**2. Material and methods**

368 Lipid Metabolism

characterized from wheat [45].

relatively to new findings.

above.

by molecular and biochemical approaches.

and precursors of oxidized lipids are released.

properties, LTPs are thought to be involved in membrane biogenesis and regulation of intracellular FA pools [38]. Many roles were suggested for LTPs: involvement in cutin formation, embryogenesis, symbiosis and adaptation of plants to various environmental conditions [39]. Among them, defensive role of LTPs has been proposed. Indeed, LTPs have been naturally classified as members of pathogenesis-related (PR) proteins belonging to the group PR-14 [40]. Some members of this family have the ability to inhibit the growth of fungal pathogens in barley and maize [41], in sunflower against *Fusarium solani* [42], in transgenic rice against *Magnaporthe grisea*, *Rhizoctonia solani* and *Xanthonomas oryzae* [43]. In transgenic wheat expressing *Ace-AMP,* the corresponding encoded LTP showed enhanced antifungal activity against *Bgt* [44]. *Ltp3F1,* a novel gene encoding an antifungal protein against *Alternaria sp*., *Curcularia lunata*, *Bipolaris oryzae* and *Sarocladium oryzae* was

In this review, we will discuss further and extend the study conducted by Renard-Merlier *et al*. [46], where a global investigation of total FA content in relation to treatment with four inducers of resistance and to powdery mildew infection was undertaken. Previous studies established that lipid metabolism is altered by Milsana®, Iodus 40®, HSA, SA and trehalose [8,10]; therefore, our work aimed to characterize their impact at the total FA level. During a time course experiment, content (quantitative analysis) and percentage (qualitative analysis) of FAs were compared in treated plants and in controls, as well as in non-inoculated (ni) plants and *Bgt*-challenged plants (i). Previous results will be considered and discussed

Moreover, the effect of one resistance inducer, namely SA, on lipid metabolism is evaluated

Phospholipids being the major membrane components, we investigated PC, PE, DAG and PA content variation in wheat leaves infiltrated with salicylic acid (SA). SA can modulate the content variation of these compounds, reservoirs from which biologically active lipids

At the transcriptional level, a PLC-encoding gene expression was investigated in an attempt to assign any participation of this pathway in the phospholipids equilibrium described

We also investigated free FAs and PLFAs content variations in SA-infiltrated wheat leaves; this pool of lipids is quite interesting since it ensures several functions, from being an energy source to acting as cellular messengers; the latter being highly related to resistance induction in plants. The lipoxygenase response to SA-infiltration, at the molecular and enzymatic level, was also evaluated; this enzyme activity is important for oxylipins biosynthesis in

An LTP-encoding gene expression was also monitored, taking into account the possible antifungal activity of LTPs as well as their ability to bind and transport membrane lipids,

plants, because of its position upstream the cascade of enzymatic lipid peroxydation.

thus participating in lipid-mediated signaling mechanisms.

### **2.1. Treatments application**

Wheat (*Triticum aestivum*) cultivar Orvantis was used throughout the experiments. It was provided by Benoit C.C. (Orgerus, France). This cultivar is fully susceptible to the MPEBgt1 powdery mildew isolate. First leaf of ten-day-old wheat plantlets was infiltrated with salicylic acid (1g/L) solution using a hypodermic syringe without needle. Infiltrated area was delineated with a marker pen. Control plantlets were infiltrated with distillated water.

Ten-day-old wheat seedlings were treated with solutions of Iodus 40® (1g/L), HSA (1g/L), Milsana® (0.3% v/v) and trehalose (15g/L) as described by Renard-Merlier *et al*. [46]. Treatments consisted in "up-to-run-off" sprayings. Two days after inducer treatments, seedlings to be inoculated were sprayed with conidia of *Bgt* suspended in Fluorinert FC43 at a concentration of 5.106 spores.mL-1.
