Changes in the density of microtubular networks in mesophyll cells and mesophyll derived protoplasts of Nicotiana and Triticum during leaf development

Changes in the plastid ultrastructure during development of a leaf have been studied extensively. Most studies have been done on the development of chloroplasts in mesophyll cells. Chloroplasts are small and few in number or plastids never develop into chloroplasts in epidermal cells of leaves of many species. Not much is known about the development of plastids in the epidermal tissue. Sunflower was selected to study the plastid development in the epidermal tissue.Sunflower plants were grown from seeds in growth chambers maintained on a 14:10 light:dark cycle at a daytime temperature of 78 F and nighttime temperature of 70 F with 80% humidity. Samples for ultrastructural study were taken from primary leaves at different stages of development. Because the rate of leaf development can vary from plant to plant, samples were taken from the same primary leaves of selected seedlings. These samples fixed in glutaraldehyde followed by osmium tetroxide were processed for electron microscopy using standard procedures.

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Developmental Effects on Relative Use of PEPCK and NADP-ME Pathways of C4 Photosynthesis in Maize

10.1101/2021.06.25.449949 ◽

2021 ◽

Author(s):

Jennifer J Arp ◽

Shrikaar Kambhampati ◽

Kevin Chu ◽

Somnath Koley ◽

Lauren M Jenkins ◽

...

Keyword(s):

Enzyme Activity ◽

Leaf Development ◽

Phosphoenolpyruvate Carboxykinase ◽

C4 Photosynthesis ◽

Leaf Age ◽

Bundle Sheath ◽

Decarboxylase Activity ◽

Mesophyll Cells ◽

Source To Sink ◽

Canopy Position

C4 photosynthesis is an adaptive photosynthetic pathway which concentrates CO2 around Rubisco in specialized bundle sheath cells to reduce photorespiration. Historically, the pathway has been characterized into three different subtypes based on the decarboxylase involved, although recent work has provided evidence that some plants can use multiple decarboxylases, with maize in particular using both the NADP-malic enzyme (NADP-ME) pathway and phosphoenolpyruvate carboxykinase (PEPCK) pathway. Parallel C4 pathways could be advantageous in balancing energy and reducing equivalents between bundle sheath and mesophyll cells, in decreasing the size of the metabolite gradients between cells and may better accommodate changing environmental conditions or source to sink demands on growth. The enzyme activity of C4 decarboxylases can fluctuate with different stages of leaf development, but it remains unclear if the pathway flexibility is an innate aspect of leaf development or an adaptation to the leaf microenvironment that is regulated by the plant. In this study, variation in the two C4 pathways in maize were characterized at nine plant ages throughout the life cycle. Two positions in the canopy were examined for variation in physiology, gene expression, metabolite concentration, and enzyme activity, with particular interest in asparagine as a potential regulator of C4 decarboxylase activity. Variation in C4 and C3 metabolism was observed for both leaf age and canopy position, reflecting the ability of C4 pathways to adapt to changing microenvironments.

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Gene Expression and Accumulation of Rubisco in Bundle Sheath and Mesophyll Cells during Leaf Development and Senescence in Rice, a C3 Plant

Plant Production Science ◽

10.1626/pps.11.336 ◽

2008 ◽

Vol 11 (3) ◽

pp. 336-343 ◽

Cited By ~ 8

Author(s):

Koichi Tsutsumi ◽

Michio Kawasaki ◽

Mitsutaka Taniguchi ◽

Hiroshi Miyake

Keyword(s):

Gene Expression ◽

Leaf Development ◽

Bundle Sheath ◽

Mesophyll Cells ◽

C3 Plant

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Chloroplast nucleoids are highly dynamic in ploidy, number, and structure during angiosperm leaf development

10.1101/632240 ◽

2019 ◽

Author(s):

Stephan Greiner ◽

Hieronim Golczyk ◽

Irina Malinova ◽

Tommaso Pellizzer ◽

Ralph Bock ◽

...

