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SUMMARY:Dynamic regulation of gibberellin gradients influencing plant grow
 th patterning - Alexander Jones\, SLCU
DTSTART:20170216T130000Z
DTEND:20170216T140000Z
UID:TALK70121@talks.cam.ac.uk
CONTACT:38889
DESCRIPTION:The phytohormone gibberellin (GA) is a key regulator of plant 
 growth and development. An ensemble of enzymatic and transport steps contr
 ol the cellular distribution of GA and these steps are themselves influenc
 ed by myriad endogenous and exogenous signals. Although the upstream regul
 ation and downstream responses to GA vary across cells and tissues\, devel
 opmental stages\, and environmental conditions\, the spatiotemporal distri
 bution of gibberellin in vivo remains unclear. We engineered a high-affini
 ty optogenetic biosensor\, Gibberellin Perception Sensor 1 (GPS1)\, that s
 enses nanomolar levels of bioactive gibberellins (Kd = 24 nM for GA4). Ara
 bidopsis thaliana plants expressing a nuclear localised GPS1 report on gib
 berellins at the cellular level. In rapidly elongating tissues in which GA
  promotes rapid cell elongation (i. e. root tips and dark-grown hypocotyls
 )\, GA levels correlated with cell length resulting in longitudinal gradie
 nts of GA in these organs. In roots\, exogenous GA accumulation was also c
 orrelated with cell length\, suggesting that a root GA distribution gradie
 nt can be generated independent of GA biosynthesis. In hypocotyls\, GA lev
 els were reduced in a phytochrome interacting factor (PIF) quadruple mutan
 t in the dark and increased in a phytochrome double mutant in the light\, 
 suggesting that PIFs elevate GA in the dark and that phytochrome inhibitio
 n of PIFs lowers GA levels in the light. This result is in marked contrast
  to regulation of GA in seeds\, where PIFs lower GA levels in the dark and
  phytochrome inhibition of PIFs elevates GA in the light. Better knowledge
  of cellular GA distributions and how they are determinedwill enable a dee
 per understanding of the signal integration upstream and growth programmin
 g downstream of GA\, a small\, mobile signalling molecule with substantial
  influence over plant growth and development.
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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