In C4 plants, the carbon dioxide fixation takes places twice (one in mesophyll cells, second in bundle sheath cells). Transverse sections were stained in PME buffer (50 mM PIPES-NaOH, pH 6.9, 5 mM MgSO4, 5 mM EGTA and 0.15 M NaCl) containing 1 μM rhodamine 123 for 4 min. C4 plants such as maize and finger millet have two types of photosynthetic cells, mesophyll (M) and bundle sheath (BS). After 2 h of strong light irradiation, maize M chloroplasts redistributed, but were found along the sides of anticlinal walls parallel to the direction of irradiation (Fig. 2008). 2009 Oct;50(10):1736-49. doi: 10.1093/pcp/pcp116. In each panel, the upper side of the leaf sections is the adaxial side. Clumping of chloroplasts in response to water stress was first found in cortical cells of P. grandiflora stems (Guralnick et al. After floating on the same solution for 16 h under low light (100 μmol m−2 s−1), the leaf segments were hand-sectioned with a razor blade and transverse sections were observed with a light microscope. The intracellular positions of neither type of mitochondria were changed regardless of salinity stress. However, only mesophyll chloroplasts can change their positions in response to environmental stresses. Light-dependent intracellular positioning of mitochondria in, Blue light-dependent nuclear positioning in. A change in the intracellular disposition of C4 chloroplasts in response to environmental stresses other than light was initially reported by Lal and Edwards (1996). | 2017 Jan;40(1):80-94. doi: 10.1111/pce.12834. Water potential was measured for 12 d after disruption of the water supply. We characterized protein phosphorylation in thylakoids of the two cell types from maize grown under either low or high light. Moreover, growth conditions might be another factor to yield the differential light responsiveness. NIH HHS (A) Control; (B) ABA treatment. Treatment of finger millet leaf segments with ABA induced the centripetal assembly of M chloroplasts in a light-dependent manner (Fig. 2005). Indeed, it was reported that hydrogen peroxide is generated by high fluence blue light in Arabidopsis M cells and was suggested to promote chloroplast avoidance movement in the presence of blue light (Wen et al. Leaves in C4 plants such as maize (Zea mays) form a classical Kranz leaf anatomy during their development (Edwards and Walker, 1983; Nelson and Langdale, 1992). Plasmodesmata are intercellular channels that facilitate molecular diffusion between neighboring plant cells. 2004). 2006). 6). Regulation of photosynthesis and antioxidant metabolism in maize leaves at optimal and chilling temperatures: review. For nuclear staining, leaf segments from the salinity-stressed plants were fixed as described above and transverse sections were stained with 1 mg ml−1 4′,6-diamidino-2-phenylindole (DAPI) for 1 h. After washing with distilled water for 10 min twice, the sections were imaged with a light microscope (BX51, Olympus) equipped with an epifluorescence system (U-LH100HG, Olympus). Both cell types are arranged into a specialized Kranz-type leaf anatomy: BS cells surround the vascular tissues while M cells encircle the cylinders of the BS cells. Compared with the NAD-ME type finger millet, maize has more numerous M chloroplasts, while its BS chloroplasts are smaller and located in the centrifugal position (Fig. To gain a better understanding of chloroplast relocation movement in C4 plants, we closely investigated the intracellular disposition of chloroplasts in response to various environmental stresses and plant hormones in this study. The motility and positioning of chloroplasts appear to be mediated by actin filaments and/or microtubules (Wada et al. For other chemical treatments, small leaf segments were excised and vacuum infiltrated for 10 min with 10 mM MES-KOH (pH 6.9) containing IAA (0.3, 1 or 3 μM), 2,4-D (3, 10 or 30 μM), GA3 (15, 50 or 150 μM), kinetin (30, 100 or 300 μM), ABA (1, 3, 10 or 30 μM), NaCl [0.3, 1 or 3% (w/v)] or H2O2 (1, 5, 10, 20 or 100 mM). Photosynthetic and anatomical characteristics in the C, Differential sensitivity of chloroplasts in mesophyll and bundle sheath cells in maize, an NADP-malic enzyme-type C, Occurrence of the suberized lamella in leaves of grasses of different photosynthetic types.I. Although supplying plant roots with 20% polyethylene glycol solution induced re-arrangement of M chloroplasts (Fig. To investigate the possibility of the involvement of ABA in the chloroplast movement in response to environmental stresses, we allowed leaf segments from non-stressed finger millet to absorb ABA during incubation for 16 h under low intensity light. C 4 plants have two types of photosynthetic