P. Oxy. LXXXIV 5476 – 'Gryllos'?

In The Oxyrhynchus Papyri 84 (London 2019), H. Whitehouse published a papyrus containing one word and a drawing (‘P. Oxy. 5476: The Argonauts’ Boat on Wheels’). She connected the piece with the world of entertainment, more precisely, in her view, the papyrus perhaps served as the advertisement for a forthcoming dramatic performance. This paper presents another interpretation of the papyrus by drawing parallels to other pieces, which can be collected under the term ‘Grylloi.

Notes on P. Oxy. XXIX 2506: Comment on Lyric Poems

P. Oxy. XXIX 2506 is a manuscript of the first or early second century A.D. It contains a commentary on Greek poetry. This article presents attempts of identifying some new poetic fragments and of reconstructing several parts of the commentary respectively the passages of poetry quoted within it

Release rates of trace elements and protein from decomposing planktonic debris. 2. Copepod carcasses and sediment trap particulate matter

In experiments designed to relate the release kinetics of various elements with that of protein from biogenic particles, 110mAg, 241Am, 109Cd, 60Co, 75Se and protein were measured over time in radiolabeled copepod carcasses and particles caught in unpoisoned sediment traps (mostly zooplankton fecal pellets and amorphous marine snow). Log-linear release rate constants (k) of 110mAg, 241Am, 109Cd, and 60Co from carcasses ranged from 0.079 d−1 for 60Co at 2°C to 0.130 d−1 for 109Cd at 15°C, and did not vary significantly with temperature. 75Se was lost most rapidly from copepod carcasses at 2°C, with k = 0.168 d−1; however, at 15°C, 75Se was in two compartments, with 56% in a rapidly exchanging pool (k = 0.391 d−1) and 44% in a slowly exchanging pool (k = 0.107 d−1). Protein displayed loss from two compartments at both temperatures. At 2°C, protein was lost slowly (k = 0.065 d−1) for 1 wk, after which it was released from the carcasses very rapidly (k = 0.245 d−1). At 15°C, however, the loss of protein from carcasses was more rapid over the first 2 d (k = 0.627 d−1) than thereafter (k = 0.127 d−1). The k values of 110mAg, 241Am, and 60Co from sediment trap particles (15°C) ranged from 0.008 to 0.011 d−1. Protein was lost twice as fast as 110mAg, 241Am, and 60Co, more slowly than half of the particulate 109Cd and 75Se in rapidly exchanging pools (k = 0.168 and 0.237 d−1, respectively), and at rates comparable to 109Cd and 75Se in slowly exchanging pools. Overall, copepod carcasses and fecal pellets could act as vectors of these five elements and protein to the deep ocean, the vertical flux being dependent on settling velocity and water column temperature structure. Of the elements considered here, Se follows the cycling of protein most closely

Characteristics of C-4 photosynthesis in stems and petioles of C-3 flowering plants

Most plants are known as C-3 plants because the first product of photosynthetic CO2 fixation is a three-carbon compound. C-4 plants, which use an alternative pathway in which the first product is a four-carbon compound, have evolved independently many times and are found in at least 18 families. In addition to differences in their biochemistry, photosynthetic organs of C-4 plants show alterations in their anatomy and ultrastructure. Little is known about whether the biochemical or anatomical characteristics of C-4 photosynthesis evolved first. Here we report that tobacco, a typical C-3 plant, shows characteristics of C-4 photosynthesis in cells of stems and petioles that surround the xylem and phloem, and that these cells are supplied with carbon for photosynthesis from the vascular system and not from stomata. These photosynthetic cells possess high activities of enzymes characteristic of C-4 photosynthesis, which allow the decarboxylation of four-carbon organic acids from the xylem and phloem, thus releasing CO2 for photosynthesis. These biochemical characteristics of C-4 photosynthesis in cells around the vascular bundles of stems of C-3 plants might explain why C-4 photosynthesis has evolved independently many times

