Involvement of cytokinin response factor 6 in the integration of abiotic stress responses with metabolism and growth in Arabidopsis thaliana.

Abstract

Main conclusion: This review highlights the importance of the CYTOKININ RESPONSE FACTOR 6 transcription factor as a plant regulatory nexus integrating responses to multiple abiotic stresses with metabolism, growth and development. Cytokinin Response Factors constitute a subfamily of plant transcription factors that have been identified as cytokinin-responsive APETALA2/ethylene-responsive element binding proteins and further characterised as components of cytokinin signalling. Besides being involved in the canonical cytokinin signalling pathway, they are part of complex networks of interactive regulation. Their mode of action, their interactions and their functions however remain to be fully understood. Among cytokinin response factors that are currently identified and characterised in Arabidopsis thaliana, CYTOKININ RESPONSE FACTOR 6 has been extensively studied as it is related to numerous developmental, nutritional, hormonal, abiotic stress and biotic stress processes. CYTOKININ RESPONSE FACTOR 6 was thus recently shown to be part of a SNF1-related kinase1/Jumonji C domain-containing JMJ15 regulatory axis involved in energy, oxidative stress and growth co-regulation. This review focusses on involvement of CYTOKININ RESPONSE FACTOR 6 in the integration of abiotic stress responses with metabolism, growth and development, and on the underlying mechanisms of this integration. The characterisation of CYTOKININ RESPONSE FACTOR 6 as a stress-growth nexus will be highlighted in terms of regulatory processes and mechanisms. The essential roles of this stress-growth nexus will be discussed in the context of multiple stresses and global changes with potential implications for plant biodiversity dynamics and agricultural sustainability.