Mitochondria vacuolation

The rate of photosynthesis does not depend on the amount of a single component (e.g., the activity of a particular enzyme). There is a wide range of possible regulatory factors, proven to exist in vitro, but the importance of which in vivo has still to be determined. In particular, there is a multitude of factors affecting the activity of the enzymes involved, with pH, ions, coenzymes, and metabolite effectors modulating the activity of every enzyme studied thus far. Compartmentation is the other key factor. The role of metabolite transport in the cell, particularly between chloroplast and cytosol, but also to and from mitochondria, vacuole, and other organelles, is now considered to be fundamental to the regulation of photosynthesis. In this chapter, we look at the factors considered to be of major importance... 

Organelles—a differentiated structure within a cell, such as a mitochondrion, vacuole, or chloroplast that performs a specific function. 

Fig. 2.6 The moqjhological events of sporulation in Saccharomyces cerevisiae. (a) starved cell V, vacuole LG, lipid granule ER, endoplasmic reticulum CW, cell wall M, mitochondrion S, spindle pole SM, spindle microtubules N, nucleus NO, nucleolus, (b) Synaptonemal complex (SX) and development of polycomplex body (PB) along with division of spindle pole body in (c). (d) First meiotic division which is completed in (e). (f) Prepararation for meiosis II. (g) Enlargement of prospore wall, culminating in enclosure of separate haploid nuclei (h). (i) Spore coat (SC) materials produced and deposited, giving rise to the distinct outer spore coat (OSC) seen in the completed spores of the mature ascus (j). Reproduced from the review by Dickinson (1988) with permission from Blackwell Science Ltd.

Fig. 7.5. A schematic indication of some of the different membrane separated compartments in an advanced cell. PEROX is a peroxisome MITOCHLORO is either a mitochondrion or a chloroplast CHROMO is a vesicle of, say, the chromaffin granule ENDO is a reticulum, e.g. the endoplasmic reticulum. Other compartments are lysosomes, vacuoles, calcisomes and so on. Localised metal concentrations are shown. The figure is of a transverse section. To appreciate a cell fully it is necessary to have serial plane sections in parallel along the. "-direction.

In spite of the variety of appearances of eukaryotic cells, their intracellular structures are essentially the same. Because of their extensive internal membrane structure, however, the problem of precise protein sorting for eukaryotic cells becomes much more difficult than that for bacteria. Figure 4 schematically illustrates this situation. There are various membrane-bound compartments within the cell. Such compartments are called organelles. Besides the plasma membrane, a typical animal cell has the nucleus, the mitochondrion (which has two membranes see Fig. 6), the peroxisome, the ER, the Golgi apparatus, the lysosome, and the endosome, among others. As for the Golgi apparatus, there are more precise distinctions between the cis, medial, and trans cisternae, and the TGN trans Golgi network) (see Fig. 8). In typical plant cells, the chloroplast (which has three membranes see Fig. 7) and the cell wall are added, and the lysosome is replaced with the vacuole. 

A variety of protein import pathways into the vacuole are known (Burd et al., 1998 Bryant and Stevens, 1998). It includes the sorting from the Golgi apparatus, endocytosis, autophagy (where a part of the cytoplasm such as a mitochondrion is engulfed into a newly formed vacuole and is degraded), direct import from the cytosol, and the vacuolar inheritance from the mother cell. Of these, the pathways from the Golgi... 

The cell organellae in woody plants are the nucleus, mitochondrion, rough-endoplasmic reticulum (r-ER), smooth endoplasmic reticulum (s-ER), Golgi-body, plastid, vacuole, microbody, etc. Their functions are very complicated, and some have definite roles in the biosynthesis of cell-wall components. Hence, changes in size of cell organellae are likely to occur, since cell-wall composition depends upon the stage of wall development. 

Electron microscopy of radish radicle. Details of roots from seeds treated with 1/14-diluted reverse osmosis fraction, (a) Cortical cells showing protein-body-derived vacuoles (V) with remnants of electron-opaque protein material. Extremely swollen mitochondria (M) look like vacuoles with fine granular contents, (b) Detail of epidermal cell, showing swollen mitochondria (M), lipid droplets (L) and two dictyosomes (D). (c) The area enclosed in the rectangle in (b) is enlarged to show the two-membrane envelope and residual cristae (arrows) in a swollen mitochondrion. 

Figure 1. a. Section of untreated control cell of S. cerevisiae. b. Section of S. cerevisiae cell treated with 50 /xg/ml of polygodial for 10 min. CW, cell wall PM, plasma membrane (cell membrane) N, nucleus M, mitochondrion V, vacuole. 

Abbreviations NBD, nucleotide binding domain TMS, transmembrane-spanning segment NTE, N-terminal extension PDR, pleiotropic drug resistance PM, plasma membrane V, vacuole M, mitochondrion P, peroxisome C, cytoplasm LCFA, long chain fatty acid EF, elongation factor. 

Fig. 16.2 Diagram of an electron micrograph of a section through a resting cell of bakers yeast Saccharomyces certvisiae). ER, endoplasmic reticulum M, mitochondrion N, nucleus Nm, nuclear membrane Nn, nucleolus Pi, invagination PI, plasmalemma V, vacuole Vp, polymetaphosphate granule W, cell wall Ws, bud scar L, lipid granule (sphaerosome).

Fig. 3.18. Cell of a hypothetical oil seed producing storage proteins and sequestering them within a vacuole. P polyribosomes, D dictyosome, V storage vacuole, M mitochondrion, CW cell wall, GV membrane-bound vesicles. L plastid, S oil body, PD plasmodesma N nucleus, Nu nucleolus, ER endoplasmic reticulum. Kindly provided by J.C. and M.W. Dieckert. See also Dieckert and Dieckert, 1972 [5] scheme devised from electron micrographs presented in this paper...

The presented data, taken from two large alkaloid families, demonstrate that most plant organelles can harbor elements of alkaloid biosynthesis, i.e. cytosol, ER membranes, ER-derived vesicles, vacuoles, provacuolar vesicles and chloroplasts. In rare cases, even an actively metabolizing organell as the mitochondrion can be involved in alkaloid biosynthesis the lysine-derived quinolizidine alkaloids epilu-pinine and multiflorine are synthesized in the chloroplasts of mesophyll cells in several legumes. The finalizing step is an acylation of these molecules, which occurs in the cytoplasm. 

Figure 1. (A). A diagrammatic representation of a plant cell. The cytoplasm is bounded by the plasma membrane which is itself surrounded by the primary wall. The region where the primary walls of two cells abut one another is called the middle lamella. Air spaces are often present particularly at the junction of cell comers. Abbreviations used—Pla = plastid Chi = chloroplast Mit = mitochondrion Nuc = nucleus Vac = vacuole Cyt = cytoplasm Pdm = plasmodesmata. (B). A simplified model of a possible arrangement of the major wall components. Wall proteins have been omitted for clarity. Abbreviations used HG = homogalacturonan RG-I = rhamnogalacturonan I RG-II = rhamnogalacturonan II B-ester = borate ester cross-link of RG-II XG xyloglucan...

Fig. 1. Section through the center of the lower part of a chloroplast in a C. reinhardi y-1 cell, grown in the light. The chloroplast envelope (ce) surrounds the matrix occupied by numerous grana sectioned perpendicularly (g) or tangentially (gi). Some of the thylakoids interconnect different grana (T). Osmiophyllic globules (os) and ribosomes (r) are found in the stroma. A pyrenoid (py) surrounded by starch plates (s) occupies the center of the chloroplast. N, nucleus n, nucleolus V, vacuole cr, cytoplasmic ribosomes d, dicytisome p, plasma membrane m, mitochondrion cw, cell wall. (24,500x)...

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