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Ionic liquids (ILs) are a promising alternative to the traditional organic solvents, but their toxic effects cause significant adverse environmental effects and their toxicity assessment have been suggested. The effect of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) on photosynthesis was studied in Arabidopsis thaliana. Apparent effects on chlorosis and inhibition of photosynthetic capacity were observed. As [Bmim][BF4] concentrations increased, a time-dose effect was also observed. The maximum quantum yield (Fv/Fm), and the actual quantum yield of photosystem II (ΦPSII), both decreased; at the same time, the expression of psbA, a key gene of the photosystem II electron transport, was reduced by [Bmim][BF4] treatment. The synthesis of the large and small subunits of Rubisco were not affected by treatment. On the other hand, Rubisco activase (RCA) was significantly suppressed at the transcriptional level. Our results suggest that photochemistry of PSII as well as Rubisco activation are involved in ILs resistance. [ABSTRACT FROM AUTHOR]

Photosynthetic diatoms are exposed to a rapid and unexpected variations in light intensity that can modulate the contents of photosynthetic pigments and the carotenoid profile. In this study, the influence of light availability on photoprotection in the diatom Phaeodactylum tricornutum was investigated. Experimental cultures were exposed to three irradiances (100, 200 and 400 µmol photons m−2 s−1) and two light: dark cycles (12:12 and 24:00 h) that resulted in different light energy daily doses (D = 4.32 mol photons m−2), where the treatments were named in NDxh (N = amount of daily doses D, and x = photoperiod in hours). The samples treated at different doses were compared in terms of cell growth, chlorophyll-a fluorescence, pigment content and gene transcription levels. Specific growth rate was 1.9-fold higher in 8D24h daily dose (34.56 mol photons m−2) with 3 times higher light absorption in comparison to the lowest light energy dose. Also, at higher light intensities the content of chlorophyll-a, fucoxanthin and diadinoxanthin in P. tricornutum was lower, while the regulation of the xanthophyll cycle was achieved by the highest light energy doses. The transcriptional profiles of ZEP1, ZEP2, VDL1 and VDL2 genes were influenced by the highest light energy doses, on the other hand VDE and ZEP3 genes were poorly regulated by light. In addition, a similar transcription pattern was found for two isoforms of ZEP genes as well as in VDL genes. This study demonstrated that light energy doses and irradiances affect the photoacclimation and photoprotection responses. [ABSTRACT FROM AUTHOR]

Climacteric fruit maturation is polygenic, complex process. Gene activity has a significant effect on the quality characteristics of the fruit for harvest and storage. Existing methods generally allow determining the degree of ripeness at harvest (point '0'). Since there is no method defining onset of the climacteric stage of the fruits, an attempt to identify the functional molecular marker that would determine a physiological ripeness of the fruit several days in advance before harvest was conducted. The analysis of changes in transcript of ten selected genes, and evaluation of the correlation of these genes with changes in fruits quality of two apple varieties Golden Delicious (winter cv.) and McIntosh (autumn cv.), allowed to identify a potential marker, activated a few days before harvesting the fruits. Overexpression of the starch glucosidase gene (StG) in the late fruits has been observed prior to the onset of ethylene production. The results confirm that it could be a potential functional marker useful for assessment of physiological ripeness status of cvs Golden Delicious and McIntosh.

The jasmonic acid (JA) pathway is the main signal-transduction pathway induced by insect folivory. Mutant plants affected in the jasmonate pathway (18:0 and/or 16:0-oxylipin routes) were studied to assess the effects of JA and its oxylipin intermediates 12-oxophytodienoic acid (OPDA) and dinor-OPDA (dnOPDA) on interconnected signal-transduction pathways that underlie induced defenses in Arabidopsis. Our data show that the oxylipin jasmonates dnOPDA, OPDA and JA have different roles in defense signaling induced after feeding by the chewing-biting caterpillar Pieris rapae. Jasmonic acid, and not OPDA or dnOPDA, is the major signaling compound required for the induction of the defense-related genes LOX2 ( Lipoxygenase 2), OPR3 ( 12-Oxophytodienoate reductase 3), ACX1 ( Acyl-CoA oxidase 1) and PAL1 ( Phenylalanine ammonia-lyase 1). Monitoring PAL1 transcript levels clearly showed that accumulation of JA upon P. rapae feeding results in the induction of the salicylic acid pathway. Furthermore, JA is the major signaling compound required for the P. rapae-induced expression of the defense-related gene HPL1 ( Hydroperoxide lyase 1). The jasmonate dnOPDA influences the induction of the HPL-branch as well, yet its effect is antagonistic to the effect of JA. Our data show that these jasmonates may be used to fine-tune Arabidopsis' herbivore-induced responses in terms of the HPL-branch from the oxylipin pathway. [ABSTRACT FROM AUTHOR]

To study whether natural variation in Arabidopsis thaliana could be used to dissect the genetic basis of responses to herbivory in terms of induced volatile emissions, nine accessions were characterized upon herbivory by biting-chewing Pieris rapae caterpillars or after treatment with the phytohormone jasmonic acid (JA). Analysis of 73 compounds in the headspace showed quantitative differences in the emission rates of several individual compounds among the accessions. Moreover, variation in the emission of volatile compounds after JA treatment was reflected in the behaviour of the parasitoid Diadegma semiclausum when they were offered the headspace volatiles of several combinations of accessions in two-choice experiments. Accessions also differ in transcript levels of genes that are associated with the emission of plant volatiles. The genes BSMT1 and Cyp72A13 could be connected to the emission of methyl salicylate and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT), respectively. Overall, Arabidopsis showed interesting phenotypic variations with respect to the volatile blend emitted in response to herbivory that can be exploited to identify genes and alleles that underlie this important plant trait. [ABSTRACT FROM PUBLISHER]

Abstract: The prochlorophyte-like cyanobacterium Acaryochloris marina contains two pcb genes, pcbA and pcbC, which encode chlorophyll (Chl) d-binding antenna proteins PcbA and PcbC, respectively. Using real-time reverse transcriptase polymerase chain reaction (RT-PCR), it is shown that when Acaryochloris cells are grown in an iron-deficient medium, the transcription of the pcbC gene is up-regulated compared to that of pcbA. Biochemical and immunological analyses indicated that under the same iron-deficient conditions, the level of Photosystem I (PSI) decreased compared with that of Photosystem II (PSII). Electron microscopy revealed that concomitant with these changes was the formation of Pcb–PSI supercomplexes which, in their largest form, were composed of 18 Pcb subunits forming a ring around the trimeric PSI reaction centre core. Mass spectrometry indicated that the PcbC protein is the main constituent of this outer PSI antenna system. It is therefore concluded that in Acaryochloris, the PcbC protein forms an antenna for PSI when iron levels become limiting and in this way compensates for the drop in the level of PSI relative to PSII which occurs under these conditions. [Copyright &y& Elsevier]