening as well.

  • Chloroplast Actin Filaments Involved in Chloroplast Photorelocation Movements
    The Cytoskeleton, 2019
    Co-Authors: Masamitsu Wada, Sam-geun Kong
    Abstract:

    Plants have evolved sophisticated mechanisms to survive in various environmental changes. Chloroplast movement is an essential response to optimize photosynthesis and to avoid photodamage under fluctuating light conditions. Chloroplasts accumulate at periclinal walls to maximize light absorption under weak light while they move to anticlinal walls to minimize light exposure under strong light. The light strength is monitored by blue light receptor phototropins in general. In Arabidopsis thaliana, both phototropin1 (phot1) and phototropin2 (phot2) are involved in accumulation response, but phot2 is specifically involved in avoidance response. Such appropriate photorelocation movements of Chloroplasts are mediated by a structure made of short actin filaments specialized for chloroplast movement. The short actin filaments are dynamically reorganized on the leading edges of moving Chloroplasts, so that named chloroplast actin (cp-actin) filaments. In this chapter, we summarize recent knowledge about cp-actin filaments and next challenges to elucidate the underlying mechanisms.

  • Chloroplast Photorelocation Movement: A Sophisticated Strategy for Chloroplasts to Perform Efficient Photosynthesis
    Advances in Photosynthesis - Fundamental Aspects, 2012
    Co-Authors: Noriyuki Suetsugu, Masamitsu Wada
    Abstract:

    Fig. 1. Typical intracellular distribution pattern of Chloroplasts by their photorelocation movement. In darkness, Chloroplasts are located on the cell bottom in Arabidopsis thaliana. Note that the dark position varies among plant species. Weak light induces the chloroplast accumulation response along the peliclinal walls so that Chloroplasts can perceive light efficiently. Strong light induces the chloroplast avoidance response toward the anticlinal walls to reduce photodamage.

  • Chloroplast actin filaments organize meshwork on the photorelocated Chloroplasts in the moss Physcomitrella patens
    Planta, 2010
    Co-Authors: Hiroko Yamashita, Masamitsu Wada, Takatoshi Kagawa, Takeshi Kanegae, Yoshikatsu Sato, Akeo Kadota
    Abstract:

    Cytoskeleton dynamics during phototropin-dependent chloroplast photorelocation movement was analyzed in protonemal cells of actin- and microtubule-visualized lines of Physcomitrella patens expressing GFP- or tdTomato-talin and GFP-tubulin. Using newly developed epi- and trans-microbeam irradiation systems that permit fluorescence observation of the cell under blue microbeam irradiation inducing chloroplast relocation, it was revealed that meshwork of actin filaments formed at the chloroplast-accumulating area both in the avoidance and accumulation movements. The structure disappeared soon when blue microbeam was turned off, and it was not induced under red microbeam irradiation that did not evoke chloroplast relocation movement. In contrast, no apparent change in microtubule organization was detected during the movements. The actin meshwork was composed of short actin filaments distinct from the cytoplasmic long actin cables and was present between the Chloroplasts and plasma membrane. The short actin filaments emerged from around the chloroplast periphery towards the center of chloroplast. Showing highly dynamic behavior, the chloroplast actin filaments (cp-actin filaments) were rapidly organized into meshwork on the chloroplast surface facing plasma membrane. The actin filament configuration on a chloroplast led to the formation of actin meshwork area in the cell as the Chloroplasts arrived at and occupied the area. After establishment of the meshwork, cp-actin filaments were still highly dynamic, showing appearance, disappearance, severing and bundling of filaments. These results indicate that the cp-actin filaments have significant roles in the chloroplast movement and positioning in the cell.

  • Chloroplast Outer Envelope Protein CHUP1 Is Essential for Chloroplast Anchorage to the Plasma Membrane and Chloroplast Movement
    Plant Physiology, 2008
    Co-Authors: Kazusato Oikawa, Akihiro Yamasato, Sam-geun Kong, Masahiro Kasahara, Masato Nakai, Fumio Takahashi, Yasunobu Ogura, Takatoshi Kagawa, Masamitsu Wada
    Abstract:

