Abstract

Seasonal control of flowering often involves leaf sensing of daylength coupled to time measurement and generation and transport of florigenic signals to the shoot apex. We show that transmitted signals in the grass Lolium temulentum may include gibberellins ( GAs) and the FLOWERING LOCUS T ( FT) gene. Within 2 h of starting a florally inductive long day ( LD), expression of a 20-oxidase GA biosynthetic gene increases in the leaf; its product, GA 20, then increases 5.7-fold versus short day; its substrate, GA 19, decreases equivalently; and a bioactive product, GA 5, increases 4-fold. A link between flowering, LD, GAs, and GA biosynthesis is shown in three ways: ( 1) applied GA 19 became florigenic on exposure to LD; ( 2) expression of LtGA20ox1, an important GA biosynthetic gene, increased in a florally effective LD involving incandescent lamps, but not with noninductive fluorescent lamps; and ( 3) paclobutrazol, an inhibitor of an early step of GA biosynthesis, blocked flowering, but only if applied before the LD. Expression studies of a 2-oxidase catabolic gene showed no changes favoring a GA increase. Thus, the early LD increase in leaf GA 5 biosynthesis, coupled with subsequent doubling in GA 5 content at the shoot apex, provides a substantial trail of evidence for GA 5 as a LD florigen. LD signaling may also involve transport of FT mRNA or protein because expression of LtFT and LtCONSTANS increased rapidly, substantially (> 80-fold for FT), and independently of GA. However, because a LD from fluorescent lamps induced LtFT expression but not flowering, the nature of the light response of FT requires clarification

Published in

Plant Physiology
2006, Volume: 141, number: 2, pages: 498-507
Publisher: AMER SOC PLANT BIOLOGISTS

SLU Authors

• Moritz, Thomas

  • Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Forest Science


Publication identifier

DOI: https://doi.org/10.1104/pp.106.076760

Permanent link to this page (URI)

https://res.slu.se/id/publ/10253