Nicotiana, chloroplast

Herrera-Estrella, L., Van den Broek, G., Maenhault, R., Van Montagu, M., Schell, J., Timko, M. Cashmore, A. (1985). Light-inducible and chloroplast-associated expression of a chimaeric gene introduced into Nicotiana tabacum using a Ti plasmic vector. Nature, 310,115-20. 

Reserve starch is usually formed in amyloplasts, although it is occasionally formed in chloroamyloplasts. These are chloroplasts that have lost their lamellar structure and subsequently start producing fairly large reserve starch granules.17 Chloroamyloplasts form starch independent of photosynthesis. They have been described in tobacco (Nicotiana tabacum L.) leaves, Aloe leaves and flowers, central pith of potato (Solanum tuberosum L.) fruit, Pellionia and Dieffenbachia stems, and other tissues.17,18 Such sources of reserve starch are insignificant, however, when compared to the reserve starch formed in roots, tubers and seeds. 

A chloroplast location of the gene for Cyt / was suggested by two plastome mutants of Oenothera which were deficient in spectrally detected Cyt/[102], and by the maternal mode of inheritance of Cyt /in interspecific Fj hybrids of Nicotiana [103]. The structural gene (petA) for the Cyt / polypeptide was initially localized and characterized from pea chloroplast DNA [104,105], and subsequently from wheat [106], spinach [107] and Oenothera [108]. Open reading frames of 320 codons have been detected in chloroplast DNA from each of these plants. Comparison with the determined N-terminal sequence of Cyt / indicates the presence of a 35 amino acid residue pre-sequence and a mature polypeptide of 285 amino acid residues. A putative haem-binding site, Cys-Ala-Asn-Cys-His, is located near the... 

Preparation of Thylakoid Vesicles. Broken (class C) chloroplasts from peas (Pisum sativum) and tobacco (Nicotiana tobacum) were prepared according to the method of Avron (29). The chloroplasts were resuspended in a medium containing 0.4-M sucrose and 10-mM tris(hydroxymethyl)aminomethane (Tris pH 7.5), and stored at liquid nitrogen temperature in the same medium supplementated with 30% v/v of ethylene glycol (30). The chloroplasts (6-mg/mL chlorophyl) were heat inactivated for 3 min 51 °C and then diluted by 1 500 with a double-distilled water that was adjusted to pH 7.7 with Tris buffer. Large thylakoid vesicles were formed due to the swelling process under these hypotonic conditions. The size distribution of the thylakoid vesicles was determined as previously described (18). 

Beisenherz, W.V. and P. Koth Influence of chloramphenicol and cycloheximide on the synthesis of ribnlose-l,5-diphosphate-carboxlase, glycerinaldehyde-3-phosphate-dehydrogenase, and chlorophyll during lencoplast-chloroplast-tranformation in tissue cultures of Nicotiana tabacum-, Z. Pflanzenphysiol. 75 (1974) 201-210. 

Haise, K.P. and G. Jacobi Comparative smdies on the lipid composition of etioplasts and chloroplasts from fisum and of chloroplasts from a mutant Nicotiana, Planta 111 (1973) 137-148. 

Protoplast fusion provides ein alternative method for chloroplast transfer (17,18). Transfer is based on the independent segregation of chloroplasts eind nuclei in heterokaryons obtained by protoplast fusion. Efficiency of recovery for specific combinations of chloroplasts and nuclei has been facilitated by using selectable chloroplast markers such as streptomycin or linoomyoin resistance, or by using maternal pigment-deficient mutants to visually differentiate between clones carrying donor and recipient chloroplasts. Elimination of the nucleus of the chloroplast donor is facilitated by irradiation of donor protoplasts prior to fusion. Methods of chloroplast transfer by protoplast fusion have been reviewed (17,18). In this review only transfer of triazine-resistant chloroplasts will be covered. Work in Nicotiana is more recent than in rapeseed ( 9) and potato (, 1 ), but serves to Illustrate the methodology of chloroplast transfer by protoplast fusion. 

