75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

269 A Genetic Analysis of Oxylipin Roles in Cell Survival
Laurent Mene-Saffrane, Stephanie Stolz, Edward Farmer
University of Lausanne
Numerous genetic studies have confirmed the importance of the canonical jasmonate pathway in plant defense.
However linolenic acid (18:3), the source of jasmonates, can be converted in vivo into many other oxylipins. Many of
these are made enzymatically, but non-enzymatic oxidation of 18:3 is known to occur in vivo even in healthy tissues.
Normally, non-enzymatic lipid oxidation is tightly managed by the cell but in some circumstances there is loss of control
over the process. This can occur in some severe stresses and in some pathosystems where the production of excess
reactive oxygen species (ROS) can lead to the oxidative damage. 18:3 oxidation generates of a large spectum of molecules
many of which are regarded as molecular junk and for which biological roles have not been investigated. Among these
molecules are many 'reactive electrophile species' (RES), molecules potentially capable of affecting gene expression in
the host (and pathogen). To investigate the roles of 18:3 and its products in cell survival we first combined lesion mimic
mutants with plants lacking the ability to produce all jasmonates. In parallel, we investigated the effects of 18:3 removal
from lesion mimic mutants. These plants displayed very different phenotypes to those lacking jasmonates with greatly
accelerated lesion development. 18:3 itself or products from this molecule strongly retard lesion formation in the absence
of jasmonates. The results suggest that oxylipin signaling extends to molecules outside the jasmonate family and that
multiple 18:3-derived compounds may play signaling roles in severe stress.
270 Fungal pathogens of man are also pathogens of Arabidopsis
Ines Arrieta-Aguirre, Francisco Fierro Fierro, Enrique Ritter, Susana Garcia-Sanchez
NEIKER
Candida genus of fungi comprise significant pathogens of man. Candida albicans is responsible for most opportunistic
infections in immuno-compromised patients (AIDS or cancer-treated patients). The related species C. glabrata, C.
tropicalis or C. dublinensis are emerging pathogens that are transmitted as nosocomial agents in hospitals. Interestingly
these fungi were first isolated in soil samples, and it is only recently that their importance as human pathogens is being
reported. Since plants are in constant and intimate contact with soil-borne microbes they have evolve several defence
mechanisms that could be useful in the fight against potential, ubiquitously-distributed pathogens. These include the
production of antibiotic substances, the recognition and neutralisation of microorganisms in specialises structures, or the
development of mutuality relationships with microbia.
Here we used the plant Arabidopsis thaliana as a model host for studying Candida infections. Plants were grown
in liquid medium at 30ºC and inoculated with 10 different species of Candida isolated from human hosts. C. tropicalis,
C. kefyr, C. parapsilopsis and Issatchenkia occidentalis produced severe disease symptoms 2 days post-infection, with
plants showing chlorosis, tissue degeneration and a increase of fungal planktonic growth in the medium. In contrast,
C. albicans CAI4, Scedosporium prolificans and C. lusitanicae did not cause severe damage to he plants and did not
increased planktonic growth, but formed a well-developed biofilm on the plat roots. Thus the ability to establish biofilms
on the root surface correlates with the survival of the plant, as a reminiscence of mycorizal formation. To study the
Arabidopsis response to these fungi, a strategy for high-throughput screening of plant proteins able to bind fungal cells
is discussed.