Book of Abstracts - Geyseco

FESPB 2010 - XVII Congress of the Federation of European Societies of Plant Biology
Progesterone 5β-reductase (P5βR) catalyzes the 5β-reduction of
progesterone to 5β-pregnan-3,20-dione, and is considered the
first committed step in the branch pathway leading to cardenolides
(1), plant metabolites widely used in patients with compromised
cardiac function. ere we describe the characterization of a
new clone, designated P5βR2.
A database search revealed no significant homology to other
proteins than those corresponding to P5βR. P5βR is conserved
throughout the plant kingdom (1) whereas P5βR2 is restricted
to some species. Like P5βR, the recombinant form of P5βR2
can catalyze the reduction of several steroids with a 3-oxo,Δ 4,5
structure; the highest substrate specificity was obtained with progesterone
(3).
A primary structural analysis of the P5βR2 protein revealed the
presence of several conserved sequences of the short chain dehydrogenases/reductases
(SDR) as well as the novel motifs specific
for a new family represented by P5βR as a prototype (1). A
structural model of P5βR2 and a feasible reaction mechanism of
this protein are depicted. A functional subdivision of the SDR superfamily
has been recently established (2). P5βR family belongs
to a different type of SDRs distinguished by sequence patterns at
the active site region; we propose to be named “Restricted SDR
type”, and according to (2) the family designation is SDR75R
(3). Finally, a comparative structural analysis has been carried
out by means of Molecular Dynamics simulations on the holo
form (including the substrate progesterone and the cofactor NA-
DPH) of P5βR and P5βR2.
1. Gavidia I et al. Phytochemistry 2007, 68: 853-864.
2. Persson B et al. Chem Biol Interact 2009, 178: 94-98.
3. Pérez-Bermúdez P et al. New Phytol 2010, 185: 687-700
S14-001: PRINCIPAL FACTORS CONTROLLING GRE-
ENHOUSE FLUXES IN EVERGREEN OAK FOREST OF
SOUTHERN PORTUGAL
Shvaleva, A.* - Lobo do Vale, R. - Cruz, C. - Castaldi, S. - Rosa,
A.P. - Chaves, M.M. - Pereira, J.S.
Instituto de Tecnologia Quimica e Biologica, Universidade Nova
de Lisboa, Oeiras, Portugal
*Corresponding author e-mail: shvaleva@itqb.unl.pt
Soil water content, soil temperature, pH, ammonium and nitrate
concentrations were studied over one year in an evergreen oak
forest to examine the principal factors controlling greenhouse
gases (GHGs) emission, namely CO 2
, CH 4
and N 2
O fluxes in
Mediterranean-type ecosystems of southern Portugal.
To characterize the seasonal variations in gas fluxes and to
examine the effect of treatments, i. e. simulated rainfall (wateraddition)
and rain-fall exclusion on GHG fluxes, a static chamber
technique was used.
Although we did not detect statistically significant effect of
treatments, our results showed that soil moisture and soil temperature
are important variables controlling soil CO 2
fluxes in
Mediterranean forest ecosystems.
Soil respiration (CO 2
fluxes) showed a strong increase from
summer to autumn. This must be the “Birch effect”, which describes
increases in soil heterotrophic respiration as a result of
stimulation of microbial activity and of structural alterations in
soil micro- and macro-aggregates following autumn rains. Our
results also showed that the soil was a consistent CH 4
sink independently
of the soil water content in the range between 6-20%,
and supported the concept that seasonally dry ecosystems (Mediterranean)
are a significant sink of atmospheric CH 4
.
We hypothesized that in evergreen-forest ecosystems of southern
Portugal the biological oxidation of atmospheric CH 4
takes place
by methanotrophic microorganisms in presence of low soil ammonium
and nitrate contents.
S14-002: WHERE HAS ALL THE CARBON GONE? SEA-
SONAL AND NUTRIENT EFFECTS ON CARBON ALLO-
CATION IN SCOTS PINE
Campbell, C. ¹* - Keel, S.² - Metcalfe, D.³ - Högberg, M. N.³ -
Linder, S.³ - Högberg, P.³ - Nasholm, T.³ - Hurry, V.4
¹SLU
²Princeton University
³Swedish University of Agricultural Research
4
Umeå University
*Corresponding author e-mail: catherine.campbell@plantphys.umu.se
It is becoming increasingly essential that we understand the carbon
balance of whole ecosystems. Nutrient uptake and mycorrhizal
symbionts are a significant carbon sink in the field, and
carbon flux is highly seasonal, making field trials an essential
component in understanding the global carbon balance.
Elevated CO 2
may increase overall carbon uptake, but environmental
and developmental factors will determine the allocation
and thus ultimate fate of that carbon. Using a 13 C pulse-chase
labelling technique, we determined the flow of carbon through
intact stands of fertilized and unfertilized Pinus sylvestris. We
compared carbon allocation early (June) and late (August) in the
growing season, and made a comparison of allocation in fertilised
and unfertilised plots.
Carbon allocation belowground was very low early in the
growing season, when most carbon was allocated to growing
shoots, and much higher near the end of the season. This late
season belowground allocation was greatly reduced by one year
of nitrogen fertilization.
Overall carbon uptake was increased by the fertilization
treatment, so reduced allocation to roots resulted in a very large
fraction of carbon remaining aboveground, in wood and storage
to support growth in early spring. This reduction in belowground
allocation may mean a reduction in carbon sequestration in belowground
biomass and soils under nitrogen deposition, while
forest growth and wood production are increased.
S14-003: THE ROLE OF C “MANAGEMENT” ON RES-
PONSIVENESS OF SHRUBS AT THE NEVADA DESERT
FACE FACILITY
Aranjuelo, I.¹* - Clark, NM.² - Ebbets, A.L.³ - Evans, R.D. - Smith,
S.D.³ - Nogués, S.¹ - Nowak, RS.²
¹University od Barcelona
²Department of Natural Resources and Environmental Science,
University of Nevada Reno, USA
³ School of Life Sciences, University of Nevada Las Vegas, Las
Vegas Nevada, USA
4
School of Biological Sciences, Washington State University, USA
*Corresponding author e-mail: iaranjuelo@yahoo.es
The effect of environmental growth conditions on C source/sink
balance of two desert shrubs (Larrea tridentata and Ambrosia
dumosa) exposed to elevated [CO 2
] (average 521 μmol mol-1
versus average ambient [CO 2
] of 376 μmol mol- 1) was examined
at the undisturbed Nevada Desert FACE Facility (NDFF).
We took advantage of differences in isotopic 13C/12C composition
(δ 13 C) of air above elevated CO 2
plots (δ 13 C ca -18.2‰)
versus that above ambient plots (ca. - 8.0‰) to investigate C
allocation and partitioning. C labeling analyses confirmed that
during the summer dry season, decreases in leaf photoassimilate
accumulation could have been caused by the translocation (especially
in Ambrosia) of C compounds from leaves to roots (and
probably main stems).
Total soluble protein and N concentration data suggest that the
lack of elevated [CO 2
] stimulation of photosynthetic activity
during the primary spring growing season was explained by the
depletion of protein content in elevated [CO 2
] treatments, which
was a result of carbohydrate build-up and a reallocation of nitrogen
away from leaves to other processes more limiting for
growth.
The fact that environmental conditions (drought and elevated
temperature) during the summer decreased photosynthetic activity
and induced the senescence of leaves in the deciduous Ambro-