    Chloroplasts change their intracellular distribution in response to light intensity. Previously, we isolated the chloroplast unusual positioning1 (chup1) mutant of Arabidopsis (Arabidopsis thaliana). This mutant is defective in normal chloroplast relocation movement and shows aggregation of Chloroplasts at the bottom of palisade mesophyll cells. The isolated gene encodes a protein with an actin-binding motif. Here, we used biochemical analyses to determine the subcellular localization of full-length CHUP1 on the chloroplast outer envelope. A CHUP1-green fluorescent protein (GFP) fusion, which was detected at the outermost part of mesophyll cell Chloroplasts, complemented the chup1 phenotype, but GFP-CHUP1, which was localized mainly in the cytosol, did not. Overexpression of the N-terminal hydrophobic region (NtHR) of CHUP1 fused with GFP (NtHR-GFP) induced a chup1-like phenotype, indicating a dominant-negative effect on chloroplast relocation movement. A similar pattern was found in chloroplast OUTER ENVELOPE PROTEIN7 (OEP7)-GFP transformants, and a protein containing OEP7 in place of NtHR complemented the mutant phenotype. Physiological analyses of transgenic Arabidopsis plants expressing truncated CHUP1 in a chup1 mutant background and cytoskeletal inhibitor experiments showed that the coiled-coil region of CHUP1 anchors Chloroplasts firmly on the plasma membrane, consistent with the localization of coiled-coil GFP on the plasma membrane. Thus, CHUP1 localization on Chloroplasts, with the N terminus inserted into the chloroplast outer envelope and the C terminus facing the cytosol, is essential for CHUP1 function, and the coiled-coil region of CHUP1 prevents chloroplast aggregation and participates in chloroplast relocation movement.

Michael Hippler - One of the best experts on this subject based on the ideXlab platform.

  • The chloroplast proteome: a survey from the Chlamydomonas reinhardtii perspective with a focus on distinctive features
    Current Genetics, 2011
    Co-Authors: Mia Terashima, Michael Specht, Michael Hippler
    Abstract:

    The unicellular green alga Chlamydomonas reinhardtii has emerged to be an important model organism for the study of oxygenic eukaryotic photosynthesis as well as other processes occurring in the chloroplast. However, the chloroplast proteome in C.   reinhardtii has only recently been comprehensively characterized, made possible by proteomics emerging as an accessible and powerful tool over the last decade. In this review, we introduce a compiled list of 996 experimentally chloroplast-localized proteins for C.   reinhardtii , stemming largely from our previous proteomic dataset comparing Chloroplasts and mitochondria samples to localize proteins. In order to get a taste of some cellular functions taking place in the C.   reinhardtii chloroplast, we will focus this review particularly on metabolic differences between Chloroplasts of C.   reinhardtii and higher plants. Areas that will be covered are photosynthesis, chlorophyll biosynthesis, carbon metabolism, fermentative metabolism, ferredoxins and ferredoxin-interacting proteins.

Hunseung Kang - One of the best experts on this subject based on the ideXlab platform.

  • PRBP plays a role in plastid ribosomal RNA maturation and chloroplast biogenesis in Nicotiana benthamiana
    Planta, 2011
    Co-Authors: Yong-joon Park, Hyun Ju Jung, Hunseung Kang
    Abstract:

    In the present study, we investigated protein characteristics and physiological functions of PRBP (plastid RNA-binding protein) in Nicotiana benthamiana . PRBP fused to green fluorescent protein (GFP) localized to the Chloroplasts. Recombinant PRBP proteins bind to single-stranded RNA in vitro, but not to DNA in a double- or a single-stranded form. Virus-induced gene silencing (VIGS) of PRBP resulted in leaf yellowing in N. benthamiana . At the cellular level, PRBP depletion disrupted chloroplast biogenesis: chloroplast number and size were reduced, and the thylakoid membrane was poorly developed. In PRBP -silenced leaves, protein levels of plastid-encoded genes were significantly reduced, whereas their mRNA levels were normal regardless of their promoter types indicating that PRBP deficiency primarily affects translational or post-translational processes. Depletion of PRBP impaired processing of the plastid-encoded 4.5S ribosomal RNA, resulting in accumulation of the larger precursor rRNAs in the Chloroplasts. In addition, PRBP-deficient Chloroplasts contained significantly reduced levels of mature 4.5S and 5S rRNAs in the polysomal fractions, indicating decreased chloroplast translation. These results suggest that PRBP plays a role in chloroplast rRNA processing and chloroplast development in higher plants.