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RESEARCH PRODUCT

Rôle de la dynamique de la membrane plasmique dans la mise en place des réactions de défense chez le tabac

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The binding of cryptogein, a plant defense elicitor secreted by an oomycete, to an unknown receptor triggers well-known biochemical events of early signal transduction at the plasma membrane of tobacco cells. One of these early events is the transient production of Reactive Oxygen Species (ROS) by an NADPH oxidase, NtrbohD. We were thus interested to analyze the dynamic of the plasma membrane during these early stages. We determined that internalization of the endocytotic marker FM4-64 is stimulated a few minutes after addition of cryptogein to tobacco BY-2 cells. This stimulation is specific to the signal transduction pathway elicited by cryptogein since a lipid transfer protein, which binds to the same receptor as cryptogein but without triggering signaling, does not increase endocytosis. To define the nature of the stimulated endocytosis, we quantified clathrin-coated pits (CCPs) formation on the plasma membrane of BY-2 cells. A transitory stimulation of this morphological event occurs within the first 15 min of cryptogein treatment. The kinetics of this transient increase in CCPs at the plasma membrane coincides with that of ROS production occurring after elicitation. Moreover, in BY-2 cells expressing NtrbohD antisense cDNA, which are unable to produce ROS when treated with cryptogein, the CCP stimulation is inhibited. These results indicate that the endocytic process, a new-described early event induced by cryptogein in tobacco is due, at least partly, to clathrin-mediated endocytosis and is correlated to ROS production by the NADPH oxidase, NtrbohD.