Abstract
AbstractMultistep phosphorelay (MSP) signaling integrates hormonal and environmental signals to control plant development and adaptive responses. The type-ARESPONSE REGULATORs(RRAs), the downstream members of the MSP cascade and cytokinin primary response genes, are supposed to mediate primarily the negative feedback regulation of (cytokinin-induced) MSP signaling. However, the transcriptional data suggest the involvement ofRRAsin stress-related responses as well. By employing evolutionary conservation with the well-characterizedArabidopsis thaliana RRAs, we identified 5 and 38 novel putativeRRAsinBrassica oleraceaandBrassica napus, respectively. Our phylogenetic analysis suggests the existence of gene-specific selective pressure, maintaining the homologs ofARR3, ARR6,andARR16as singletons during the evolution ofBrassica oleraceaandBrassica rapa. We categorizedRRAsbased on the kinetics of their cytokinin-mediated upregulation and observed both similarities and specificities in this type of response across Brassicaceae. Using bioinformatic analysis and experimental data demonstrating the cytokinin responsiveness ofArabidopsis-derivedTCSv2reporter, we unveil the mechanistic conservation of cytokinin-mediated upregulation ofRRAsinBrassica rapaandBrassica napus. Notably, we identify partial cytokinin dependency of cold stress-inducedRRAtranscription, thus corroborating the role of cytokinin signaling in the crop adaptive responses.HighlightsWe identifiedBrassicahomologs ofArabidopsistype-A response regulators (RRAs), demonstrate existence of selective pressure preventing severalRRAsmultiplication during Brassicaceae evolution and describe cytokinin dependency of cold-inducedRRAsupregulation.
Publisher
Cold Spring Harbor Laboratory
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