Influence of hydraulic conditions over dunes on the distribution of the benthic macroinvertebrates in a large sand bed river

This study aims to relate the flow structure over mobile dunes recorded on the channel bed of the Paraná River (Argentina) with the spatial distribution of the benthic macroinvertebrates. The following main conclusions have been obtained: (1) the dunes found in the active channel could be considered as hydraulic biotopes at a mesohabitat scale: the bed forms in the thalweg region are subjected to higher shear stresses with low benthic densities; (2) differences in benthic densities were also recorded at within-dunes microhabitat scales: the largest densities were found in the dune troughs where small bed shear stresses occur and minimum densities on the low stoss side of dunes where turbulent agitation near the bottom strongly disturb the bed particles; (3) superimposed dunes on larger dunes may be considered as another microhabitat of still smaller dimensions. Summarizing, multiscale approaches are needed if a comprehensive understanding linking hydrodynamics and morphodynamics processes with benthic ecology is intended.Fil: Amsler, Mario Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Blettler, Martin Cesar Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Ezcurra, Ines Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentin

Suppression of xylan endotransglycosylase PtxtXyn10A affects cellulose microfibril angle in secondary wall in aspen wood.

Certain xylanases from family GH10 are highly expressed during secondary wall deposition, but their function is unknown. We carried out functional analyses of the secondary-wall specific PtxtXyn10A in hybrid aspen (Populus tremula × tremuloides). PtxtXyn10A function was analysed by expression studies, overexpression in Arabidopsis protoplasts and by downregulation in aspen. PtxtXyn10A overexpression in Arabidopsis protoplasts resulted in increased xylan endotransglycosylation rather than hydrolysis. In aspen, the enzyme was found to be proteolytically processed to a 68 kDa peptide and residing in cell walls. Its downregulation resulted in a corresponding decrease in xylan endotransglycosylase activity and no change in xylanase activity. This did not alter xylan molecular weight or its branching pattern but affected the cellulose-microfibril angle in wood fibres, increased primary growth (stem elongation, leaf formation and enlargement) and reduced the tendency to form tension wood. Transcriptomes of transgenic plants showed downregulation of tension wood related genes and changes in stress-responsive genes. The data indicate that PtxtXyn10A acts as a xylan endotransglycosylase and its main function is to release tensional stresses arising during secondary wall deposition. Furthermore, they suggest that regulation of stresses in secondary walls plays a vital role in plant development.Formas (including HemiPop and FuncFiber), Swedish Research Council (VR), Swedish Governmental Agency for Innovation Systems (VINNOVA), Swedish Center for Biomimetic Fiber Engineering (funded by the Knut & Alice Wallenberg Foundation and the Foundation for Strategic Research), European projects EDEN (QLK5-CT-2001-00443) and RENEWALL, FORE, Bio4Energy, Wood Ultrastructure Research Centre, SamNordisk Skogsforskning (project no. 107), Japan Society for the Promotion of Science (JSPS KAKENHI Grant Number 24580243) and the Academy of Finland (1127759).This is the accepted manuscript. The final version is available at http://onlinelibrary.wiley.com/doi/10.1111/nph.13099/abstract

Downregulation of RWA genes in hybrid aspen affects xylan acetylation and wood saccharification

High acetylation of angiosperm wood hinders its conversion to sugars by glycoside hydrolases, subsequent ethanol fermentation and (hence) its use for biofuel production. We studied the REDUCED WALL ACETYLATION (RWA) gene family of the hardwood model Populus to evaluate its potential for improving saccharification. The family has two clades, AB and CD, containing two genes each. All four genes are expressed in developing wood but only RWA-A and -B are activated by master switches of the secondary cell wall PtNST1 and PtMYB21. Histochemical analysis of promoter:: GUS lines in hybrid aspen (Populus tremula x tremuloides) showed activation of RWA-A and -B promoters in the secondary wall formation zone, while RWA-C and -D promoter activity was diffuse. Ectopic downregulation of either clade reduced wood xylan and xyloglucan acetylation. Suppressing both clades simultaneously using the wood-specific promoter reduced wood acetylation by 25% and decreased acetylation at position 2 of Xylp in the dimethyl sulfoxide-extracted xylan. This did not affect plant growth but decreased xylose and increased glucose contents in the noncellulosic monosaccharide fraction, and increased glucose and xylose yields of wood enzymatic hydrolysis without pretreatment. Both RWA clades regulate wood xylan acetylation in aspen and are promising targets to improve wood saccharification.Peer reviewe

