Why are non-photosynthetic tissues generally C enriched compared with leaves in C plants? Review and synthesis of current hypotheses.

Non-photosynthetic, or heterotrophic, tissues in C plants tend to be enriched in C compared with the leaves that supply them with photosynthate. This isotopic pattern has been observed for woody stems, roots, seeds and fruits, emerging leaves, and parasitic plants incapable of net CO fixation. Unlike in C plants, roots of herbaceous C plants are generally not C-enriched compared with leaves.

Rubisco oligomers composed of linked small and large subunits assemble in tobacco plastids and have higher affinities for CO2 and O2.

Manipulation of Rubisco within higher plants is complicated by the different genomic locations of the large (L; rbcL) and small (S; RbcS) subunit genes. Although rbcL can be accurately modified by plastome transformation, directed genetic manipulation of the multiple nuclear-encoded RbcS genes is more challenging. Here we demonstrate the viability of linking the S and L subunits of tobacco (Nicotiana tabacum) Rubisco using a flexible 40-amino acid tether.

Putative functional role for the invariant aspartate 263 residue of Rhodospirillum rubrum Rubisco.

Although aspartate residue D263 of Rhodospirillum rubrum Rubisco is close to the active site and invariant in all reported Rubiscos, its possible functional and structural roles in Rubisco activity have not been investigated. We have mutagenised D263 to several selected amino acids (asparagine, alanine, serine, glutamate, and glutamine) to probe possible roles in facilitating proton movements within the active site and maintaining structural positioning of key active-site groups. The mutants have been characterized by kinetic methods and by differential scanning calorimetry (DSC) to examine the effects of the substitutions on the stability of the folded state.

Characterization of cyclophilin-encoding genes in Phytophthora.

Recent research has shown that cyclophilins, proteins that catalyze the isomerization of peptidyl-prolyl bonds, play a variety of important roles in infection, including facilitating host penetration and colonization and activating pathogen effector proteins within the host cytoplasm. In the current study, bioinformatic analysis of the genomes of three species of plant pathogens in the genus Phytophthora has revealed extensive synteny between the 20 or 21 members of the cyclophilin gene family. In P.

Specific patterns of histone marks accompany X chromosome inactivation in a marsupial.

The inactivation of one of the two X chromosomes in female placental mammals represents a remarkable example of epigenetic silencing. X inactivation occurs also in marsupial mammals, but is phenotypically different, being incomplete, tissue-specific and paternal. Paternal X inactivation occurs also in the extraembryonic cells of rodents, suggesting that imprinted X inactivation represents a simpler ancestral mechanism.

Stomatal responses to CO2 during a diel Crassulacean acid metabolism cycle in Kalanchoe daigremontiana and Kalanchoe pinnata.

To investigate the diurnal variation of stomatal sensitivity to CO2, stomatal response to a 30 min pulse of low CO2 was measured four times during a 24 h time-course in two Crassulacean acid metabolism (CAM) species Kalanchoe daigremontiana and Kalanchoe pinnata, which vary in the degree of succulence, and hence, expression and commitment to CAM. In both species, stomata opened in response to a reduction in pCO2 in the dark and in the latter half of the light period, and thus in CAM species, chloroplast photosynthesis is not required for the stomatal response to low pCO2. Stomata did not respond to a decreased pCO2 in K.

Different thermal sensitivity of the repair of photodamaged photosynthetic machinery in cultured Symbiodinium species.

Coral bleaching caused by heat stress is accompanied by photoinhibition, which occurs under conditions where the rate of photodamage to photosystem II (PSII) exceeds the rate of its repair, in the symbiotic algae (Symbiodinium spp.) within corals. However, the mechanism of heat stress-induced photoinhibition in Symbiodinium still remains poorly understood.

A simple non-invasive protocol to establish primary cell lines from tail and toe explants for cytogenetic studies in Australian dragon lizards (Squamata: Agamidae).

Primary cell lines were established from cultures of tail and toe clips of five species of Australian dragon lizards: Tympanocryptis pinguicolla, Tympanocryptis sp., Ctenophorus fordi, Amphibolurus norrisi and Pogona vitticeps. The start of exponential cell growth ranged from 1 to 5 weeks.

