15th International Conference on Arabidopsis Research - TAIR

T07-061
Structure-Function Relationship within the Invertase/
Pectinmethylesterase Inhibitor Family of Arabidopsis
thaliana
Michael Hothorn(1), Sebastian Wolf(2), Steffen Greiner(2), Klaus Scheffzek(1)
1-European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Programme,
Meyerhofstr. 1, 69117 Heidelberg, Germany
2-Heidelberg Institute of Plant Sciences (HIP), Im Neuenheimer Feld 360, D-69120 Heidelberg,
Germany
Upon secretion into the extracellular cell-wall compartment, a variety of plant
enzymes do escape cellular control mechanisms. This lack of direct regulation
appears to be compensated through production of inhibitory proteins. In
particular, these inhibitors seem to be important during processes denoted
by fast metabolic or developmental switches. We are focusing on the analysis
of such an inhibitory protein family acting towards plant acid invertase and
pectin methylesterase (PME). By sequence homology, currently 39 open reading
frames have been assigned to this family, referred to as PMEI-RP (pectin
methylesterase inhibitor related proteins), in Arabidopsis thaliana. Recently,
the biotechnological potential of the PMEI-RPs has been pointed out [1,2].
We have used a structural biology approach to investigate in three dimensions,
how members of this inhibitory family achieve their puzzling specificity
towards apparently unrelated enzymes. Based on several crystal structures of
an invertase inhibitor from tobacco [3] and a pectin methylesterase inhibitor
from Arabidopsis in concert with detailed biochemical analysis we suggest a
novel module within in these proteins to be critical for the inactivation of the
target enzymes. Based on our findings, we will present a model for proteinprotein
interaction based enzyme regulation in the plant cell wall.
[1] Rausch, T. and Greiner, S. (2004) Biochimica et Biophysica Acta 1696, 253-61.
[2] Giovane, A., Servillo, L., Balestrieri, C., Raiola, A., D'Avino, R., Tamburrini, M.,
Ciardiello, M.A. and Camardella, L. (2004) Biochimica et Biophysica Acta 1696, 245-52.
[3] Hothorn, M., D'Angelo, I., JA, M.A., Greiner, S. and Scheffzek, K. (2004) Journal of
Molecular Biology 335, 987-95.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T07-062
QTL analysis of carbohydrates and growth-related
traits in a new recombinant inbred population
derived from the Ler x Kond cross
Mohamed E. El-Lithy(1, 2), Leónie Bentsink(1), José Broekhof(3), Hein van der
Poel(3), Michiel van Eijk(3), Maarten Koornneef(1), Dick Vreugdenhil(2)
1-Laboratory of Genetics, Plant Science department, Wageningen University, Arboretumlaan 4,
6703 BD Wageningen, The Netherlands.
2-Laboratory of Plant Physiology, Plant Science department, Wageningen University, Arboretumlaan
4, 6703 BD Wageningen, The Netherlands
3-Keygene N.V., Agro Business Park 90, P.O. Box 216, 6700 AE Wageningen, The Netherlands.
To study the relation between carbohydrate metabolism, plant growth and flowering
related traits and to unravel the genetic background of these characteristics,
Arabidopsis natural variation was used. Screening of 22 accessions
and 3 mutants (pgm, sex and adg) for their diurnal patterns of carbohydrate
accumulation in leaves, revealed 2 classes: the first one accumulates sugars
(glucose, fructose and sucrose) and starch during the day, while the second
class exhibits a nearly constant level of carbohydrates over the day. Large
variations between these accessions were recorded for dry weight, seed
weight and relative growth rate but not for water content (El-Lithy et al.,
2004). For quantitative trait locus (QTL) analysis, 127 recombinant inbred
lines (RILs) (F9 generation) derived from the cross between Landsberg erecta
(Ler) and Kondara (Kond), were used. These RILs were genotyped using the
SNPWave technique (van Eijk et al., 2004) with the addition of some PCR
markers (microsatelites and INDELs).
RILs were grown on hydroponics solution as well as in the greenhouse. QTLs
for carbohydrates, relative growth rate (RGR), chlorophyll fluorescence, dry
weight, fresh weight, root length, flowering time and other traits related to
flowering could be detected. Co-location of QTLs for different traits was
observed at various locations. These co-locations suggest that these traits
might be controlled by the same gene(s) and thus are pleiotropic, or they
indicate the presence of a number of closely linked genes.
El-Lithy et al. (2004) Plant Physiology, 135, 444-458
van Eijk et al. (2004) Nucleic Acids Research 32 (4):e47
T07 Metabolism (Primary, Secondary, Cross-Talk and Short Distance Metabolite Transport)