Pernisová M., Klíma P., Horák J., Válková M., Malbeck J., Souček P., Reichman P., Hoyerová K., Dubová J., Friml J., Zažímalová E., Hejátko J.
PROCEEDINGS OF THE NAS OF THE USA
106(9):
3609-3614,
2009
Keywords:
PIN expression, two-component signalling, root meristem, auxin maxima
Abstract:
Postembryonic de novo organogenesis represents an important competence evolved in plants that allows their physiological and developmental
adaptation to changing environmental conditions. The
phytohormones auxin and cytokinin (CK) are important regulators of
the developmental fate of pluripotent plant cells. However, the
molecular nature of their interaction(s) in control of plant organogenesis
is largely unknown. Here, we show that CK modulates
auxin-induced organogenesis (AIO) via regulation of the effluxdependent
intercellular auxin distribution. We used the hypocotyl
explants-based in vitro system to study the mechanism underlying de
novo organogenesis. We show that auxin, but not CK, is capable of
triggering organogenesis in hypocotyl explants. The AIO is accompanied
by endogenous CK production and tissue-specific activation of
CK signaling. CK affects differential auxin distribution, and the CKmediated
modulation of organogenesis is simulated by inhibition of
polar auxin transport. CK reduces auxin efflux from cultured tobacco
cells and regulates expression of auxin efflux carriers from the PIN
family in hypocotyl explants. Moreover, endogenous CK levels influence
PIN transcription and are necessary to maintain intercellular
auxin distribution in planta. Based on these findings, we propose a
model in which auxin acts as a trigger of the organogenic processes,
whose output is modulated by the endogenously produced CKs. We
propose that an important mechanism of this CK action is its effect on
auxin distribution via regulation of expression of auxin efflux carriers.
IEB authors: Klára Hoyerová,
Petr Klíma,
Jiří Malbeck,
Eva Zažímalová
Čeština
English