Evolution and Functional Diversification of Fructose Bisphosphate Aldolase Genes in Photosynthetic Marine Diatoms

Diatoms and other chlorophyll-c containing, or chromalveolate, algae are among the most productive and diverse phytoplankton in the ocean. Evolutionarily, chlorophyll-c algae are linked through common, although not necessarily monophyletic, acquisition of plastid endosymbionts of red as well as most likely green algal origin. There is also strong evidence for a relatively high level of lineage-specific bacterial gene acquisition within chromalveolates. Therefore, analyses of gene content and derivation in chromalveolate taxa have indicated particularly diverse origins of their overall gene repertoire. As a single group of functionally related enzymes spanning two distinct gene families, fructose 1,6-bisphosphate aldolases (FBAs) illustrate the influence on core biochemical pathways of specific evolutionary associations among diatoms and other chromalveolates with various plastid-bearing and bacterial endosymbionts. Protein localization and activity, gene expression, and phylogenetic analyses indicate that the pennate diatom Phaeodactylum tricornutum contains five FBA genes with very little overall functional overlap. Three P. tricornutum FBAs, one class I and two class II, are plastid localized, and each appears to have a distinct evolutionary origin as well as function. Class I plastid FBA appears to have been acquired by chromalveolates from a red algal endosymbiont, whereas one copy of class II plastid FBA is likely to have originated from an ancient green algal endosymbiont. The other copy appears to be the result of a chromalveolate-specific gene duplication. Plastid FBA I and chromalveolate-specific class II plastid FBA are localized in the pyrenoid region of the chloroplast where they are associated with β-carbonic anhydrase, which is known to play a significant role in regulation of the diatom carbon concentrating mechanism. The two pyrenoid-associated FBAs are distinguished by contrasting gene expression profiles under nutrient limiting compared with optimal CO2 fixation conditions, suggestive of a distinct specialized function for each. Cytosolically localized FBAs in P. tricornutum likely play a role in glycolysis and cytoskeleton function and seem to have originated from the stramenopile host cell and from diatom-specific bacterial gene transfer, respectively

Predictable ecological response to rising CO2 of a community of marine phytoplankton

Rising atmospheric CO2 and ocean acidification are fundamentally altering conditions for life of all marine organisms, including phytoplankton. Differences in CO2 related physiology between major phytoplankton taxa lead to differences in their ability to take up and utilize CO2. These differences may cause predictable shifts in the composition of marine phytoplankton communities in response to rising atmospheric CO2. We report an experiment in which seven species of marine phytoplankton, belonging to four major taxonomic groups (cyanobacteria, chlorophytes, diatoms, and coccolithophores), were grown at both ambient (500 ?atm) and future (1,000 ?atm) CO2 levels. These phytoplankton were grown as individual species, as cultures of pairs of species and as a community assemblage of all seven species in two culture regimes (high?nitrogen batch cultures and lower?nitrogen semicontinuous cultures, although not under nitrogen limitation). All phytoplankton species tested in this study increased their growth rates under elevated CO2 independent of the culture regime. We also find that, despite species?specific variation in growth response to high CO2, the identity of major taxonomic groups provides a good prediction of changes in population growth and competitive ability under high CO2. The CO2?induced growth response is a good predictor of CO2?induced changes in competition (R2 > .93) and community composition (R2 > .73). This study suggests that it may be possible to infer how marine phytoplankton communities respond to rising CO2 levels from the knowledge of the physiology of major taxonomic groups, but that these predictions may require further characterization of these traits across a diversity of growth conditions. These findings must be validated in the context of limitation by other nutrients. Also, in natural communities of phytoplankton, numerous other factors that may all respond to changes in CO2, including nitrogen fixation, grazing, and variation in the limiting resource will likely complicate this prediction

Agrobacterium tumefaciens-mediated transformation of Cleome gynandra L., a C4 dicotyledon that is closely related to Arabidopsis thaliana

