Water management practices and climate in ancient agriculture: inferences from the stable isotope composition of archaeobotanical remains

Carbon isotope discrimination (Δ¹³C) in charred grains from archaeological sites provides reliable information about water availability of ancient crops. However, as cereals are cultivated plants, they may reflect not only climatic fluctuations, but also the effect on water status of certain agronomic practices, such as sowing in naturally wet soils or irrigation. In this work, we propose a methodological approach to combine Δ¹³C data from different plant species, in order to discriminate between climate-derived and anthropogenic effects on ancient crops. We updated previous models for estimating water inputs from Δ¹³C of cereal grains of Hordeum vulgare and Triticum aestivum/durum, and we applied them to published data from several archaeological sites, including samples from the Neolithic to the present day in northeast and southeast Spain, as well as from the Neolithic site of Tell Halula (northwest Syria). We found an important decrease in water availability from the Neolithic to the present time in the three areas of study, especially clear for the two driest areas (southeast Spain and northwest Syria). Potential differences in water management practices between wheat and barley, as well as between cereal and legume crops (Vicia faba and Lens culinaris), are also discussed on the basis of the comparison of Δ¹³C values across several archaeological sites.     

hunchback and Ikaros-like zinc finger genes control reproductive system development in Caenorhabditis elegans

Here we provide evidence for a C2H2 zinc finger gene family with similarity to Ikaros and hunchback. The founding member of this family is Caenorhabditis elegans ehn-3, which has important and poorly understood functions in somatic gonad development. We examined the expression and function of four additional hunchback/Ikaros-like (HIL) genes in C. elegans reproductive system development. Two genes, ehn-3 and R08E3.4, are expressed in somatic gonadal precursors (SGPs) and have overlapping functions in their development. In ehn-3; R08E3.4 double mutants, we find defects in the generation of distal tip cells, anchor cells, and spermatheca; three of the five tissues derived from the SGPs. We provide in vivo evidence that C. elegans HIL proteins have functionally distinct zinc finger domains, with specificity residing in the N-terminal set of four zinc fingers and a likely protein-protein interaction domain provided by the C-terminal pair of zinc fingers. In addition, we find that a chimeric human Ikaros protein containing the N-terminal zinc fingers of EHN-3 functions in C. elegans. Together, these results lend support to the idea that the C. elegans HIL genes and Ikaros have similar functional domains. We propose that hunchback, Ikaros, and the HIL genes arose from a common ancestor that was present prior to the divergence of protostomes and deuterostomes.     

Association between tree-ring and needle δ<Superscript>13</Superscript>C and leaf gas exchange in <Emphasis Type="Italic">Pinus halepensis</Emphasis> under semi-arid conditions

Associations between δ¹³C values and leaf gas exchanges and tree-ring or needle growth, used in ecophysiological compositions, can be complex depending on the relative timing of CO₂ uptake and subsequent redistribution and allocation of carbon to needle and stem components. For palaeoenvironmental and dendroecological studies it is often interpreted in terms of a simple model of δ¹³C fractionation in C₃ plants. However, in spite of potential complicating factors, few studies have actually examined these relationships in mature trees over inter- and intra-annual time-scales. Here, we present results from a 4 years study that investigated the links between variations in leaf gas-exchange properties, growth, and dated δ¹³C values along the needles and across tree rings of Aleppo pine trees growing in a semi-arid region under natural conditions or with supplemental summer irrigation. Sub-sections of tissue across annual rings and along needles, for which time of formation was resolved from growth rate analyses, showed rapid growth and δ¹³C responses to changing environmental conditions. Seasonal cycles of growth and δ¹³C (up to ~4‰) significantly correlated (P<0.01) with photosynthetically active radiation, vapour pressure deficit, air temperature, and soil water content. The irrigation significantly increased leaf net assimilation, stomatal conductance and needle and tree-ring growth rate, and markedly decreased needle and tree-ring δ¹³C values and its sensitivity to environmental parameters. The δ¹³C estimates derived from gas-exchange parameters, and weighted by assimilation, compared closely with seasonal and inter-annual δ¹³C values of needle- and tree-ring tissue. Higher stomatal conductances of the irrigated trees (0.22 vs. 0.08 mol m⁻² s⁻¹ on average) corresponded with ~2.0‰ lower average δ¹³C values, both measured and derived. Derived and measured δ¹³C values also indicated that needle growth, which occurs throughout the stressful summer was supported by carbon from concurrent, low rate assimilation. For Aleppo pine under semi-arid and irrigated conditions, the δ¹³C of tree-ring and needle material proved, in general, to be a reasonable indicator of integrated leaf gas-exchange properties.     

ADP-ribosylation of actin from the green algaChara corallina byClostridium botulinum C2 toxin andClostridium perfringens iota toxin

Summary The ability of two bacterial toxins to modify a plant actin by covalent ADP-ribosylation was tested in the green algaChara corallina. Using [³²P]NAD, bothClostridium botulinum C2 toxin andClostridium perfringens iota toxin labelled a protein of M_r 42 kDa which comigrated with actin and was immunoprecipitated by a monoclonal anti-actin antibody. ADP-ribosylation ofChara actin was more efficient with iota toxin than with C2 toxin. The actin bundles in perfusedChara cells were not affected by toxin-containing media competent for ADP-ribosylation. The data indicate that monomeric plant actin is substrate for ADP-ribosylation by the bacterial toxins.Abbreviations ADP adenosine-diphosphate - EGTA ethyleneglycol-bis-(-aminoethyl)N,N,N,N-tetraacetic acid - NAD nicotinamide dinucleotide - pCA -log [Ca²⁺] - PIPES piperazine-N,N-bis(2-ethanesulfonic acid) Dedicated to Prof. Dr. Dr. h.c. Eberhard Schnepf on the occasion of his retirement     

