Cyclin-dependent Kinase E1 (CDKE1) Provides a Cellular Switch in Plants between Growth and Stress Responses

Plants must deal effectively with unfavorable growth conditions that necessitate a coordinated response to integrate cellular signals with mitochondrial retrograde signals. A genetic screen was carried out to identify regulators of alternative oxidase ( rao mutants), using AOX1 a expression as a model system to study retrograde signaling in plants. Two independent rao1 mutant alleles identified CDKE1 as a central nuclear component integrating mitochondrial retrograde signals with energy signals under stress. CDKE1 is also necessary for responses to general cellular stresses, such as H 2 O 2 and cold that act, at least in part, via anterograde pathways, and integrates signals from central energy/stress sensing kinase signal transduction pathways within the nucleus. Together, these results place CDKE1 as a central kinase integrating diverse cellular signals and shed light on a mechanism by which plants can effectively switch between growth and stress responses. Background: Mitochondria send signals to the nucleus to modulate gene expression when mitochondrial function is perturbed. Results: Cyclin-dependent kinase E1 (CDKE1) was identified as an essential component in regulation of responses to perturbation of mitochondrial electron transport. Conclusion: Mitochondrial regulation is integrated with growth, energy, and other cellular stress signaling pathways. Significance: The identification of a molecular link between mitochondrial retrograde regulation and growth and stress signaling pathways.