Hormonal networks involved in apical hook development in darkness and their response to light

MAZZELLA, MARIA AGUSTINA; CASAL, JORGE; MUSCHIETTI, JORGE; FOX, ROMINA

Frontiers Plant Science

Frontiers

Año: 2014 vol. 5 p. 1 - 11

In darkness, the shoot of dicot seedlings produces an apical hook as result of differential cell division and extension at opposite sides of the stem. This hook protects the apical meristem from soil-induced mechanical damage. In darkness, gibberellins and ethylene act in concert to promote the asymmetric auxin accumulation required for apical hook formation and maintenance, by affecting auxin synthesis, transport and sensitivity. DELLA proteins are key players downstream gibberellins and HOOKLESS 1 (HLS1) is a central regulator downstream gibberellins and ethylene pathways. PHYTOCHROME INTERACTING FACTORs (PIFs) and CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) are required for hook formation in darkness but their points of action in this response are only partially elucidated. Upon emergence from the soil, light perception by phytochromes and cryptochromes reduces the activity of PIFs and COP1 triggering hook opening as a component of the switch between heterotrophic and photoautotrophic development. Apical hook opening is a suitable model to study the convergence of endogenous and exogenous signals on the control of cell division and cell growth.