The Caenorhabditis elegans FancD2 ortholog is required for survival following DNA damage

Fanconi anemia (FA) is an autosomal recessive disease characterized by bone-marrow failure, congenital abnormalities, and cancer susceptibility. There are 11 FA complementation groups in human where 8 genes have been identified. We found that FancD2 is conserved in evolution and present in the genome of the nematode Caenorhabditis elegans. The gene Y41E3.9 (CeFancD2) encodes a structural ortholog of human FANCD2 and is composed of 10 predicted exons. Our analysis showed that exons 6 and 7 were absent from a CeFancD2 EST suggesting the presence of a splice variant. In an attempt to characterize its role in DNA damage, we depleted worms of CeFANCD2 using RNAi. When the CeFANCD2(RNAi) worms were treated with a crosslinking agent, a significant drop in the progeny survival was noted. These worms were also sensitive, although to a lesser extent, to ionizing radiation (IR). Therefore, these data support an important role for CeFANCD2 in DNA damage response as for its human counterpart. The data also support the usefulness of C. elegans to study the Fanconi anemia pathway, and emphasize the biological importance of FANCD2 in DNA damage response throughout evolution.     

Tracking changing environments using stable carbon isotopes in fossil tooth enamel: an example from the South African hominin sites

The environmental contexts of the karstic hominin sites in South Africa have been established largely by means of faunal associations; taken together these data suggest a trend from relatively closed and more mesic to open, drier environments from about 3 to 1.5 Ma. Vrba argued for a major shift within this trend ca. 2.4-2.6 Ma, an influential proposal that posited links between bovid (and hominin) radiation in Africa and the intensification of Northern Hemisphere Glaciation. Yet faunal approaches often rely on habitat and feeding preferences of modern taxa that may differ from those of their extinct predecessors. Here we explore ways of extending ¹³C/¹²C data from fossil mammals beyond denoting “presence” or “absence” of C₄ grasses using the evolution of open environments in South Africa as a case study. To do so we calculated the relative proportions of C₃-, mixed-, and C₄-feeding herbivores for all the hominin sites for which we have sufficient data based on ¹³C/¹²C analyses of fossil tooth enamel. The results confirm a general trend towards more open environments since 3 Ma, but they also emphasize a marked change to open grassy habitats in the latest Pliocene/early Pleistocene. Mean ¹³C/¹²C for large felids also mirrored this trend.     

Trypanosoma cruzi: Role of macrophage membrane components in the phagocytosis of bloodstream forms

The phagocytosis of Trypanosoma cruzi bloodstream forms is mediated by macrophage Pronase-sensitive membrane components. Trypsin and chymotrypsin treatment of macrophages, which prevents the uptake of T. cruzi culture forms, does not inhibit the phagocytosis of bloodstream parasites. The phagocytosis activity of the macrophages was recovered within 6–8 hr after the removal of Pronase. Inhibition of protein synthesis after Pronase treatment prevents the recovery of the endocytic activity of the macrophages. Fc and C3b receptors are not apparently essential for the phagocytosis of T. cruzi bloodstream forms. The described membrane components may help to explain the tropism of some T. cruzi strains for cells of the mononuclear phagocytic system in the living host.     

Activation of protein kinase C suppresses fragmentation of pig oocytes aged in vitro

When cultured for an extended time, pig oocytes that matured in vitro to the stage of metaphase II undergo the complex process designated as ageing. Under our conditions, some pig oocytes aged 3 days remained at the stage of metaphase II (22%), but others underwent spontaneous parthenogenetic activation (45%), and still others perished through fragmentation (28%) or lysis (5%). Activation of protein kinases C (PKCs) using phorbol-12-myristate-13-acetate (PMA) protects oocytes from fragmentation. None of the oocytes were fragmented after 3 days of aging in 50 nM of PMA. A similar effect (8% of fragmented oocytes) was observed after a 3-day treatment of aging oocytes with 100 μM of 1-stearoyl-2arachidonoyl-sn-glycerol (STEAR). PMA and STEAR activate both calcium-dependent and calcium-independent PKCs. This combined effect on PKCs seems to be essential for the protection of oocytes from fragmentation. Neither the specific activator of calcium-dependent PKCs 1-oleoyl-2-acetyl-sn-glycerol (OLE) nor the specific activator of calcium-independent PKCs dipalmitoyl-l-α-phosphatidylinositol-3,4,5-triphosphate heptaammonium salt (DIPALM) suppressed the fragmentation of aging pig oocytes. Twenty-one percentage of oocytes fragmented when aged for 3 days in 10 μM OLE and 26% of aged oocytes fragmented in 100 nM of DIPALM. However, fragmentation was significantly suppressed to 7% when the oocytes were exposed to the combination of both 10 μM OLE and 100 nM DIPALM. Aging pig oocytes cultured for 1 day with PMA maintained a high capability of being parthenogenetically activated (86% of activated oocytes), using calcium ionophore with 6-dimethylaminopurine. Ageing oocytes treated with PMA also had high capability of cleavage (82%) after their artificial parthenogenetic activation. However, their ability to develop to the stage of blastocyst (12%) was suppressed when compared with oocytes activated immediately after their maturation (29%).