Page 161 - PC2019 Program & Proceedings

PLANT CANADA 2019

S107. Characterizing the role of Arabidopsis thaliana RING-type E3 Ligase XBAT35.2 and its
substrates in abiotic stress tolerance
*
Li, Q. ; S. Stone
Dalhousie University

Ubiquitin ligases (or E3s) select specific proteins for ubiquitination, which involves the attachment of one
or more ubiquitin molecules. The major outcome of ubiquitination is breakdown of modified proteins by
the 26S Proteasome. In plants the ubiquitin-proteasome system is required for responses to environmental
stresses such as pathogen, drought, and high salinity. Of interest is XBAT35, a RING-type ubiquitin
ligase, whose transcript is alternatively spliced to produce two isoforms; XBAT35.1 and XBAT35.2.
XBAT35.2, but not XBAT35.1, can promote defense against pathogen attack by mediating the 26S
Proteasomal turnover of Accelerated Cell Death11 (ACD11) . The aim of this study is to determine
1
whether XBAT35.2, and possibly ACD11, is also involved in abiotic stress tolerance. We found that
seedlings overexpressing ACD11 and mutant xbat35-1, which lack expression of both E3 isoforms, are
more tolerant to the inhibitory effects of ABA and salt on germination and early growth. Interestingly,
under mild salt stress, XBAT35.2 abundance significantly decreases, while the level of ACD11 increases
considerably. However, the abundance of ACD11 is reduced when exposed to severe salt stress, and this
decrease is dependent on proteasome activity. The results and others suggest that mild abiotic stress
stabilizes ACD11 through downregulating its negative regulator XBAT35.2, while severe stress may
produce the opposite outcome. Further study is required, but our preliminary results suggest a role for
XBAT35.2 in abiotic stress tolerance.

Qiaomu Li (qm999255@dal.ca)

S108. Overexpression of de novo DNA methyltransferase BdDRM2 alters Brachypodium distachyon
development and abiotic stress response
*
Ouellette, L. ; B.F. Mayer; J-B. Charron
McGill University

DNA methylation is a major epigenetic modification that can alter gene expression. Changes in DNA
methylation are involved in many plant processes including growth, development, stress response and
possibly adaptation. Genome-wide DNA methylation patterns depend on both de novo and maintenance
methylation, as well as passive and active demethylation. DOMAINS REARRANGED
METHYLTRANSFERASE 2 (DRM2) is the primary de novo DNA methyltransferase in plants, however,
its involvement in temperate cereal development and stress response remains unclear. Therefore, to better
understand the role of DRM2 and de novo DNA methylation in modulating gene expression as it relates
to important agronomic outcomes, we have developed independent BdDRM2-overexpression lines of the
model cereal Brachypodium distachyon. Results suggest that BdDRM2 also regulates DNA methylation
and consequently plays a role in development and abiotic stress response in B. distachyon. When
compared to control plants, BdDRM2-overexpression lines exhibit higher global DNA methylation,
abnormal transcriptional responses to abiotic stress and altered vegetative and reproductive growth.
Efforts to characterize the effects of these characteristics on the stress tolerance of the lines are ongoing.
The findings of this research provide insights into cereal abiotic stress responses, breeding for stress-
resistance in a changing climate, and the possibility of epigenome editing.

Luc Ouellette (luc.ouellette@mail.mcgill.ca)

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