The plant hormone cytokinin, existing in several molecular forms, is perceived by
membrane-localized histidine kinases. The signal is transduced to transcription factors
of the type-B response regulator family localized in the nucleus by a multi-step histidineaspartate
phosphorelay network employing histidine phosphotransmitters as shuttle
proteins across the nuclear envelope. The type-B response regulators activate a number
of primary response genes, some of which trigger in turn further signaling events and
the expression of secondary response genes. Most genes activated in both rounds of
transcription were identified with high confidence using different transcriptomic toolkits
and meta analyses of multiple individual published datasets. In this review, we attempt to
summarize the existing knowledge about the primary and secondary cytokinin response
genes in order to try connecting gene expression with the multitude of effects that
cytokinin exerts within the plant body and throughout the lifespan of a plant