Effects of Nutritional Levels of Phosphate on Photosynthesis and Growth Studied with Single, Rooted Leaf of Dwarf Bean

When a single, rooted leaf of dwarf bean (Phaseolus vulgaris,var. humilis Edogawa) was grown in a phosphate-deficient conditionin light, expansion of the leaf stopped earlier than the increasein the volume of the root. These results indicate that the useof the assimilate for leaf expansion stops early in comparisonto the transport of the assimilate to the roots, when the externalsupply of phosphate is discontinued. After transfer to the phosphate-deficientcondition, the photosynthetic capacity increased for severaldays, then decreased. On the 12th day after transfer, the photosyntheticcapacity reached its lowest level. When phosphate was addedto the roots at an early stage of phosphorus deficiency, photosynthesisshowed little recovery during the first 3 hr alter the addition,but it recovered largely between 3 and 48 hr. But, at a laterdeficient stage, it was restored largely during the first 3hr, as well as being maintained between 3 and 48 hr. This immediaterecovery of photosynthesis within 3 hr after the addition ofphosphate increased largely in spite of decreasing photosynthesisin the plants subjected to progressive phosphorus-deficientstress. (Received April 2, 1981; Accepted October 23, 1981)     

Molecular structure, localization and function of biliproteins in the chlorophyll a/d containing oxygenic photosynthetic prokaryote Acaryochloris marina.

We investigated the localization, structure and function of the biliproteins of the oxygenic photosynthetic prokaryote Acaryochloris marina, the sole organism known to date that contains chlorophyll d as the predominant photosynthetic pigment. The biliproteins were isolated by means of sucrose gradient centrifugation, ion exchange and gel filtration chromatography. Up to six biliprotein subunits in a molecular mass range of 15.5-18.4 kDa were found that cross-reacted with antibodies raised against phycocyanin or allophycocyanin from a red alga. N-Terminal sequences of the alpha- and beta-subunits of phycocyanin showed high homogeneity to those of cyanobacteria and red algae, but not to those of cryptomonads. As shown by electron microscopy, the native biliprotein aggregates are organized as rod-shaped structures and located on the cytoplasmic side of the thylakoid membranes predominantly in unstacked thylakoid regions. Biochemical and spectroscopic analysis revealed that they consist of four hexameric units, some of which are composed of phycocyanin alone, others of phycocyanin together with allophycocyanin. Spectroscopic analysis of isolated photosynthetic reaction center complexes demonstrated that the biliproteins are physically attached to the photosystem II complexes, transferring light energy to the photosystem II reaction center chlorophyll d with high efficiency.     

Changes of Starch Localization within the Chloroplast Induced by Changes in CO2 Concentration during Growth of Chlamydomonas reinhardtii: Independent Regulation of Pyrenoid Starch and Stroma Starch

To understand the physiological function of the pyrenoid, aprotein complex in algal chloroplast stroma with surroundingstarch sheaths, the effects of environmental conditions on thepyrenoid and pyrenoid starch were investigated in the unicellulargreen alga Chlamydomonas reinhardtii. Pyrenoid starch was rapidlyaccumulated within 5 hours when the extracellular CO₂ concentrationwas lowered from 4% to ordinary air level (0.04%). Startingwith high-CO₂ grown cells containing well-developed stroma starchgranules, degradation of stroma starch and accumulation of pyrenoidstarch were observed in parallel during the adaptation to lowCO₂ condition. This pyrenoid-starch accumulation was light dependentand completely inhibited by DCMU. The starch relocalizationprocess was reversible, but the breakdown of pyrenoid starchwas slower than its accumulation. The time courses of accumulation(or degradation) of starch around the pyrenoid paralleled increases(or decreases) in carbonic anhydrase (EC 4.2.1.1 [EC] ) activity,and the pyrenoid starch accumulation is thought to be one ofthe adaptation phenomena to CO₂ concentration. When nitrogenassimilation was inhibited, stroma starch and total starch contentincreased, while that of pyrenoid starch decreased. These resultsindicate that the synthesis and degradation of the two formsof starch were regulated independently by the environmentalconditions. ADP-glucose starch synthase (EC 2.4.1.21 [EC] ) activitywas detected at a physiological level, but the change of starchlocalization could not be explained by total starch synthaseactivity nor by starch-degrading enzyme activities. We assumethat starch metabolism around the pyrenoid is regulated independentlyfrom that in other stromal spaces. (Received May 16, 1988; Accepted July 17, 1988)     

Effects of glutathione depletion on the synthesis of proteoglycan and collagen in cultured chondrocytes

