Cytokinin response factors integrate auxin and cytokinin pathways for female reproductive organ development

Abstract

The developmental program of the pistil is under the control of both auxin and cytokinin, which crosstalk converges on the regulation of the auxin carrier PIN-FORMED 1 (PIN1). Here we show that in the triple transcription factor mutant cytokinin response factor 2 (crf2) crf3 crf6 both pistil length and ovule number were reduced. PIN1 expression was also lower in the triple mutant and the phenotypes couldn't be rescued by exogenous cytokinin application. pin1 complementation studies using genomic PIN1 constructs showed that the pistil phenotypes were only rescued when the PCRE1 domain, to which CRFs bind, was present. Without this domain, pin mutants resemble the crf2 crf3 crf6 triple mutant, indicating the pivotal role of CRFs in the auxin-cytokinin crosstalk.