Molecular Detection of Epiphytic Acaryochloris spp. on Marine Macroalgae

A molecular method for detecting the epiphyte community on marine macroalgae was developed by using PCR-denaturing gradient gel electrophoresis. Selective amplification of 16S rRNA gene fragments from either cyanobacteria or algal plastids improved the detection of minor epiphytes. Two phylotypes of Acaryochloris, a chlorophyll d-containing cyanobacterium, were found not only on red macroalgae but also on green and brown macroalgae.     

Gonadotropin-releasing hormone increases melatonin release in the pineal gland of the female rat in vitro.

To evaluate the effect of gonadotropin-releasing hormone (GnRH) on melatonin ( N-acetyl-5-methoxytryptamine) release and its synthesizing enzyme activities in pineal glands, pineals from adult female rats during diestrus were organ-cultured in a medium containing 10 -12, 10 -10, or 10 -8 M GnRH for 6 h. Melatonin release increased significantly in pineals cultured with 10 -10 and 10 -8 M GnRH compared to controls. However, in pineal glands that were organ-cultured in a medium containing 10 -12 to 10 -8 M GnRH, the activity of arylalkylamine N-acetyltransferase, which is the key regulatory enzyme in melatonin biosynthesis, showed no significant difference from controls. Likewise, GnRH at these concentrations had no significant effect on the activity of pineal hydroxyindole- O-methyltransferase, which catalyzes the final step of melatonin biosynthesis. These results show that GnRH stimulates pineal melatonin release, but suggest that GnRH does not affect its melatonin synthesis.     

Allophycocyanin complexes of the phycobilisome from Mastigocladus laminosus. Influence of the linker polypeptide L8.9C on the spectral properties of the phycobiliprotein subunits

The following phycobiliproteins and complexes of the allophycocyanin core were isolated from phycobilisomes of the thermophilic cyanobacterium Mastigocladus laminosus: alpha AP, beta AP, (alpha AP beta AP), (alpha AP beta AP)3, (alpha AP beta AP)3L8.9C, (alpha APB alpha AP2 beta AP3)L8.9C. The six proteins and complexes were characterised spectroscopically with respect to absorption, oscillator strength, extinction coefficient, fluorescence emission, relative quantum yield, fluorescence emission polarisation and fluorescence excitation polarisation. The interpretation of the spectral data was based on the three-dimensional structure model of (alpha PC beta PC)3 (Schirmer et al. (1985) J. Mol. Biol. 184, 257-277), which is related to the allophycocyanin trimer. The absorption and CD spectra of the complexes (alpha AP beta AP)3, (alpha AP beta AP)3L8.9C and (alpha APB alpha AP2 beta AP3)L8.9C could be deconvoluted into the spectra of the phycobiliprotein subunits. The assumptions made for the deconvolution could be checked by the synthesis of the spectra of (alpha APB beta AP)3. The synthesised spectra are in good agreement with the corresponding measured spectra published by other authors. Considering the deconvoluted spectra the following influences on the chromophores could be ascribed to L8.9C: L8.9C neither influences the alpha AP nor the alpha APB chromophores. L8.9C shifts the absorption maximum of the beta AP chromophore to longer wavelength than the absorption maximum of the alpha AP chromophore in trimeric complexes. L8.9C increases the oszillator strength of the beta AP chromophores to about the value of the alpha AP chromophores in trimeric complexes. L8.9C turns the beta AP chromophores from sensitizing into weak fluorescing chromophores. By means of the hydropathy plot and the predicted secondary structure, a postulated three-fold symmetry in the tertiary structure of L8.9C could be confirmed.     

Identification of the Terminal Energy Donor to the Reaction Center in the Pigment System of Green Plants by Time-Resolved Fluorescence Spectroscopy at - 196C

A specific antenna component in the photosynthetic pigment system,the direct energy donor to the reaction center (RC), was identifiedin PS I and II in green plants by time-resolved fluorescencespectroscopy at – 196C. The fluorescence components weredetected at 707 nm and 685 nm for PS I and II, respectively,and these antennae are hereafter referred to as the terminalenergy donors. In PS II, component that fluoresces at 695 nmalso functions as an energy pool; its rise time is slow (50ps), suggesting that it represents a side path in the flow ofenergy. The energy levels of these direct donors were lowerthan, or almost the same as that of the primary electron donorsin RC I (P700) and II (P680), respectively. The similaritiesand differences between these donors are discussed in relationto the structural and energetic properties of the antenna componentsin PS I and II core complexes. ¹This paper is dedicated to Prof. Y. Fujita on the occationof the 60th anniversary of his birth.     

Establishment of the forward genetic analysis of the chlorophyll d-dominated cyanobacterium Acaryochloris marina MBIC 11017 by applying in vivo transposon mutagenesis system

Photosynthesis Research - Acaryochloris marina MBIC 11017 possesses chlorophyll (Chl) d as a major Chl, which enables this organism to utilize far-red light for photosynthesis. Thus, the adaptation...     

Studies on excitation energy flow in the photosynthetic pigment system; Structure and energy transfer mechanism

Excitation energy flow in photosynthetic pigment systems is discussed in relation to structure of the system and transfer mechanism for each elementary process. Three typical examples for actual transfer processes are shown for the phycobilin system in cyanobacteria, the antenna system of photosynthetic bacteria and the Chla/c antenna system of brown algae. The main analytical method was the time-resolved fluorescence spectroscopy in the picosecond time range. In general, static optical charactersitics are not the main reason for the transfer efficiency, but the structure of the system is a prerequisite for the transfer process. On the phycobilin system, theoretical investigation was compared with experimental analysis, which leads to the essential understanding of the transfer process in terms of quantum mechanics. Recipient of the Botanical Society Award for Young Scientists, 1989.