Environmental factors restrict the invasion process of

The golden mussel Limnoperna fortunei was introduced into Argentina in 1991 and has since been spreading through the Plata and Guaíba basins at a rate of 240 km.year−1. To assess their ability to invade the Andean tributaries of the Plata Basin (Pilcomayo, Bermejo and Salado del Norte rivers), their current range was assessed and related to the abiotic parameters of sites where they were present and absent. These data were then compared with their known tolerances to identify possible barriers to invasion. Outputs suggested that three environmental parameters are barriers to invasion: salinity and river flow intermittence in different sectors of the rivers Pilcomayo and Salado del Norte, and concentration of suspended sediments in the Bermejo River and in the upper reaches of the Salado del Norte and Pilcomayo rivers. The importance of these findings is discussed in relation to using environmental data to infer the invasion possibilities and the utility of environmental data to better understand invasion patterns and processes

Overexpression of PaNAC03, a stress induced NAC gene family transcription factor in Norway spruce leads to reduced flavonol biosynthesis and aberrant embryo development

Abstract Background The NAC family of transcription factors is one of the largest gene families of transcription factors in plants and the conifer NAC gene family is at least as large, or possibly larger, as in Arabidopsis . These transcription factors control both developmental and stress induced processes in plants. Yet, conifer NACs controlling stress induced processes has received relatively little attention. This study investigates NAC family transcription factors involved in the responses to the pathogen Heterobasidion annosum (Fr.) Bref. sensu lato. Results The phylogeny and domain structure in the NAC proteins can be used to organize functional specificities, several well characterized stress-related NAC proteins are found in III-3 in Arabidopsis (Jensen et al. Biochem J 426:183\u2013196, 2010). The Norway spruce genome contain seven genes with similarity to subgroup III-3 NACs. Based on the expression pattern PaNAC03 was selected for detailed analyses. Norway spruce lines overexpressing PaNAC03 exhibited aberrant embryo development in response to maturation initiation and 482 misregulated genes were identified in proliferating cultures. Three key genes in the flavonoid biosynthesis pathway: a CHS, a F3\u2019H and PaLAR3 were consistently down regulated in the overexpression lines . In accordance, the overexpression lines showed reduced levels of specific flavonoids, suggesting that PaNAC03 act as a repressor of this pathway, possibly by directly interacting with the promoter of the repressed genes. However, transactivation studies of Pa NAC03 and PaLAR3 in Nicotiana benthamiana showed that Pa NAC03 activated PaLAR3A, suggesting that PaNAC03 does not act as an independent negative regulator of flavan-3-ol production through direct interaction with the target flavonoid biosynthetic genes. Conclusions PaNAC03 and its orthologs form a sister group to well characterized stress-related angiosperm NAC genes and at least PaNAC03 is responsive to biotic stress and appear to act in the control of defence associated secondary metabolite production

Biochemical characterization of family 43 glycosyltransferases in the Populus xylem: challenges and prospects

Wood formation is a biological process of great economical importance. Genes active during the secondary cell wall formation of wood fibers from Populus tremulaxtremuloides were previously identified by expression profiling through microarray analyses. A number of these genes encode glycosyltransferases (GTs) with unknown substrate specificities. Here we report heterologous expression of one of these enzymes, PttGT43A, a putative IRREGULAR XYLEM9 (IRX9) homologue. Expression trials in Pichia pastoris and insect cells revealed very low levels of accumulation of immunoreactive PttGT43A, whereas transient expression in Nicotiana benthamiana leaves by Agrobacterium infiltration (agroinfiltration) using a viral vector produced substantial amounts of protein that mostly precipitated in the crude pellet. Agroinfiltration induced weak endogenous xylosyltransferase activity in microsomal extracts, and transient PttGT43A expression further increased this activity, albeit only to low levels. PttGT43A may be inactive as an individual subunit, requiring complex formation with unknown partners to display enzymatic activity. Our results suggest that transient co-expression in leaves of candidate subunit GTs may provide a viable approach for formation of an active xylan xylosyltransferase enzymatic complex

Morphological-behavioral adaptations of two benthic invertebrate species to face strong bed hydrodynamic forces in a large South-American river

This scientific communication describes and discusses morphological–behavioral adaptations to flow of two benthic invertebrate species to survive in highly turbulent habitats of the large Paraguay River (Argentina – Paraguay). It is based on field and laboratory observations under microscope made during the performance of usual researches. In this sense, we found that Djalmabatista sp. 1 (Chironomidae, Tanypodinae) ballasts its body by ingestion of fine sediment grains which storage into a dorsal bulge, herein called “dorsal bag”. This specie would have the ability to take or release these grains according to the surrounding hydrodynamic conditions. Otherwise, the juvenile stage of Limnoperna fortunei (Bivalvia, Mytilidae) also ballasts its body but attaching sand grains through the byssal threads.Fil: Blettler, Martin Cesar Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Eberle Folmer, Eliana Gisel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Bullo Rodrigo, Juan Manuel. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias; ArgentinaFil: Ezcurra, Ines Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Amsler, Mario Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentin