4/2012
vol. 93
abstract:
REVIEW PAPER New insights into the signaling and function
of cytokinins in higher plants
BioTechnologia vol. 93(4) C pp. 400-413 C 2012
Online publish date: 2014/10/28
PlumX metrics:
Phytohormones (plant hormones) play a role in the regulation of cellular activities including cell division, elongation
and differentiation, pattern formation, organogenesis, reproduction, sex determination, and responses to
abiotic and biotic stress. The phytohormonal signal transduction pathways operate via cytokinin perception by
transmembrane receptors consisting of two domains: an extracellular domain responsible for hormone binding
and an intracellular domain, sensory His / Asp kinase (HK). Upon phytohormone binding, the receptor undergoes
a conformational change which activates its protein kinase activity. The phosphorylated intracellular domain transfers
the phosphoryl group to the His residue of the histidine phosphotransfer protein (HPt) which in turn phosphorylates
Asp residue in the Response Regulator (RR). The phosphorylated RR protein acts as either a positive
or negative transcription factor that interacts with the gene promoter or other target protein. The two-component
signaling pathway, operating through the His-Asp phosphorelay, controls many physiological and developmental
processes throughout the plant lifecycle (from seed-to-seed). Downstream plant hormone signaling also includes
proteolysis of transcriptional regulators that block the activity of transcription factors. Two-component signaling
operates more frequently in higher plants. Five classic plant hormones had been discovered by the middle of the
twentieth century: auxins, cytokinins, gibberellins, ethylene and abscisic acid. The more recently characterized
hormones include brassinosteroids, strigolactones, jasmonates and salicylates. Considering the tremendous work
that has been undertaken during the last decades, in this review we decided to concentrate on cytokinin signaling
in various plant developmental processes, including responses to biotic and abiotic stresses.
keywords:
signal transduction, cytokinin, phytohormone, cytokinin receptor, histidine-aspartate phosphorelay,
two-component relay system, legume plants, symbiosis
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