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Abstract:
Photoperiod, light quality, vernalization and ambient growth temperature are
the four major environmental factors that modulate floral transition in Arabidopsis.
Compared to our understanding of the molecular basis of photoperiodic
and vernalization response, the regulation of floral transition by ambient
growth temperature is still largely at a fledgling stage (1, 2). In an effort to
understand the growth temperature mediated effects on floral transition, we
analyzed the known flowering time mutants and a few wild strains of Arabidopsis
for their flowering responses at varying temperature conditions under
both long and short photoperiods.
Under long day conditions, the effects of temperature were modest and high
genetic correlations were observed between varying temperature conditions
suggesting that the same genetic pathway (possibly the photoperiodic
pathway) may play a predominant role even at different temperatures in long
days. However, under short day conditions, the effects of temperature were
more pronounced. Higher temperatures in short days induced floral transition
(Thermo-floral induction) to a similar extent to that of the photoperiodic floral
induction under lower temperatures. This effect was not mediated through
the photoperiodic pathway since the thermo-floral induction was unaffected
in the constans (co) and gigantea (gi) mutants. Mutants of the autonomous
pathway failed to induce floral transition in response to higher temperature.
However, the floral induction by ambient growth temperature can still be seen
in flc-3 mutants, suggesting that the floral repression under lower temperatures
is not exclusively dependent on FLC.
By analyzing wild strains of Arabidopsis we have identified accessions that
are impaired in thermo-floral induction under short day conditions. We have
also identified accessions that display a temperature specific flowering response
under long day conditions (3). Using both Mendelian and quantitative
genetic approaches we are mapping the genetic loci underlying thermo floral
responses in Arabidopsis thaliana.