In leaves of most C4 plants, the biochemistry of photosynthesis is partitioned between mesophyll and bundle sheath cells. In addition, their cell biology and development also differs from that in C3 plants. We have a poor understanding of the mechanisms that generate the cell-specific accumulation of proteins used in the C4 pathway, and there are few genes that have been shown to be important for the cell biology and development of C4 leaves. To facilitate functional analysis of C4 photosynthesis, and to enable knowledge from Arabidopsis thaliana to be translated to C4 species, an Agrobacterium tumefaciens-mediated transformation protocol was developed for the C4 species Cleome gynandra. A. tumefaciens, harbouring the binary vector SLJ1006, was used to transfer the uidA gene under the control of the CaMV 35S promoter into C. gynandra. Co-incubation of hypocotyls or cotyledons with SLJ1006 allowed efficient transfer of DNA into C. gynandra, and media that allowed callus production and then shoot regeneration were identified. Stable transformants of C. gynandra with detectable amounts of β-glucuronidase (GUS) were produced at an efficiency of 14%. When driven by the CaMV 35S promoter, GUS was visible in all leaf cells, whereas uidA translationally fused to a CgRbcS gene generated GUS accumulation specifically in bundle sheath cells. This transformation procedure is the first for an NAD-ME type C4 plant and should significantly accelerate the analysis of mechanisms underlying C4 photosynthesis

Amphipod susceptibility to metals: Cautionary tales

Heavy metals accumulated by aquatic crustaceans in environmental studies are normally investigated using the whole body burden, with little regard paid to uptake in different tissues, to potential gender of life stage differences, or to the influence of nutrition on the test organism. This is likely to give erroneous conclusions for a dose–response relationship within the toxicity test and potentially lead to wrong conclusions for the ecological risks of metals where species may have higher sensitivities with gender and life stage than indicated or that functionally metals may be sequestered into parts of the body so are not bioavailable. This could lead to under-estimation or over-estimation of the toxicity of metals,respectively, inaccuracy of metal budget calculations and evaluation of trophic transfers of metals. This study evaluated the influences of life stage, gender, and a priori nutritional state in the uptake of the metals zinc (an essential micro-nutrient; Zn) and cadmium (a non-essential element; Cd) in the amphipod Echinogammarus marinus. The study showed that life stage, and nutritional stage did significantly influence the uptake and bioaccumulation for both metals, but only Cd showed differential uptake and bioaccumulation with gender. In addition, it was concluded that there was a significant uptake and accumulation of both metals within the exoskeleton of the amphipods, which though adding to the full body burden would add little to toxicity through lack of bioavailability. These results showed that care should be taken when interpreting results from tests normally preformed on such test organisms

Pyrenoid loss impairs carbon-concentrating mechanism induction and alters primary metabolism in Chlamydomonas reinhardtii

Carbon-concentrating mechanisms (CCMs) enable efficient photosynthesis and growth in CO2-limiting environments, and in eukaryotic microalgae localisation of Rubisco to a microcompartment called the pyrenoid is key. In the model green alga Chlamydomonas reinhardtii, Rubisco preferentially relocalises to the pyrenoid during CCM induction and pyrenoid-less mutants lack a functioning CCM and grow very poorly at low CO2. The aim of this study was to investigate the CO2 response of pyrenoid-positive (pyr+) and pyrenoid-negative (pyr–) mutant strains to determine the effect of pyrenoid absence on CCM induction and gene expression. Shotgun proteomic analysis of low-CO2-adapted strains showed reduced accumulation of some CCM-related proteins, suggesting that pyr– has limited capacity to respond to low-CO2 conditions. Comparisons between gene transcription and protein expression revealed potential regulatory interactions, since Rubisco protein linker (EPYC1) protein did not accumulate in pyr– despite increased transcription, while elements of the LCIB/LCIC complex were also differentially expressed. Furthermore, pyr− showed altered abundance of a number of proteins involved in primary metabolism, perhaps due to the failure to adapt to low CO2. This work highlights two-way regulation between CCM induction and pyrenoid formation, and provides novel candidates for future studies of pyrenoid assembly and CCM function