Photosynthesis Research (v.114, #3)

Study of the effect of reducing conditions on the initial chlorophyll fluorescence rise in the green microalgae Chlamydomonas reinhardtii by T. K. Antal; A. Kolacheva; A. Maslakov; G. Yu. Riznichenko; T. E. Krendeleva; A. B. Rubin (143-154).
Incubation of Chlamydomonas reinhardtii cells under nutrient deficiency results in the faster initial rise in the light-induced chlorophyll fluorescence kinetic curve. We showed that short-term anaerobic incubation of algal cells altered initial fluorescence in a way similar to nutrient starvation, suggesting an important role of the plastoquinones redox state in the observed effect. Bi-component analysis of highly resolved initial fluorescence rise kinetics in sulfur- or oxygen-depleted C. reinhardtii cells suggested that one of the mechanisms underlying the observed phenomenon involves primary closure (photochemical inactivation via Qa reduction) of β-type PSII as compared to α-PSII. Moreover, results of modeling of the fluorescence curve brought us to the conclusion that accumulation of closed centers in α-PSII supercomplexes may also cause a faster initial fluorescence rise. The observed correlations between nutrient supply rate and initial fluorescence rise pattern in green algae can serve to characterize culture nutritional status in vivo.
Keywords: Chlamydomonas reinhardtii ; Sulfur deprivation; Chlorophyll fluorescence; PQ pool redox state; OEC integrity

Purple bacteria have peripheral light-harvesting (PLH) complexes adapted to high-light (LH2) and low-light (LH3, LH4) growth conditions. The latter two have only been fully characterised in Rhodopseudomonas acidophila 7050 and Rhodopseudomonas palustris CGA009, respectively. It is known that LH4 complexes are expressed under the control of two light sensing bacteriophytochromes (BphPs). Recent genomic sequencing of a number of Rps. palustris strains has provided extensive information on PLH genes. We show that both LH3 and LH4 complexes are present in Rps. palustris and have evolved in the same operon controlled by the two adjacent BphPs. Two rare marker genes indicate that a gene cluster CL2, containing LH2 genes and the BphP RpBphP4, was internally transferred within the genome to form a new operon CL1. In CL1, RpBphP4 underwent gene duplication to RpBphP2 and RpBphP3, which evolved to sense light intensity rather than spectral red/far-red intensity ratio. We show that a second LH2 complex was acquired in CL1 belonging to a different PLH clade and these two PLH complexes co-evolved together into LH3 or LH4 complexes. The near-infrared spectra provide additional support for our conclusions on the evolution of PLH complexes based on genomic data.
Keywords: Light-harvesting; Bacteriophytochrome; Low-light; Genome; Evolution; Photosynthesis

A new type of multi-color PAM chlorophyll fluorometer (Schreiber et al. 2012) was applied for measurements of photodamage to photosystem II (PS II) in optically thin suspensions of Chlorella (200 μg Chl l−1) in the presence of 1 mM lincomycin. An action spectrum of the relative decrease of F v/F m in the 440–625 nm range was measured, which not only showed the expected high activity in the blue, but at a lower level also substantial activity above 540 nm. With the same dilute suspension, a PS II absorption spectrum was derived via measurements of the O-I1 rise kinetics induced by differently colored strong light at defined incident quantum flux densities. After normalization of the two spectra at 625 nm, the relative extent of photodamage at 440–480 nm proved substantially higher than absorption by PS II, whereas the two spectra were close to identical in the 540–625 nm range. Hence, overall photodamage to PS II appears to consist of two components, one of which is due to light absorbed by PS II pigments, whereas the other one is likely to involve direct light absorption by Mn in the oxygen-evolving complex (Hakala et al. Biochim Biophys Acta 1706:68–80, 2005). Based on this rationale, an action spectrum of the Mn mechanism of photodamage was deconvoluted from the overall action spectrum, declining steeply above 480 nm. An almost identical Mn-spectrum was derived by another approach with the PAR of the various colors being adjusted to give identical rates of PS II turnover, PAR II. The tentative, basic assumption of negligibly small contribution of the Mn mechanism to photodamage above 540 nm was supported by supplementary measurements using an external 665 nm lamp. 665 nm not only gave about two times PS II turnover as compared to 625 nm, but also about two times photodamage.
Keywords: Absorption cross-section of PS II; Chlorella ; Chlorophyll fluorescence; Mn absorption; O-I1 fluorescence rise; PAR; Photoinhibition

