Page 114 - PC2019 Program & Proceedings

PLANT CANADA 2019

S13. Dimerization of Vitis ICE with Vitis FAMA enables activation via a specific MYC element in
the Vitis CBF4 promoter sequence
Alibabai, L.; A. Edge; M. Rahman; Nassuth, A.
University of Guelph

Basic helix-loop-helix (bHLH) proteins dimerize with other bHLH proteins to form an active
transcription factor complex, whereby different dimers bind to and activate via a specific MYC
(CANNTG) promoter sequence and thus activate a specific regulon. ICE proteins have at least 2
functions: the activation of cold acclimation via the ICE-CBF pathway and the development mature
stomata. ICE proteins are bHLH transcription factors that induce CBF expression but it is not known with
what proteins they dimerize to do so. On the other hand, dimers of ICE with SPCH (speechless), MUTE
and FAMA direct the three sequential steps in stomata development but it is not known which genes these
dimers activate to direct this development. We investigated the dimer formation by Vitis ICE proteins
using agroinfiltration-directed BiFC (Bimolecular fluorescence complementation), competitive BiFC and
re-localization assays, and determined that many dimers can be formed. However, only ICE-FAMA
combinations but not ICE-SPCH or ICE-MUTE combinations were found to activate expression from a
specific MYC element in the Vitis CBF4 promoter. The possible implications for the functions of Vitis
FAMA or Vitis CBF4 will be discussed. This work was made possible due to an NSERC discovery grant
to AN.

Annette Nassuth (anassuth@uoguelph.ca)

S14. Using global metabolomic and transcriptomic analysis to assess heat-shock-response
functionality in the Antarctic alga Chlamydomonas sp. UWO241
1
1
Possmayer, M. ; M. Cvetkovska ; N. Malczewski ; B. Szyszka ; N. Hüner 2
2
2
1 University of Ottawa
UWO
2
The psychrophilic green alga Chlamydomonas sp. UWO241 (hereafter UWO241) has been the subject of
numerous studies, however these have mainly focused on adaptations which facilitate life at low
temperature as opposed to restricting it from moderate ones. Here, we present the results of tandem
experiments examining the changes to the transcriptome and metabolome of this Antarctic alga at steady-
state growth temperatures and following temperature shifts, as compared to the model alga
Chlamydomonas reinhardtii. Both these experimental approaches reveal that UWO241 has a distinctly
more muted response to the temperature shift regime than does C. reinhardtii. This muted response
reflects the inability of UWO241 to adjust its cellular metabolism in ways appropriate to growth at
moderate temperatures. Furthermore, cell viability assays of UWO241 and C. reinhardtii subjected to the
heat shock regimes used in the ‘omics experiments revealed that the mortality of UWO241, but not C.
reinhardtii, was lowest when the heat shock regime was at its most extreme. These results challenge the
notion that the optimal growth temperature for an organism is that at which it grows most quickly. In the
case of UWO241, temperature stress resistance is greatest at the growth temperature eliciting the slowest
growth, thus the optimal temperature for stress resistance differs from the optimal temperature for growth.

Marc Possmayer (mpossmay@uottawa.ca)

Page 112 of 339