Cone-rod dependence in the rat retina: variation with the rate of rod damage.

Purpose: To assess the effect of accelerated rod damage on the integrity of cones in the rat retina.

Methods: Rhodopsin-mutant P23H-3 and Sprague-Dawley (SD) rats were raised in scotopic ambient conditions (12 hours dark, 12 hours 5 lux) and then exposed to photopic conditions (12 hours dark, 12 hours 300 lux). Rods and cones were assessed for cell death, outer segment (OS) morphology, and electroretinogram (ERG) responses.

Frost tolerance and ice formation in Pinus radiata needles: ice management by the endodermis and transfusion tissues.

Conifers are among the most frost tolerant tree species. Cryo-scanning electron microscopy (cryo-SEM) was used to visualise ice formation in pine needles to better understand how conifer leaves manage extracellular ice. Acclimated and unacclimated needles of Pinus radiata (D.

Invited Review: Cryo-scanning electron microscopy (CSEM) in the advancement of functional plant biology. Morphological and anatomical applications.

Cryo-scanning electron microscopy (CSEM) is reviewed by exploring how the images obtained have changed paradigms of plant functions and interactions with their environment. Its power to arrest and stabilise plant parts in milliseconds, and to preserve them at full hydration for examination at micrometre resolution has changed many views of plant function. For example, it provides the only feasible way of accurately measuring stomatal aperture during active transpiration, and volume and shape changes in guard cells, or examining the contents of laticifers.

Molecular marker suggests rapid changes of sex-determining mechanisms in Australian dragon lizards.

Distribution of sex-determining mechanisms across Australian agamids shows no clear phylogenetic segregation, suggesting multiple transitions between temperature-dependent (TSD) and genotypic sex determination (GSD). These taxa thus present an excellent opportunity for studying the evolution of sex chromosomes, and evolutionary transitions between TSD and GSD. Here we report the hybridization of a 3 kb genomic sequence (PvZW3) that marks the Z and W microchromosomes of the Australian central bearded dragon (Pogona vitticeps) to chromosomes of 12 species of Australian agamids from eight genera using fluorescence in-situ hybridization (FISH).

Spatial biases and computational constraints on the encoding of complex local image structure.

The decomposition of visual scenes into elements described by orientation and spatial frequency is well documented in the early cortical visual system. How such 2nd-order elements are sewn together to create perceptual objects such as corners and intersections remains relatively unexplored. The current study combines information theory with structured deterministic patterns to gain insight into how complex (higher-order) image features are encoded.

On the metabolic origin of the carbon isotope composition of CO2 evolved from darkened light-acclimated leaves in Ricinus communis.

The (13)C isotopic signature (delta(13)C) of CO(2) respired from plants is widely used to assess carbon fluxes and ecosystem functioning. There is, however, a lack of knowledge of the metabolic basis of the delta(13)C value of respired CO(2). To elucidate the physiological mechanisms driving (12)C/(13)C fractionation during respiration, the delta(13)C of respired CO(2) from dark-acclimated leaves during the night, from darkened leaves during the light period, and from stems and roots of Ricinus communis was analysed.

Life history of cones in the rhodopsin-mutant P23H-3 rat: evidence of long-term survival.

Purpose: To follow the status of cones over the life of the P23H-3 transgenic rat, while the rod population is depleted.

Methods: P23H-3 heterozygous and Sprague-Dawley (SD) control rats were raised in dim, cyclic light from postnatal day (P)10 to P540. Retinas were examined for cone density, cone outer segment (OS) length, cone axon and soma morphology, and the amplitude of rod and cone components of the electroretinogram (ERG) were determined.

Effects of cocaine on honey bee dance behaviour.

The role of cocaine as an addictive drug of abuse in human society is hard to reconcile with its ecological role as a natural insecticide and plant-protective compound, preventing herbivory of coca plants (Erythroxylum spp.). This paradox is often explained by proposing a fundamental difference in mammalian and invertebrate responses to cocaine, but here we show effects of cocaine on honey bees (Apis mellifera L.

