Cross-talk between mitochondrial function, growth, and stress signalling pathways in plants

Plant mitochondria harbour complex metabolic routes that are interconnected with those of other cell compartments, and changes in mitochondria! function remotely influence processes in different parts of the cell. This implies the existence of signals that convey information about mitochondria! function to the rest of the cell. Increasing evidence indicates that metabolic and redox signals are important for this process, but changes in ion fluxes, protein relocalization, and physical contacts with other organelles are probably also involved. Besides possible direct effects of these signalling molecules on cellular functions, changes in mitochondria! physiology also affect the activity of different signalling pathways that modulate plant growth and stress responses. As a consequence, mitochondria influence the responses to internal and external factors that modify the activity of these pathways and associated biological processes. Acting through the activity of hormonal signalling pathways, mitochondria may also exert remote control over distant organs or plant tissues. In addition, an intimate cross-talk of mitochondria with energy signalling pathways, such as those represented by TARGET OF RAPAMYCIN and SUCROSE NON-FERMENTING1RELATED PROTEIN KINASE 1, can be envisaged. This review discusses available evidence on the role of mitochondria in shaping plant growth and stress responses through various signalling pathways.