Salivary gland structure of \u3ci\u3eCtenarytaina eucalypti\u3c/i\u3e (MASKELL, 1890) (Hemiptera) and phloem exudate in \u3ci\u3eEucalyptus globulus\u3c/i\u3e LABILLARDIÈRE, 1799 (Myrtaceae)

The structure of the salivary glands of the free-living aphalarid Ctenarytaina eucalypti, which infests multiple species of Eucalyptus in Australasia and has been introduced into many other regions of the world, is described and illustrated. The principal salivary gland is multilobed whereas the accessory gland is tubular. 1-D electrophoresis revealed proteins of approximately 58 and 64 kDa in the salivary gland extracts and proteins of similar molecular weights in the extracted plant exudates, including phloem, from infested leaves and tender shoots of E. globulus. Proteins that could fall within this range include, but are not limited to, glucosemethanol- choline-oxidoreductase (53-66 kDa), Zn-binding dehydrogenase (67 kDa) and esterase (65-96 kDa), in addition to cytochrome P-450 (50-55 kDa), trehalase (56 kDa), amylase (50-75 kDa) and lipase (48-52 kDa). Previous studies indicate that glucose-methanol-cholineoxidoreductase, Zn-binding dehydrogenase, cytochrome P-450 and trehalase suppress plantdefence mechanisms, whereas the cell-degrading enzymes such as amylase, lipase and esterase have a possible role in enabling C. eucalypti to insert its stylet into leaf and shoot tissues of E. globulus

A new simple method for labeling field crops with stable isotope tracers

Numerous systems have been used to label plants with 13C, which differ in design and complexity depending upon the desired experimental goals. However, most of these systems have generally been applied to greenhouse grown plants. Here, we report on a relatively simple 13C labeling system designed to label crops such as switchgrass (Panicum virgatum L.) grown in the greenhouse or small field plots. The main goals of this study were to validate the system and establish performance benchmarks. We constructed and field tested a simple design plexiglass chamber that was sealed at the soil level with a buried rubber apron. Chamber air was circulated through an infrared gas analyzer to monitor CO2 levels within the chamber. Provisions were made to control temperatures and minimize condensation inside the chamber during labeling. Control experiments using the empty chamber both under greenhouse and field settings showed that decline in CO2 levels was only due to plant CO2 absorption and not due to leakage. Results indicated that the system had generally suitable performance characteristics in both greenhouse and field settings. Isotope enrichment data from our studies revealed that switchgrass fixed 13CO2 that was injected into the chamber within 15-20 min labeling periods. The mean and standard deviation of leaf ᵹ13C values across nine plants enclosed in the chamber was 34 ± 8.9 and 96.1 ± 23.6 for the single and double labeling experiments, respectively. Results indicate that a chamber of this construction type can be effectively used also for labeling other crop plants

Molecular and phenotypic characterization of transgenic wheat and sorghum events expressing the barley alanine aminotransferase

Main conclusion — The expression of a barley alanine aminotransferase gene impacts agronomic outcomes in a C3 crop, wheat. The use of nitrogen-based fertilizers has become one of the major agronomic inputs in crop production systems. Strategies to enhance nitrogen assimilation and flux in planta are being pursued through the introduction of novel genetic alleles. Here an Agrobacterium-mediated approach was employed to introduce the alanine aminotransferase from barley (Hordeum vulgare), HvAlaAT, into wheat (Triticum aestivum) and sorghum (Sorghum bicolor), regulated by either constitutive or root preferred promoter elements. Plants harboring the transgenic HvAlaAT alleles displayed increased alanine aminotransferase (alt) activity. The enhanced alt activity impacted height, tillering and significantly boosted vegetative biomass relative to controls in wheat evaluated under hydroponic conditions, where the phenotypic outcome across these parameters varied relative to time of year study was conducted. Constitutive expression of HvAlaAT translated to elevation in wheat grain yield under field conditions. In sorghum, expression of HvAlaAT enhanced enzymatic activity, but no changes in phenotypic outcomes were observed. Taken together these results suggest that positive agronomic outcomes can be achieved through enhanced alt activity in a C3 crop, wheat. However, the variability observed across experiments under greenhouse conditions implies the phenotypic outcomes imparted by the HvAlaAT allele in wheat may be impacted by environment

Seasonal switchgrass ecotype contributions to soil organic carbon, deep soil microbial community composition and rhizodeposit uptake during an extreme drought

The importance of rhizodeposit C and associated microbial communities in deep soil C stabilization is relatively unknown. Phenotypic variability in plant root biomass could impact C cycling through belowground plant allocation, rooting architecture, and microbial community abundance and composition. We used a pulse-chase 13C labeling experiment with compound-specific stable-isotope probing to investigate the importance of rhizodeposit C to deep soil microbial biomass under two switchgrass ecotypes (Panicum virgatum L., Kanlow and Summer) with contrasting root morphology. We quantified root phenology, soil microbial biomass (phospholipid fatty acids, PLFA), and microbial rhizodeposit uptake (13C-PLFAs) to 150 cm over one year during a severe drought. The lowland ecotype, Kanlow, had two times more root biomass with a coarser root system compared to the upland ecotype, Summer. Over the drought, Kanlow lost 78% of its root biomass, while Summer lost only 60%. Rhizosphere microbial communities associated with both ecotypes were similar. However, rhizodeposit uptake under Kanlow had a higher relative abundance of gram-negative bacteria (44.1%), and Summer rhizodeposit uptake was primarily in saprotrophic fungi (48.5%). Both microbial community composition and rhizodeposit uptake shifted over the drought into gram-positive communities. Rhizosphere soil C was greater one year later under Kanlow due to turnover of unlabeled structural root C. Despite a much greater root biomass under Kanlow, rhizosphere δ13C was not significantly different between the two ecotypes, suggesting greater microbial C input under the finer rooted species, Summer, whose microbial associations were predominately saprotrophic fungi. Ecotype specific microbial communities can direct rhizodeposit C flow and C accrual deep in the soil profile and illustrate the importance of the microbial community in plant strategies to survive environmental stress such as drought

Next-Generation Sequencing of Crown and Rhizome Transcriptome from an Upland, Tetraploid Switchgrass

The crown and rhizome transcriptome of an upland tetraploid switchgrass cultivar cv Summer well adapted to the upper Midwest was investigated using the Roche 454-FLX pyrosequencing platform. Overall, approximately one million reads consisting of 216 million bases were assembled into 27,687 contigs and 43,094 singletons. Analyses of these sequences revealed minor contamination with non-plant sequences (\u3c 0.5%), indicating that a majority were for transcripts coded by the switchgrass genome. Blast2Gos comparisons resulted in the annotation of ~65% of the contig sequences and ~40% of the singleton sequences. Contig sequences were mostly homologous to other plant sequences, dominated by matches to Sorghum bicolor genome. Singleton sequences, while displaying significant matches to S. bicolor, also contained sequences matching non-plant species. Comparisons of the 454 dataset to existing EST collections resulted in the identification of 30,177 new sequences. These new sequences coded for a number of different proteins and a selective analysis of two categories, namely, peroxidases and transcription factors, resulted in the identification of specific peroxidases and a number of low-abundance transcription factors expected to be involved in chromatin remodeling. KEGG maps for glycolysis and sugar metabolism showed high levels of transcript coding for enzymes involved in primary metabolism. The assembly provided significant insights into the status of these tissues and broadly indicated that there was active metabolism taking place in the crown and rhizomes at post-anthesis, the seed maturation stage of plant development

Seasonal switchgrass ecotype contributions to soil organic carbon, deep soil microbial community composition and rhizodeposit uptake during an extreme drought

The importance of rhizodeposit C and associated microbial communities in deep soil C stabilization is relatively unknown. Phenotypic variability in plant root biomass could impact C cycling through belowground plant allocation, rooting architecture, and microbial community abundance and composition. We used a pulse-chase 13C labeling experiment with compound-specific stable-isotope probing to investigate the importance of rhizodeposit C to deep soil microbial biomass under two switchgrass ecotypes (Panicum virgatum L., Kanlow and Summer) with contrasting root morphology. We quantified root phenology, soil microbial biomass (phospholipid fatty acids, PLFA), and microbial rhizodeposit uptake (13C-PLFAs) to 150 cm over one year during a severe drought. The lowland ecotype, Kanlow, had two times more root biomass with a coarser root system compared to the upland ecotype, Summer. Over the drought, Kanlow lost 78% of its root biomass, while Summer lost only 60%. Rhizosphere microbial communities associated with both ecotypes were similar. However, rhizodeposit uptake under Kanlow had a higher relative abundance of gram-negative bacteria (44.1%), and Summer rhizodeposit uptake was primarily in saprotrophic fungi (48.5%). Both microbial community composition and rhizodeposit uptake shifted over the drought into gram-positive communities. Rhizosphere soil C was greater one year later under Kanlow due to turnover of unlabeled structural root C. Despite a much greater root biomass under Kanlow, rhizosphere δ13C was not significantly different between the two ecotypes, suggesting greater microbial C input under the finer rooted species, Summer, whose microbial associations were predominately saprotrophic fungi. Ecotype specific microbial communities can direct rhizodeposit C flow and C accrual deep in the soil profile and illustrate the importance of the microbial community in plant strategies to survive environmental stress such as drought

Salivary gland structure of \u3ci\u3eCtenarytaina eucalypti\u3c/i\u3e (MASKELL, 1890) (Hemiptera) and phloem exudate in \u3ci\u3eEucalyptus globulus\u3c/i\u3e LABILLARDIÈRE, 1799 (Myrtaceae)

The structure of the salivary glands of the free-living aphalarid Ctenarytaina eucalypti, which infests multiple species of Eucalyptus in Australasia and has been introduced into many other regions of the world, is described and illustrated. The principal salivary gland is multilobed whereas the accessory gland is tubular. 1-D electrophoresis revealed proteins of approximately 58 and 64 kDa in the salivary gland extracts and proteins of similar molecular weights in the extracted plant exudates, including phloem, from infested leaves and tender shoots of E. globulus. Proteins that could fall within this range include, but are not limited to, glucosemethanol- choline-oxidoreductase (53-66 kDa), Zn-binding dehydrogenase (67 kDa) and esterase (65-96 kDa), in addition to cytochrome P-450 (50-55 kDa), trehalase (56 kDa), amylase (50-75 kDa) and lipase (48-52 kDa). Previous studies indicate that glucose-methanol-cholineoxidoreductase, Zn-binding dehydrogenase, cytochrome P-450 and trehalase suppress plantdefence mechanisms, whereas the cell-degrading enzymes such as amylase, lipase and esterase have a possible role in enabling C. eucalypti to insert its stylet into leaf and shoot tissues of E. globulus