We studied the effect of the depletion of glutathione on the synthesis of proteoglycan and collagen in cultured chick chondrocytes. When the cultured chondrocytes were incubated with 1 mM buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamyl-cysteine synthetase, the intracellular glutathione level markedly dropped within 12 h with no loss of cell viability. Incorporation of 35SO2-4 into proteoglycan was lowered in the presence of BSO. When the 35S-labeled proteoglycans were separated into two fractions by glycerol density gradient centrifugation, the inhibitory effect of BSO on the synthesis of proteoglycan was greater in the fast-sedimenting proteoglycan fraction, which consisted mainly of cartilage specific large proteoglycan (PG-H), than in the slowly sedimenting proteoglycan fraction. The inhibition by BSO of the synthesis of core protein-free glycosaminoglycan chains primed by p-nitrophenyl-beta-D-xyloside was smaller than the inhibition of the synthesis of proteoglycan. Analysis of glycosaminoglycans labeled with [3H]glucosamine indicated that the treatment of chondrocytes with BSO resulted in a small increase in the proportion of synthesis of hyaluronic acid to the synthesis of total glycosaminoglycan. The incorporation of [3H]proline into collagen was also inhibited by BSO. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the 3H-labeled collagen showed that, in the presence of BSO, processing of Type II collagen appeared to slow down and the proportion of Type X collagen synthesis was reduced.     

Fatty acid composition of a new marine picoplankton species of the Chromophyta

A marine yellowish picoplankton, strain PP301, which was newly isolated from the surface seawater of the western Pacific Ocean was an eminent producer of polyunsaturated fatty acids. Its fatty acids were mostly shared by the shortest saturated form (14:0, 20–30%) and polyunsaturated forms (20:4, EPA and DHA) which accounted for about 50% of the total fatty acids. The amount of intermediate forms in 16 and 18 carbon chains were very little. This composition was consistently observed irrespective of the growth temperatures (15–35 °C).     

Assimilation of carbon dioxide in mesophyll chloroplasts and bundle sheath strands mechanically isolated from corn leaves

Mesophyll chloroplasts capable of assimilating 1.2 µmolesCO₂ per milligram chlorophyll per hour were isolated from 7-day-oldcorn (Zea mays, Nagano No. 1) leaves. Addition of phosphoenolpyruvateincreased the rate of CO₂ fixation in light up to 22 µmolesper milligram chlorophyll per hour, whole exogenously addedribose 5-phosphate and adenosine triphosphate brought aboutonly small increases. The CO₂ fixation products were mostlymalate and aspartate. Bundle sheath strands isolated from the same plants were capableof assimilating 3–26 µmoles CO₂ per milligram chlorophyllper hour. The fixation rate increased 3- to 5-fold on additionof ribose 5-phosphate and adenosine triphosphate, while exogenousphosphoenolpyruvate had no effect. The bulk of early productsof light-induced CO₂ fixation were phosphate esters. These results indicate that corn mesophyll chloroplasts initiallyfix CO₂ by phoenolpyruvate carboxylase and that reductive pentosephosphate cycle occurs in corn bundle sheath cells, but notin the mesophyll chloroplasts. (Received January 25, 1974; )     

Transport and Fixation of Inorganic Carbon during Photosynthesis in the Cells of Anabaena Grown under Ordinary Air. II. Effect of Sodium Concentration during Growth on the Induction of Active Trasport System for IC

The requirement of sodium for growth of Anabaena variabilisM3 was investigated under low (0.04%) and high (1.5 or 5%) CO₂conditions. The growth rates under both conditions were stronglyaffected by NaCl concentrations up to 0.5 mM in the medium.In the presence of 40 µM NaCl, the cells were not ableto grow under a low CO₂ condition, but were able to grow undera high CO₂ condition. The sodium requirement for growth wasdependent on pH: in the Na⁺-deficient condition, cells couldgrow at pH6.8, while no growth occurred at pH 8.2, suggestingthat the requirement of Na⁺ for growth observed in the low CO₂condition can be substituted for by a lower pH. In the presence of 20 mM NaCl at pH 7.8, ¹⁴CO₂ as well as H¹⁴CO₃^–were actively transported into the cells which had been grownin air. In contrast, the transport of both of these inorganiccarbon (IC) species was suppressed under the Na⁺-deficient condition.These results suggest that sodium is required for the stimulationof transport of IC during photosynthesis. This is one of thereasons why Na⁺ is required for the growth of Anabaena underordinary air and alkaline conditions. (Received September 27, 1986; Accepted March 26, 1987)     

Effect of Ammonia on Cellular pH of Anabaena cylindrica Determined with 31P NMR Spectroscopy

The pH changes in the blue-green alga (cyanobacterium) Anabaenacylindrica caused by addition of ammonia were investigated using³¹P NMR spectroscopy. A pH shift of 0.9 or more was observedwhen 30 nM NH₄OH was added to the cell suspension, but no significantcellular pH change was observed with 50 mM NH₄CI, a concentrationhigh enough to stimulate dark CO₂ fixation of this alga. Thechange in cellular pH does not seem to cause ammonia-inducedstimulation of dark CO₂ fixation. (Received June 22, 1985; Accepted January 10, 1986)