Of chloroplasts

Light and photosynthetic electron transport convert DPEs into free radicals of undetermined stmcture. The radicals produced in the presence of the bipyridinium and DPE herbicides decrease leaf chlorophyll and carotenoid content and initiate general destmction of chloroplasts with concomitant formation of short-chain hydrocarbons from polyunsaturated fatty acids (37,97). 

FIGURE 22.27 Light-induced pH changes in chloroplast compartments. Illumination of chloroplasts leads to proton pumping and pH changes in the chloroplast, such that the pH within the thylakoid space falls and the pH of the stroma rises. These pH changes modulate the activity of key Calvin cycle enzymes. 

As discussed in Section 22.7, illumination of chloroplasts leads to light-driven pumping of protons into the thylakoid lumen, which causes pH changes in both the stroma and the thylakoid lumen (Figure 22.27). The stromal pH rises, typically to pH 8. Because rubisco and rubisco activase are more active at pH 8, COg fixation is activated as stromal pH rises. Fructose-1,6-bisphosphatase, ribulose-5-phosphate kinase, and glyceraldehyde-3-phosphate dehydrogenase all have alkaline pH optima. Thus, their activities increase as a result of the light-induced pH increase in the stroma. 

Knaff, D. B., 1991. Regnlatory phosphoryladon of chloroplast antenna proteins. Trends in Biochemical Sciences 16 82-83. Additional discussion of the structure of light-harvesdng antenna complexes associated widi photo-synthedc reaction centers can be found in Trends in Biochemical Sciences 11 414 (1986), 14 72 (1989), and 16 181 (1991). 

Steponkus, P.L., Garber, M.P., Myers, S.P., Lineberger, R.D. (1977). Effects ofcold acclimation and freezing on structure and function of chloroplast thylakoids, Cryobiol. 14, 303-321. 

In be complexes bci complexes of mitochondria and bacteria and b f complexes of chloroplasts), the catalytic domain of the Rieske protein corresponding to the isolated water-soluble fragments that have been crystallized is anchored to the rest of the complex (in particular, cytochrome b) by a long (37 residues in bovine heart bci complex) transmembrane helix acting as a membrane anchor (41, 42). The great length of the transmembrane helix is due to the fact that the helix stretches across the bci complex dimer and that the catalytic domain of the Rieske protein is swapped between the monomers, that is, the transmembrane helix interacts with one monomer and the catalytic domain with the other monomer. The connection between the membrane anchor and the catalytic domain is formed by a 12-residue flexible linker that allows for movement of the catalytic domain during the turnover of the enzyme (Fig. 8a see Section VII). Three different positional states of the catalytic domain of the Rieske protein have been observed in different crystal forms (Fig. 8b) (41, 42) ... 

Krause, G.H. Behrend, U. (1986). A pH-dependent chlorophyll fluorescence quenching indicating a mechanism of protection against photoinhibition of chloroplasts. FEBS Letters, 200, 298-302. 

Trebst, A. (1974). Energy conservation in photosynthetie electron transport of chloroplasts. Annual Review of Plant Physiology, 25, 423-58. 

Sytsma, K. J., Smith, J. F. and Berry, P. E. 1991. The use of chloroplast DNA to assess biogeography and evolution of morphology, breeding systems, and flavonoids in Fuchsia sect. Skin-nera (Onagraceae). Syst. Bot. 16 257-269. 

Over-expression of bacterial phytoene synthase led to only modest increases in pigment accumulation (except in the case of chloroplast-contaiifing tissues). Attention turned to CrtI, one gene that might control flux through the entire four desaturation steps from phytoene to lycopene (discussed in Section 5.3.2.4). Only a modest increase in carotenoid content in tomatoes and a variety of changes in carotenoid composition including more P-carotene, accompanied by an overall decrease in total carotenoid content (no lycopene increase), resulted when CrtI was over-expressed under control of CaMV 35S. Apparently, the bacterial desaturase... 

Plant DNA Allergen checker [Plant] Oriental Yeast Co., Ltd. Noncoding region of chloroplast DNA Approximately 124... 

It has been suggested that trapping of this delocalized excitation by low-energy impurity molecules could play an important role in the photophysics of chloroplasts. After trapping the excitation energy, it could be transferred to a reactant or an electron transfer reaction could occur/351... 

Horton P., Ruban, A.V., Rees D., A. Pascal, Noctor, G.D., and Young, A.J. 1991. Control of the light-harvesting function of chloroplast membranes by the proton concentration in the thylakoid lumen aggregation states of the LHCII complex and the role of zeaxanthin. FEBS Lett. 292 1-4. 

Horton, P., Wentworth, M., and Ruban, A. 2005. Control of the light harvesting function of chloroplast membranes The LHCII-aggregation model for non-photochemical quenching II. FEBS Lett. 579 4201 1206. 

According to the endosymbiotic hypothesis, the eukaryotes used genes from both bacteria (alpha-protobacteria) and cyanobacteria. The first led to the development of mitochondria, the second to that of chloroplasts, i.e., cell organelles which are highly important for energy production (ATP synthesis) and photosynthesis. 

Some organisms, notably parasites, have organelles , which appear to be relics of chloroplasts but have no photosynthetic capacity. They are called apicoplasts but are probably not the origin of chloroplasts. Also note that a feature of symbiosis is that genes that are no longer required can be selectively lost as was probably the case in the example of loss from bacteria on becoming mitochondria (mentioned above). 

Those striking bluelight-induced morphological responses such as phototropism, induction of polarity of spores or rearrangement of chloroplasts, are necessarily preceded by metabolic bluelight effects. However, no clear-cut causal reaction chain has yet been elucidated. 

Fig. 17. Rearrangement of chloroplasts in the upper epidermis of Selaginella as induced by polarized left, bright light (3.5 104 erg/cm2 s) right, weak light (400 erg/cm2 s)114)...

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