Keyword(s):

Leaf Development ◽

Plastid Dna ◽

Epifluorescence Microscopy ◽

Mesophyll Cells ◽

High Molecular Weight Dna ◽

Organelle Dna ◽

Plastid Genomes ◽

Chloroplast Nucleoids ◽

Pulsed Field Electrophoresis ◽

Multiple Copies

SummaryChloroplast nucleoids are large, compact nucleoprotein structures containing multiple copies of the plastid genome. Studies on structural and quantitative changes of plastid DNA (ptDNA) during leaf development are scarce and have produced controversial data. We have systematically investigated nucleoid dynamics and ptDNA quantities in mesophyll ofArabidopsis, tobacco, sugar beet, and maize from the early post-meristematic stage until necrosis. DNA of individual nucleoids was quantified by DAPI-based supersensitive epifluorescence microscopy. Nucleoids occurred in scattered, stacked or ring-shaped arrangements and in recurring patterns during leaf development remarkably similar between the species studied. Nucleoids per organelle varied from few in meristematic plastids to >30 in mature chloroplasts (corresponding to about 20-750 nucleoids per cell). Nucleoid ploidies ranged from haploid to >20-fold even within individual organelles, with average values between 2.6- and 6.7-fold and little changes during leaf development. DNA quantities per organelle increased gradually from about a dozen plastome copies in tiny plastids of apex cells to 70-130 copies in chloroplasts of about 7 μm diameter in mature mesophyll tissue, and from about 80 plastome copies in meristematic cells to 2,600-3,300 copies in mature diploid mesophyll cells without conspicuous decline during leaf development. Pulsed-field electrophoresis, restriction of high-molecular weight DNA from chloroplasts and gerontoplasts, and CsCl equilibrium centrifugation of single- and double-stranded ptDNA revealed no noticeable fragmentation of the organelle DNA during leaf development, implying that plastid genomes in mesophyll tissues are remarkably stable until senescence.Significance StatementPlastid DNA is organized in nucleoids that are highly dynamic in organization, structure and amount during leaf development. The present investigation fully resolves now this dynamic and is a precise cytogenetic characterization of nucleoids DNA spanning the entire life cycle of the leaf.

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The distribution of calcium and magnesium in developing tobacco leaves as measured by low-temperature X-ray microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100103607 ◽

1988 ◽

Vol 46 ◽

pp. 308-309

Author(s):

Patrick Echlin

Keyword(s):

Leaf Development ◽

Cell Types ◽

Tissue Level ◽

Lower Epidermis ◽

Calcium Oxalate Crystals ◽

Mesophyll Cells ◽

Spongy Mesophyll ◽

X Ray ◽

Stages Of Growth ◽

Calcium And Magnesium

The processes of leaf maturation and senescence are linked closely to the redirection of ions and organic nutrients between leaves and other part of the plant. It is known from work on whole leaves, that Ca2+ and Mg2+ play an important role in leaf development, although no studies have been made of changes at the cell and tissue level. This present study follows the cellular changes in Ca2+ and Mg2+ in the epidermal and photosynthetic tissues by X-ray microanalysis of frozen hydrated leaves.Full details of sample preparation, instrumentation, and the basis of the quantitative procedures have been reported elsewhere. Flat, frozen hydrated fracture faces of upper and lower epidermis; palisade and spongy mesophyll cells were analysed for Ca2+ and Mg2+. Data was collected from each of the four cell types in 20 different leaves at each of the following five stages of growth. Juvenile (10 weeks from seed); Mature (13 weeks), Ripe (16 weeks), Senescent (19 weeks) and Old (21 weeks). Cells containing obvious calcium oxalate crystals were avoided.