Mechanism of somatic hypermutation: critical analysis of strand biased mutation signatures at A:T and G:C base pairs.

The DNA sequence data of the somatic hypermutation (SHM) field published since 1984 has been critically reviewed. The analysis has revealed three strand biased mutation signatures. The first concerns the mutations generated at G:C base pairs in mice genetically deficient in uracil-DNA glycosylase and MSH2-MSH6-mediated mismatch repair.

Characterization of TCTP, the translationally controlled tumor protein, from Arabidopsis thaliana.

The translationally controlled tumor protein (TCTP) is an important component of the TOR (target of rapamycin) signaling pathway, the major regulator of cell growth in animals and fungi. TCTP acts as the guanine nucleotide exchange factor of the Ras GTPase Rheb that controls TOR activity in Drosophila melanogaster. We therefore examined the role of Arabidopsis thaliana TCTP in planta.

Nitrogen in cell walls of sclerophyllous leaves accounts for little of the variation in photosynthetic nitrogen-use efficiency.

Photosynthetic rate per unit nitrogen generally declines as leaf mass per unit area (LMA) increases. To determine how much of this decline was associated with allocating a greater proportion of leaf nitrogen into cell wall material, we compared two groups of plants. The first group consisted of two species from each of eight genera, all of which were perennial evergreens growing in the Australian National Botanic Gardens (ANBG).

Transient shade and drought have divergent impacts on the temperature sensitivity of dark respiration in leaves of Geum urbanum.

The respiratory response of plants to temperature is a critical biotic feedback in the study of global climate change. Few studies, however, have investigated the effects of environmental stresses on the short-term temperature response of dark respiration (R) at the leaf level. We investigated the effect of shade and transient drought on the temperature sensitivity (Q; the proportional increase in respiration per 10°C increase in temperature) of R of Geum urbanum L.

Computational prediction of candidate miRNAs and their targets from Medicago truncatula non-protein-coding transcripts.

Identification and analysis of miRNAs enhances our understanding of the important roles that small RNAs play in complex regulatory networks. It is often difficult to perform large-scale validation of miRNA expression that is predicted from genomic regions. Expressed transcripts provide an alternative resource to facilitate identification of miRNAs and their targets.

Microarray analysis identifies candidate genes for key roles in coral development.

Background: Anthozoan cnidarians are amongst the simplest animals at the tissue level of organization, but are surprisingly complex and vertebrate-like in terms of gene repertoire. As major components of tropical reef ecosystems, the stony corals are anthozoans of particular ecological significance. To better understand the molecular bases of both cnidarian development in general and coral-specific processes such as skeletogenesis and symbiont acquisition, microarray analysis was carried out through the period of early development - when skeletogenesis is initiated, and symbionts are first acquired.

Variability of a dynamic visual signal: the fiddler crab claw-waving display.

Fiddler crabs use elaborate, species-specific claw-waving displays to communicate with rivals and mates. However, detailed comparative studies of fiddler crab signal structure and structural variations are lacking. This paper provides an analysis of the claw-waving displays of seven Australian species of fiddler crab, Uca mjoebergi, U.

Dynamic flexibility in the structure and function of photosystem II in higher plant thylakoid membranes: the grana enigma.

Grana are not essential for photosynthesis, yet they are ubiquitous in higher plants and in the recently evolved Charaphyta algae; hence grana role and its need is still an intriguing enigma. This article discusses how the grana provide integrated and multifaceted functional advantages, by facilitating mechanisms that fine-tune the dynamics of the photosynthetic apparatus, with particular implications for photosystem II (PSII). This dynamic flexibility of photosynthetic membranes is advantageous in plants responding to ever-changing environmental conditions, from darkness or limiting light to saturating light and sustained or intermittent high light.

Physical map of two tammar wallaby chromosomes: a strategy for mapping in non-model mammals.

Marsupials are especially valuable for comparative genomic studies of mammals. Two distantly related model marsupials have been sequenced: the South American opossum (Monodelphis domestica) and the tammar wallaby (Macropus eugenii), which last shared a common ancestor about 70 Mya. The six-fold opossum genome sequence has been assembled and assigned to chromosomes with the help of a cytogenetic map.