comparing components of co2 assimilation in a variety of willow species
TRANSCRIPT
saline tolerance is conferred in Swiss chard through an effectiveregulation of leaf Na+ uptake and/or compartmentalisation, ahydroponic study was conducted in an environmentally controlledglasshouse at Writtle College. Seedlings of Swiss chard and fodderbeet (B. vulgaris L. subsp. rapacea), used as a comparative control,were transferred to nutrient solution containing 0, 60, 240 and420 mM NaCl (with a controlled Na+ to Ca2+ molar ratio of 15:1). Ionanalysis (Na+, K+ and Ca2+), fresh and dry weight, leaf area, andchlorophyll content were measured in specific leaves in successiveharvests, from seedlings to mature plants. Swiss chard was shown toaccumulate relatively high levels of leaf Na+ at moderate salinitylevels, but displayed high physiological tolerance to this accumula-tion. The extent to which the results contribute to the understandingof the key physiological characteristics of saline tolerant crop types isdiscussed.
Email Address for correspondence: [email protected]
doi:10.1016/j.cbpa.2009.04.608
P5.32Poster Session — Monday 29th June 2009Production of vacuolar cytokinin dehydrogenases from Arabidop-sis thaliana in Pichia pastoris
Marta Kowalska (Palacký University, Department of Biochemistry,Division of Molecular Biology, Šlechtitel 367 11Olomouc), MáriaŠmehilová (Palacký University, Department of Biochemistry, Divisionof Molecular Biology, Šlechtitel 367 11Olomouc), Petr Galuszka(Palacký University, Department of Biochemistry, Division of Mole-cular Biology, Šlechtitel 367 11Olomouc), FrébortIvo Frébort (PalackýUniversity, Department of Biochemistry, Division of MolecularBiology, Šlechtitel 367 11Olomouc)
Vacuolar proteins in plants possess complex signals of low aminoacid sequence homology and what precludes exact understanding oftheir targeting. When producing such proteins in a recombinant yeastsystem, problems may arise from misinterpretation of the signalsequence by the heterologous host. We study the family of sevencytokinin dehydrogenase enzymes (CKX, EC 1.5.99.12) that control themetabolism of plant hormones cytokinins in Arabidopsis thaliana. Twogenes coding for vacuolar cytokinin dehydrogenase enzymes AtCKX1andAtCKX3were chosen for protein overproduction in Pichia pastoris. Inorder to facilitate purification, recombinant proteins were fused withHis-tag domain. The fusion on the C-terminal end of the proteins,however, proved to be useless in affinity purification. Therefore a novelvector was prepared from pGAPZαA by inserting a coding sequence for10× His from pET16b between the α-factor coding sequence and themultiple cloning site. With both studied proteins, the sequence coding
for N-terminal fragment predicted by SignalP 3.0 as a leader peptidewasremoved before cloning into pGAPZαA to obtain secretion from yeastusing the N-terminal α-factor signal sequence. Initial experiments,however, did not lead to secretion of active proteins. More accurateamino acid sequence analysis of AtCKX1 and AtCKX3 revealed thepresence of a region resembling N-terminal sequence-specific vacuolarsorting signal (ssVSS) that typically containsdegenerate signal [N/L]-[P/I/L]-[I/P]-[R/N/S], also called NPIR consensus sequence, and targetsproteins to lytic vacuoles. Only after deleting this motif, active plantvacuolar cytokinin dehydrogenases were obtained in Pichia pastoris.
Email Address for correspondence: [email protected]
doi:10.1016/j.cbpa.2009.04.609
P5.33Poster Session — Monday 29th June 2009Comparing components of CO2 assimilation in a variety of willowspecies
Martin Parry (Rothamsted Research), Szilvia Bencze (RothamstedResearch), Jeremy Guinard (Rothamsted Research), Ian Shield(Rothamsted Research), Angela Karp (Rothamsted Research), JohnAndralojc (Rothamsted Research)
We need to know the extent to which photosynthetic capacityvaries between willow (Salix) genotypes in order to assess thepotential for increasing carbon capture through selection of traitassociated (photosynthetic) QTLs. If sufficient natural variation inphotosynthetic capacity is apparent, then subsequent attempts toidentify the underlying processes and genes may be justified. Thispreliminary work demonstrates the existence of significant variationin photosynthetic capacity (expressed on a leaf area or leaf dry matterbasis) attributable to metabolic and/or anatomical characteristicswithin willow leaves, as distinct from stomatal limitations. We arecurrently attempting to identify metabolic processes which con-tribute to these differences in photosynthetic capacity. The inter-species variation in above ground biomass (leaves+wood) was moreclosely correlated to differences in total leaf area per plant, than inassimilatory capacity per unit leaf area. Nevertheless, the observedvariation in assimilatory capacity per unit leaf area (of between 2 and3-fold) implies that considerable gains in biomass production couldbe achieved by increasing the photosynthetic capacity per unit area inspecies which already produce many leaves.
Email Address for correspondence: [email protected]
doi:10.1016/j.cbpa.2009.04.610
Abstracts / Comparative Biochemistry and Physiology, Part A 153 (2009) S209–S218S218