Following development of belowground sugar beet traits with MagneticResonance Imaging (MRI) and Positron Emission Tomography (PET)

Both structural and functional properties of belowground organs are critical for development and yield of plants, but compared to the shoot, these are much more difficult to observe due to soil opacity. With the yield relevant organ situated belowground sugar beet is even more affected by this difficulty than other crops. The beet shows a complex tissue structure with several cambia active in parallel that are tightly linked with its function in storing photoassimilates in the form of sucrose. Additionally the development of traits during the growth period such as morphology, anatomy, sugar content and photoassimilate allocation within the beet cannot be addressed with destructive sampling techniques. Nevertheless, these are key factors for sugar yield. Here, we show application of Magnetic Resonance imaging (MRI) to investigate on a routine basis the development of structural traits such as beet diameter, biomass and width of cambia rings in plants potted in an agricultural soil mixed with sand. Functional traits such as sugar content and petiole xylem flow velocity were investigated regularly during the same time periods of up to four months. Individual tissues could be identified using MRI T2-maps with the aid of light microscopy at final harvest allowing the study of the development of tissues such as cambia, phloem or storage parenchyma in the cambial rings. Different Genotypes, commercial varieties as well as such of contrasting sugar content from KWS material were compared. For studying photoassimilate allocation we applied Positron Emission Tomography (PET) using carbon isotope 11C as a tracer. We show 3D PET maps of Radioactivity in the beet tracing the routes of photoassimilate translocation from the leaves into the beet. This revealed translocation pattern and their dynamics during three month of growth. These data are further used for fitting simple transport models, to estimate assimilate transport velocity and assimilate storage along the transport pathway in specific sections of the beet. Together these approaches have the potential to yield unique insights into sugar beet belowground development. Thereby they will shed new light on processes like sugar storage or stress responses in the beet

Coagulation of rubber latexes

Coagulated SBR or nitrile rubber latexes with low salt contents, suitable for processing in belt or bar driers, are prepd. by adding mixts. of NaCl and quaternary ammonium polymers to the latexes. Thus, an 18%-solids nitrile rubber latex contg. 0.4 phr poly(dialkyldimethylammonium chloride) (I) requires 50 parts satd. NaCl soln. for complete coagulation of 100 parts latex, compared with 150 in the absence of I. [on SciFinder (R)

Phloem Import and Storage Metabolism Are Highly Coordinated by the Low Oxygen Concentrations within Developing Wheat Seeds

We studied the influence of the internal oxygen concentration in seeds of wheat (Triticum aestivum) on storage metabolism and its relation to phloem import of nutrients. Wheat seeds that were developing at ambient oxygen (21%) were found to be hypoxic (2.1%). Altering the oxygen supply by decreasing or increasing the external oxygen concentration induced parallel changes in the internal oxygen tension. However, the decrease in internal concentration was proportionally less than the reduction in external oxygen. This indicates that decreasing the oxygen supply induces short-term adaptive responses to reduce oxygen consumption of the seeds. When external oxygen was decreased to 8%, internal oxygen decreased to approximately 0.5% leading to a decrease in energy production via respiration. Conversely, increasing the external oxygen concentration above ambient levels increased the oxygen content as well as the energy status of the seeds, indicating that under normal conditions the oxygen supply is strongly limiting for energy metabolism in developing wheat seeds. The intermediate metabolites of seed storage metabolism were not substantially affected when oxygen was either increased or decreased. However, at subambient external oxygen concentrations (8%) the metabolic flux of carbon into starch and protein, measured by injecting (14)C-Suc into the seeds, was reduced by 17% and 32%, respectively, whereas no significant effect was observed at superambient (40%) oxygen. The observed decrease in biosynthetic fluxes to storage compounds is suggested to be part of an adaptive response to reduce energy consumption preventing excessive oxygen consumption when oxygen supply is limited. Phloem transport toward ears exposed to low (8%) oxygen was significantly reduced within 1 h, whereas exposing ears to elevated oxygen (40%) had no significant effect. This contrasts with the situation where the distribution of assimilates has been modified by removing the lower source leaves from the plant, resulting in less assimilates transported to the ear in favor of transport to the lower parts of the plant. Under these conditions, with two strongly competing sinks, elevated oxygen (40%) did lead to a strong increase in phloem transport to the ear. The results show that sink metabolism is affected by the prevailing low oxygen concentrations in developing wheat seeds, determining the import rate of assimilates via the phloem

Xenopus Xlmo4 is a GATA cofactor during ventral mesoderm formation and regulates Ldb1 availability at the dorsal mesoderm and the neural plate

19 páginas, 7 figuras.We have identified and functionally characterized the Xenopus Xlmo4 gene, which encodes a member of the LIM-domain-only protein family. Xlmo4 is activated at gastrula stages in the mesodermal marginal zone probably in response to BMP4 signaling. Soon after, Xlmo4 is downregulated in the dorsal region of the mesoderm. This repression seems to be mediated by organizer-expressed repressors, such as Gsc. Xlmo4 downregulation is necessary for the proper formation of this territory. Increasing Xlmo4 function in this region downregulates Spemman Organizer genes and suppresses dorsal-anterior structures. By binding to Ldb1, Xlmo4 may restrict the availability of this cofactor for transcription factors expressed at the Spemman Organizer. In the ventral mesoderm, Xlmo4 is required to establish the identity of this territory by acting as a positive cofactor of GATA factors. In the neural ectoderm, Xlmo4 expression depends on Xiro homeoprotein activity. In this region, Xlmo4 suppresses differentiation of primary neurons and interferes with gene expression at the Isthmic Organizer, most likely by displacing Ldb1 from active transcription factor complexes required for these processes. Together, our data suggest that Xlmo4 uses distinct mechanisms to participate in different processes during development.Grants from Dirección General de Investigación Científica y Técnica (PB98-0682 and BMC2001-2122 to J.M. and J.L.G.S.), NIH (AR02080 and AR44882 to B.A.), and an institutional grant from Fundación Ramón Areces to the Centro de Biología Molecular Severo Ochoa are acknowledged.Peer reviewe