Approximately 5 000 naturally abundant acyclic and cyclic diterpenes derived from the parent hydrocarbon phytane are known The (3i ,7i ,ll )-enantiomer of phy-tane has been found in meteorites, oil slate, other sediments and, last but not least, in human liver. Oil slate additionally eontains (-)-(3if,7if,llif)-phytanoic acid which has also been isolated from butter. 1,3(20)-Phytadiene is one among many constituents of tobacco Nicotiana tabacum (Solanaceae) -1,3-phytadiene and its (%)-isomer are found in zooplankton. Chlorophyll in the chloroplasts of plant cells exemplifies an ester of +)-(lE,lR, l/ )-2-phyten-l-ol usually referred to as phytol. 2,6,10,14-Phytatetraene-l,19-diol, better known as plaunotol, is the ehief constituent of the leaves of flie Thai medicinal plant Croton sublyratus (Euphorbiaceae) used as "plau noi" or "kelnac" as an antiulcerative. 

We have examined two complete chloroplast genome sequences (Nicotiana tabacum (12) and Marchantia polymorpha (13)) and some individual chloroplast genes searching for LRE-like matrices homologous to the light responsive elements found in plant nuclear light-inducible... 

For the first step of the analysis of PSI biogenesis, we determined which subunits of PSI are nuclear-encoded. PSI complex was prepared from several species of Nicotiana, and each subunit was separated by high resolution LDS PAGE. Partial amino acid sequences were determined for each subunit, and compared with the amino acid sequences deduced from tobacco chloroplast DNA sequence in order to determine which subunits are chloroplast-encoded. As far as the PSI subunits having mol. wt. from 5.6 kDa to 20 kDa are concerned, it was only psaC protein that was proved to be of chloroplast origin. All the others, some of which are blocked at their N termini, are not coded for by chloroplast DNA, indicating that they are of nuclear origin. 

Another aspect of the diversity is the heterogeneity of the subunit encoded by the haploid genome. It is well known that the apoproteins of LHCP are coded for by the multigene family, manifesting multiformity. As for the PSI complex, we found the evidence that the haploid genome of Nicotiana codes for two types of psaD proteins (Obokata et al. in preparation). Since the chloroplast genome does not code for a multigene family as far as we know, this type of diversity is also a characteristic of the nuclear-encoded subunits. 

Various pathotypes also produce a cyclic tetrapep-tide known as tentoxin (Fig. 2) which induces chlorosis in many plants (e.g. lettuce, potato, cucumber, spinach), but not in Nicotiana, tomato, cabbage or radish. It binds to chloroplast coupling factor 1 (one toxin-binding site per aP subunit complex), inhibiting photophosphorylation and the Ca -dependent ATP-ase. Species specificity is due to different binding affinities for coupling factor 1 (1.3-20 x lO M for 50% inhibition in sensitive species, and 20-fold higher for insensitive species). 

Present in leaves and chloroplasts of Antirrhinum majus, in Nicotiana sp. and in cuticular membranes of insect spp. 

Kung SD, Zhu YS, Chen K (1982) Nicotiana cWoroplast genome III. Chloroplast DNA evolution. Theor Appl Genet 61 73-79... 

Serological studies have shown that the lipid distribution in the lamellar system of chloroplasts shows a lateral and transversal asymmetry (Radunz, 1980). We have analysed the lipid composition of chloroplasts from the variegated tobacco mutant Nicotiana tabacum NC 95. 

Table 1 Per Cent of Lipids Referred to the Total Lipid Content of Chloroplasts from Green (Chl ) and Yellow-Green (Chly ) Leaf Areas and of Photosystem II Particles (PS II), Reaction Center Complexes (RCC) and Light-Harvesting Complexes (LHC) from Green Leaf Areas of the Tobacco Mutant Nicotiana tabacum NC 95... 

Nicotiana tabacum var. Xanthi with the lipid composition of chloroplasts of N. 

Although only limited results are currently available, enzymes associated with amino acid biosynthesis in higher plants appear to be nuclear encoded. Consequently, transport into chloroplasts would be expected to be facilitated by the presence of an N-terminal transit peptide on the initial translation product. This appears to be the case with acetolactate synthase (19), which is nuclear encoded and localized in chloroplasts (Chaleff and Ray, 1984). Evidence for nucleotide sequences that could code for an N-terminal transit peptide composed of between 85 and 99 residues was obtained for the genes isolated from Arabidopsis and Nicotiana (Mazur et al, 1987). The absence of synthesis of iS-adenosylmethionine in plastids is further supported by the apparent lack of a nucleotide sequence coding for a transit peptide in an adenylatetransferase Arabidopsis gene (Peleman et al., 1989). 

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