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Ultrastructure and Senescence in an Achloroplastic Mutant of Hordeum vulgare L. cv. Dyan

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100124628 ◽

1992 ◽

Vol 50 (1) ◽

pp. 844-845

Author(s):

R.H.M. Cross ◽

C.E.J. Botha ◽

A.K. Cowan ◽

B.J. Hartley

Keyword(s):

Cell Wall ◽

Hordeum Vulgare ◽

Leaf Tissue ◽

Ultrastructural Changes ◽

Hordeum Vulgare L ◽

Mesophyll Cells ◽

Lethal Mutant ◽

Cytoplasmic Matrix ◽

Close Proximity ◽

Pinocytotic Vesicles

Senescence is an ordered degenerative process leading to death of individual cells, organs and organisms. The detection of a conditional lethal mutant (achloroplastic) of Hordeum vulgare has enabled us to investigate ultrastructural changes occurring in leaf tissue during foliar senescence.Examination of the tonoplast structure in six and 14 day-old mutant tissue revealed a progressive degeneration and disappearance of the membrane, apparently starting by day six in the vicinity of the mitochondria associated with the degenerating proplastid (Fig. 1.) where neither of the plastid membrane leaflets is evident (arrows, Fig. 1.). At this stage there was evidence that the mitochondrial membranes were undergoing retrogressive changes, coupled with disorganization of cristae (Fig. 2.). Proplastids (P) lack definitive prolamellar bodies. The cytoplasmic matrix is largely agranular, with few endoplasmic reticulum (ER) cisternae or polyribosomal aggregates. Interestingly, large numbers of actively-budding dictysomes, associated with pinocytotic vesicles, were observed in close proximity to the plasmalemma of mesophyll cells (Fig. 3.). By day 14 however, mesophyll cells showed almost complete breakdown of subcellular organelle structure (Fig. 4.), and further evidence for the breakdown of the tonoplast. The final stage of senescence is characterized by the solubilization of the cell wall due to expression and activity of polygalacturonase and/or cellulose. The presence of dictyosomes with associated pinocytotic vesicles formed from the mature face, in close proximity to both the plasmalemma and the cell wall, would appear to support the model proposed by Christopherson for the secretion of cellulase. This pathway of synthesis is typical for secretory glycoproteins.

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Structural aspects of tracheary element differentiation in suspension cultures of Zinnia elegans

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100155815 ◽

1989 ◽

Vol 47 ◽

pp. 768-769

Author(s):

C. H. Haigler ◽

A. W. Roberts

Keyword(s):

Tracheary Element ◽

Vesicle Fusion ◽

Zinnia Elegans ◽

Cellulose Synthesis ◽

Tracheary Elements ◽

Animal Cells ◽

Mesophyll Cells ◽

Fixation Techniques ◽

Localized Patterns ◽

Structural Aspects

Tracheary elements, the water-conducting cells in plants, are characterized by their reinforced walls that became thickened in localized patterns during differentiation (Fig. 1). The synthesis of this localized wall involves abundant secretion of Golgi vesicles that export preformed matrix polysaccharides and putative proteins involved in cellulose synthesis. Since the cells are not growing, some kind of endocytotic process must also occur. Many researchers have commented on where exocytosis occurs in relation to the thickenings (for example, see), but they based their interpretations on chemical fixation techniques that are not likely to provide reliable information about rapid processes such as vesicle fusion. We have used rapid freezing to more accurately assess patterns of vesicle fusion in tracheary elements. We have also determined the localization of calcium, which is known to regulate vesicle fusion in plant and animal cells.Mesophyll cells were obtained from immature first leaves of Zinnia elegans var. Envy (Park Seed Co., Greenwood, S.C.) and cultured as described previously with the following exceptions: (a) concentration of benzylaminopurine in the culture medium was reduced to 0.2 mg/l and myoinositol was eliminated; and (b) 1.75ml cultures were incubated in 22 x 90mm shell vials with 112rpm rotary shaking. Cells that were actively involved in differentiation were harvested and frozen in solidifying Freon as described previously. Fractures occurred preferentially at the cell/planchet interface, which allowed us to find some excellently-preserved cells in the replicas. Other differentiating cells were incubated for 20-30 min in 10(μM CTC (Sigma), an antibiotic that fluoresces in the presence of membrane-sequestered calcium. They were observed in an Olympus BH-2 microscope equipped for epi-fluorescence (violet filter package and additional Zeiss KP560 barrier filter to block chlorophyll autofluorescence).

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