A variety of glycolipids in green photosynthetic bacteria by Tadashi Mizoguchi; Jiro Harada; Taichi Yoshitomi; Hitoshi Tamiaki (179-188).
The compositions of glycolipids in the following seven strains of green photosynthetic bacteria were investigated at the molecular level using LC–MS coupled with an evaporative light scattering detector: Chlorobium (Chl.) limicola strains Larsen (30 °C as the optimal cultivation temperature) and DSM245 (30 °C), Chlorobaculum (Cba.) tepidum strain ATCC49652 (45 °C), Cba. parvum strain NCIB8327 (30 °C), Cba. limnaeum strain 1549 (30 °C), Chl. phaeovibrioides DSM269 (30 °C), and Chloroflexus (Cfl.) aurantiacus strain J-10-fl (55 °C). Dependence of the molecular structures of glycolipids including the chain-length of their acyl groups upon bacterial cultivation temperatures was clearly observed. The organisms with their optimal temperatures of 30, 45, and 55 °C dominantly accumulated glycolipids possessing the acyl chains in the range of C15–C16, C16–C17, and C18–C20, respectively. Cba. tepidum with an optimal temperature of 45 °C preferred the insertion of a methylene group to produce finally a C17-cyclopropane chain. Cfl. aurantiacus cultured optimally at 55 °C caused a drastic increase in the chain-length. Notably, the length of such acyl groups corresponded to that of the esterifying chain in the 17-propionate residues of self-aggregative bacteriochlorophylls-c/d/e, indicating stabilization of their supramolecular structures through hydrophobic interactions among those hydrocarbon chains. Based on the detailed compositions of glycolipids, a survival strategy of green photosynthetic bacteria grown in the wide range of temperatures is discussed.
Keywords: Monogalactosyldiacylglyceride; Rhamnosylgalactosyldiacylglyceride; Bacteriochlorophyll-c/d/e ; Fatty acid; 17-Propionate; Green photosynthetic bacteria; Chlorosome

The effect of stepwise increments of red light intensities on pulse-amplitude modulated (PAM) chlorophyll (Chl) fluorescence from leaves of A. thaliana and Z. mays was investigated. Minimum and maximum fluorescence were measured before illumination (F 0 and F M, respectively) and at the end of each light step ( $$ F^{prime}_{0} $$ and $$ F^{prime}_{ ext{M}} $$ , respectively). Calculated $$ F^{prime}_{0} $$ values derived from F 0, F M and $$ F^{prime}_{ ext{M}} $$ fluorescence according to Oxborough and Baker (1997) were lower than the corresponding measured $$ F^{prime}_{0} $$ values. Based on the concept that calculated $$ F^{prime}_{0} $$ values are under-estimated because the underlying theory ignores PSI fluorescence, a method was devised to gain relative PSI fluorescence intensities from differences between calculated and measured $$ F^{prime}_{0} $$ . This method yields fluorometer-specific PSI data as its input data (F 0, F M, $$ F^{prime}_{0} $$ and $$ F^{prime}_{ ext{M}} $$ ) depend solely on the spectral properties of the fluorometer used. Under the present conditions, the PSI contribution to F 0 fluorescence was 0.24 in A. thaliana and it was independent on the light acclimation status; the corresponding value was 0.50 in Z. mays. Correction for PSI fluorescence affected Z. mays most: the linear relationship between PSI and PSII photochemical yields was clearly shifted toward the one-to-one proportionality line and maximum electron transport was increased by 50 %. Further, correction for PSI fluorescence increased the PSII reaction center-specific parameter, 1/F 0 − 1/F M, up to 50 % in A. thaliana and up to 400 % in Z. mays.
Keywords: C4 photosynthesis; Light-response curve; PAM fluorescence; Photosynthesis; Quantum yield for photochemistry

On June 26–27, 2012, one of us (BBB) made a video based on an interview conducted with Andrew A. Benson, Professor Emeritus, Scripps Institution of Oceanography, University of California, San Diego, CA, USA. The video was first shown in a seminar presented by BBB on July 27, 2012 at the Calvin Laboratory, University of California, Berkeley, to mark the departure of the Energy Biosciences Institute to a new building. Here we record the conversation taking place during the interview. The Brancraft Library on the Berkeley campus will house the video’s transcript in its oral histories collection, and the video will be housed in its motion picture collection. The video and the transcript have also been posted on You Tube ( ).
Keywords: Andrew Benson; Melvin Calvin; Calvin–Benson Cycle; CO2 fixation; 3-phosphoglyceric acid; Ribulose-1,5-bisphosphate