Physiological Roles of Plant Methionine Sulfoxide Reductases in Redox Homeostasis and Signaling
Résumé
Oxidation of methionine (Met) leads to the formation of two S- and R-diastereoisomers
of Met sulfoxide (MetO) that are reduced back to Met by methionine sulfoxide reductases (MSRs),
A and B, respectively. Here, we review the current knowledge about the physiological functions
of plant MSRs in relation with subcellular and tissue distribution, expression patterns, mutant
phenotypes, and possible targets. The data gained from modified lines of plant models and crop
species indicate that MSRs play protective roles upon abiotic and biotic environmental constraints.
They also participate in the control of the ageing process, as shown in seeds subjected to adverse
conditions. Significant advances were achieved towards understanding how MSRs could fulfil these
functions via the identification of partners among Met-rich or MetO-containing proteins, notably by
using redox proteomic approaches. In addition to a global protective role against oxidative damage
in proteins, plant MSRs could specifically preserve the activity of stress responsive effectors such
as glutathione-S-transferases and chaperones. Moreover, several lines of evidence indicate that
MSRs fulfil key signaling roles via interplays with Ca$^{2+}$- and phosphorylation-dependent cascades,
thus transmitting ROS-related information in transduction pathways.
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