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Plant Protective Proteins

Function of key enzymes that control stomatal defence

In guard cells, the activity of a lipoxygenase contributes to alkylation of a protein kinase and thus causes stomatal closure induced by biotic stresses.

Published on 10 July 2019

In our team, we are also exploring a signaling pathway that contributes to innate immunity of plants. This route involves oxidative stress and in particular, a lipoxygenase present in the guard cells.

   Arabidopsis leaf epiderm (neutral red staining) © Jean-Luc  Montillet

Since guard cells control a significant part of gas exchanges required for photosynthesis, another objective of our scientific project is to understand how physical and biological threats can interfere with this important function in plants. In Arabidopsis, inoculation of the plant leaves with the bacterium Pseudomonas syringae is followed by activation of lipoxygenase 1 (LOX1), present in guard cells. This enzyme is involved in the production of reactive oxylipins that trigger stomatal closure. We are studying this original signaling pathway of the guard cell that prevents penetration of the pathogen and colonization of the plant. A "click chemistry" approach allowed us to identify a serine-threonine protein kinase that plays a crucial role in this signaling pathway. The mechanism by which this protein kinase operates in this defence phenomenon is currently being elucidated.

Contact : Jean-Luc MONTILLET