Book of Abstracts - Geyseco

01 - PL - Plenary Sessions Lectures
ago suggested the existence of a repressor of JA responses targeted
by SCF COI1 for degradation by the proteasome in response
to JA. Another important step in the pathway is represented by
the transcription factor MYC2, which regulates several responses
to JA. However, several key questions such as the link between
these two steps in the pathway (MYC2 and SCF COI1 ), the nature
of the bioactive hormone and the identity of its receptor remained
unknown. We have recently identified a novel family of JA-regulated
nuclear targets of SCF COI1 , named JAZ (Jasmonate ZIM-domain
proteins). JAZ proteins are repressors of AtMYC2, linking
the previous known steps in the pathway. Moreover, the identification
of JAZ repressors has also paved the way to identify
the jasmonate receptor (the F-box COI1) and the bioactive form
of the hormone [(+)-7-iso-JA-Ile]. Recently, the identification of
a Novel-Interactor-of-JAZ proteins (NINJA) has uncovered the
mechanism by which JAZ proteins repress MYC2 activity. How
these discoveries help to understand the molecular mechanisms
underlying JA-signalling will be discussed during the seminar.
PL11: FROM PLANT-PATHOGEN INTERACTIONS TO
ECOGENETICS OF PLANT-MICROBE COMMUNITIES
Schulze-Lefert, P.*
Max Plankc Institute for Plant Breeding Research, Köln, Germany
*Corresponding author, e-mail: schlef@mpiz-koeln.mpg.de
Parasitic and symbiotic associations between plants and microbes
are merely the two extreme outcomes of a continuum of
inter-organismal interactions affecting plant productivity. Little
is understood about plant-microbe interactions that are, at first
glance, symptomless. Complex communities of poorly studied
plant-associated microbes are an untapped reservoir that can promote
plant health and productivity. We have begun to examine
the microbiome of the Arabidopsis rhizosphere using T-RFLP
and 454 pyrosequencing profiling methods. I will describe the
structure of root-associated bacterial communities found in natural
soil and our attempts to examine the genetic basis of their
formation.
PL12: MECHANISMS AND PHENOTYPIC CONSE-
QUENCES OF DNA METHYLATION IN ARABIDOPSIS
Colot, V.*
Institut de Biologie de l’Ecole Normale Supérieure (IBENS),
CNRS, Paris, France
*Corresponding author, e-mail: colot@biologie.ens.fr
DNA methylation plays key roles in the control of genome activity
in plants and mammals. It is critical for the stable silencing of
repeat elements and is also involved in the epigenetic regulation
of some genes. Despite similarities in the controlling functions of
DNA methylation, its dynamics and deposition patterns differ in
several respects between plants and mammals. One of the most
striking differences is that plants tend to propagate pre-existing
DNA methylation states across generations, whereas mammals
re-establish them genome wide at every generation. Our recent
findings on the transgenerational stability of DNA methylation
patterns in Arabidopsis will be presented. The role of RNAi in
the incremental methylation and silencing of repeat elements
over successive generations and in the preservation of normal
expression of neighboring genes will be highlighted
PL13: MAKING OIL IN BIOMASS BY REGULATING
FATTY ACID BREAKDOWN AND LIPID SYNTHESIS PA-
THWAYS.
Graham, I; Slocombe, S; He, Z; Dyer, J; Hernandez, L; Larson, TR.
University of York
*Corresponding author, e-mail: iag1@york.ac.uk
Plant oils in the form of triacylglycerol (TAG) are used for food,
industrial feedstock and biofuel manufacture. Although TAG is
typically harvested from the fruit or seeds of oil crop species,
plants can also accumulate small amounts of TAG in the leaves
and other vegetative tissues. Partitioning of fatty acids into TAG
involves several endoplasmic reticulum associated acyltransferases.
We have found that when fatty acid breakdown is blocked
in seedlings of the model plant Arabidopsis, recycling of
fatty acids back into oil body TAG occurs. A soluble cytosolic
acyltransferase appears to be involved in this process. In older
vegetative leaves, we have found that TAG levels can be increased
significantly (10–20 fold) by blocking fatty acid breakdown,
particularly during extended dark treatments or leaf senescence.
Generation of a double mutant in fatty acid breakdown and diacylglycerol
acyltransferase 1 (DGAT1) results in a severe vegetative
growth phenotype suggesting that partitioning of fatty acids
to TAG in leaves is carried out predominantly by this acyltransferase.
Ectopic expression of LEC2, a seed development transcription
factor involved in storage product accumulation results
in accumulation of seed oil type species of TAG in senescing
tissue that are blocked in fatty acid breakdown. Our data suggests
that recycled membrane fatty acids can be re-directed to TAG by
expressing the seed-programme in senescing tissue or by a block
in fatty acid breakdown. This work raises the possibility of producing
significant amounts of oil in vegetative tissues of biomass
crops such as Miscanthus.
PL14: PLANTS RESPONSES TO GLOBAL CHANGE
Valladares, F.*
Instituto Recursos Naturales CSIC
*Corresponding author, e-mail: valladares@ccma.csic.es
Current environmental change is having important impacts on
plant performance. Global change involves not only a general
trend of increasing air temperatures but also an increased frequency
of extreme climatic events, habitat fragmentation and
degradation, and high rates of biotic exchange leading to assemblages
of novel communities of plants, animals and microorganisms.
Plant responses to these changes involve plastic phenotypic
changes (e.g. acclimation), passive tolerance of the increased
stress, rapid microevolutionary changes, and, if all this fails,
local extinctions. There are two main novelties of global change
pressures for plants: the speed of the environmental change
and the fact that it involves changes in several biotic and abiotic
factors simultaneously. While plant stress physiology has promoted
active research, plant physiology under multiple stresses
still requires extensive attention. I illustrate what we know and
what we should know about plant physiology under global change
conditions with examples of Mediterranean ecosystems where
water limitations are exacerbated by climate change. Impacts of
changing water availabilities coupled to changes in the light environment
are mediated by other co-occurring factors such as soil
fertility and air temperature, but also by the presence and performance
of other competing or symbiotic organisms. Co-existing
plants can either facilitate or outcompete the study species and
the stress level imposed by water is profoundly affected by organisms
in the soil.
PL15: MECHANISTIC ANALYSIS OF THE ENDODER-
MIS AS A SELECTIVE AND PROTECTIVE ROOT-SOIL
INTERFACE
Geldner, N.*
University of Lausanne
*Corresponding author, e-mail: Niko.Geldner@unil.ch
We analyse the molecular mechanisms that underlie the development
and function of the root endodermis in Arabidopsis. The endodermis
is a cell layer in the root of all higher plants and thought
to be of central importance for plant nutrition and stress resistance.
We have established molecular markers which demonstrate
that the endodermal plasma membrane has two separate polar
domains of distinct function. Our description of endodermal
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