cells: mesophyll and bundle sheath cells. This ABA treatment induced the centripetal assembly of M chloroplasts (Fig. Finger millet growing under the normal light condition (500 μmol m−2 s−1 during the light period) was exposed to drought stress by withholding the water supply. C and F are enlarged images of M cells, and the right side in the two panels is the BS side. The water potentials of non-stressed plants were –0.58 to –0.15 MPa. 4C). For ABA treatment, small leaf segments were excised and vacuum infiltrated for 10 min with 0.1% (v/v) ethanol with or without 10 μM ABA. The aggregative movement of M chloroplasts occurred at normal light intensities (250–500 μmol m−2 s−1) in response to environmental stresses, such as drought, salinity and hyperosmosis. 6, 7). Under these conditions, the assemblage of M chloroplasts is thought to provide photoprotection through mutual shading of the chloroplasts, similarly to C3 chloroplasts. 1997, Foyer et al. The C4 grass Zea mays separates light and light-independent photosynthetic processes into two leaf cell types: bundle sheath (BS) and mesophyll (M). Only the M chloroplasts showed a change in intracellular positioning in response to high osmotic stress, similarly to the salinity stress. 2009). Moreover, the distribution of antioxidant enzymes is reported to be different between M and BS cells in maize (Doulis et al. 2002). B, bundle sheath cell; M, mesophyll cell; V, vascular bundle. This generates high metabolic fluxes between these cells, through interconnecting plasmodesmata (PD). In the bundle sheath cells, OAA … This generates high metabolic fluxes between these cells, through interconnecting plasmodesmata (PD). The centrifugal position of BS chloroplasts is advantageous to metabolite exchange between M cells and BS chloroplasts. A study with Arabidopsis mutants revealed that chloroplast avoidance movement decreases the amount of light absorption by chloroplasts, and therefore protects plants from photodamage under high light (Kasahara et al. This anatomical pattern consists of a radial arrangement of chloren- chyma around vascular bundles. and EowARDS, 1973 a, b, c). S3). When mature, BS and M cells have anatomically and biochemically distinct chloroplasts that must cooperate to complete the process of photosynthesis. The C4 M chloroplast movement may be one means of photoprotection which occurs prior to photoinhibition. Although BS nuclei were located close to M cells, M nuclei were distributed peripherally at the mid position, a little towards BS cells. C4 plants have 2 types of photosynthetic cells: mesophyll and bundle sheath cells. Moreover, the re-arrangement of M chloroplasts was observed in field-grown C4 plants when exposed to mid-day sunlight, but also under midsummer drought conditions. The photosynthetic photon flux density at the leaf surface was checked with a quantum meter (LI-250, LI-COR, Lincoln, NE, USA). 9: In C3 plants, the carbon dioxide fixation takes place only at one place. Another possible role of C4 M chloroplast movement is maintenance of photosynthetic activity under stress conditions. 10: C3 plants possess only one CO2 acceptor. 2020 Jan 9;20(1):17. doi: 10.1186/s12870-019-2219-7. The aggregative movement of M chloroplasts in salinity-stressed plants was also observed in semi-thin sections prepared from resin-embedded leaves (Supplementary Fig. Mesophyll chloroplasts are randomly distributed along cell walls, whereas bundle sheath chloroplasts are located close to the vascular tissues or mesophyll cells depending on the plant species. Differential localization of antioxidants in maize leaves. Unlike C3 grasses, C4 grasses have leaves. Change in the intracellular positions of maize chloroplasts in response to light irradiation. For cytochalasin treatment, small leaf segments (5 × 5 mm square) were excised and vacuum infiltrated for 10 min with 0.5% (v/v) DMSO with or without 50 μM cytochalasin B (MP Biomedicals, Irvine, CA, USA). Clipboard, Search History, and several other advanced features are temporarily unavailable. In contrast, the centripetal position of BS chloroplasts maximizes the length of the CO2 diffusion pathway between BS and M cells, and minimizes CO2 leakage from BS cells to M cells (Hattersley and Browning 1981, von Caemmerer and Furbank 2003). Li H, Bai M, Jiang X, Shen R, Wang H, Wang H, Wu H. BMC Plant Biol. Actin filaments not only provide tracks for chloroplast movement but also anchor the chloroplasts after photo-orientation (Takagi 2003). Therefore, it is thought that some signal associated with the osmotic stress is generated in a domain outside of leaf tissue and influences M chloroplast movement. C3 plants are generally grown under lower intensity light compared with C4 plants and, therefore, photoinhibition and chloroplast movement for photoprotection in C3 plants is more likely to occur at relatively low light intensities. In contrast, the extent of chloroplast movement was low after 30 min of high intensity light irradiation (Fig. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. My lecturer said that CAM plants only have mesophyll plants. For microscopic observation of semi-thin sections, leaf segments were fixed as previously reported (Omoto et al. COVID-19 is an emerging, rapidly evolving situation. Mitochondria (yellow) and chloroplasts (red) were imaged using confocal laser scanning microscopy. This site needs JavaScript to work properly. Effect of cytochalasin B on the intracellular arrangement of chloroplasts in response to light irradiation. These abiotic stresses are thought to reduce the threshold intensity of light at which aggregative movement of M chloroplasts occurs. Because ABA was vacuum infiltrated into the leaf segments, M chloroplast movement is thought to be caused by a direct effect of ABA on M cells and not by secondary effects such as stomatal closure. 4, 5). As C4 M chloroplasts move toward the BS side, the M cells might possess a system for determining cell polarity and machinery for polarized motility. Reactive oxygen species and redox regulation in mesophyll and bundle sheath cells of C4 plants. | The leaf surface at that time was exposed to a light intensity of about 1,800 μmol m−2 s−1, which was not high enough to induce chloroplast movement in the laboratory. 5). A potent inhibitor of actin polymerization, cytochalasin B, inhibited the aggregative movement of M chloroplasts in response to high intensity light (Fig. 2009). 10). Chloroplast photorelocation movement is extensively studied in C3 but not C4 plants. 1975 Nov; 171 (1):214–225. Transverse sections of leaf blades from control (A–C) or salinity-stressed (D–F) plants were stained with rhodamine 123. S1). Construction of the sophisticated plasmodesmata was linked to C4 photosynthesis, and plasmodesmata assembly finished more rapidly in maize mutants with defective C4 pathways than in wild-type plants. Moreover, leakiness of CO2 from BS cells is increased in stressed C4 plants (Ghannoum 2009). Chlorophyll fluorescence was measured with a portable chlorophyll fluorometer PAM-2100 (Walz, Effeltrich, Germany). 2, Supplementary Fig. The bundle sheath also conducts the flo… Actin filaments encircle M and BS chloroplasts of finger millet and maize, and seem to be involved in their positioning and anchorage (Kobayashi et al. When the water potential was between –0.53 and –0.15 MPa, chloroplast movement was observed in some sections but not in others. Scale bars = 50 μm. Autofluorescence of chloroplasts was excited with the 543 nm wavelength of a HeNe laser and imaged using an LP560 longpass filter. Inoue and Shibata (1974) reported that absorbance of leaves from five graminaceous C4 species decreased in response to blue light (about 86 μmol quanta m−2 s−1), but the light intensity was much lower than that necessary for the obvious aggregative movement induced by white light in our experiment. 2003). Various concentrations of NaCl (0.3–3%) and H2O2 (1–100 mM) also had no effect (data not shown). Search for other works by this author on: Crop production in artificial solutions and soils with special reference to factors influencing yield and absorption of inorganic nutrients. In contrast, the centripetal arrangement of BS chloroplasts was unchanged, even though they appeared to swell slightly after strong light illumination and the degree of chloroplast association was marginally reduced. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. The chloroplast movement in M cells of finger millet occurred under normal intensity light (500 μmol m−2 s−1) under stress conditions such as drought, salinity or hyperosmosis (Figs. 2. Therefore, there is a possibility that some stress provoked by photoinhibition acts as a trigger for the aggregative movement of M chloroplasts, in addition to the possibility that strong light itself functions as a signal. 8). These unique arrangements of C4 chloroplasts are thought to be caused by the cytoskeletal network and vacuolar pressure (Kobayashi et al. These chloroplast photo-relocation movements are widely observed in a variety of plant species, from green algae to seed plants, although little attention has been given to C4 plants. To induce drought stress, water supply was withheld from finger millet plants growing under normal intensity light (500 μmol m−2 s−1). 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