Page 216 - PC2019 Program & Proceedings

PLANT CANADA 2019

P5. High temperature and ovule failure in field pea (Pisum sativum L.)
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Osorio, E ; A. Davis; R. Bueckert
University of Saskatchewan

Heat stress during reproductive development is one of the main factors associated with yield reduction of
field pea. Although sexual reproduction of the majority of angiosperms involves both male and female
gametophytes, studies on the female gametophyte under heat stress are scarce. In this research, we aimed
to investigate the effect of high temperature on ovule development following fertilization. Plants from 6
cultivars of field pea grown under 24°C day/18°C night were exposed to four days of heat stress (35°C
day/18°C night) during flowering stage. The ovules at the plants’ first four reproductive nodes were
evaluated by employing clearing and light microscopy. The results indicated that heat stress caused a
significant effect on ovule development mainly by accelerating flower ontogeny. Ovaries, ovules, and
embryo sacs of these flowers had advanced stages; however, internal evaluation of the post-
fertilization components of the embryo sacs revealed highly unequal development between ovules.
Although fertilization of these ovules was not highly affected, many of the ovules displayed zygote,
embryo, and endosperm at variable stages of development within the same ovary. Interestingly, heat
stress increased aborted ovules with embryos sacs displaying signs of embryos at globular and heart stage
on pods at maturity stage. Overall, heat stress seems to cause acceleration of reproductive development of
the plants accompanied by an uneven development of the embryo sacs within nearby ovules.

Evelyn Osorio (evelyn.osorio@usask.ca)

P6. Expression of the RING-type ubiquitin ligase, XBAT35, is regulated by ABA and abiotic stress
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Serio, R. ; Q. Li; A. Schofield; S. Stone
Dalhousie University

The increasing concern of climate changes makes it increasingly important to understand the mechanisms
plants use to tolerate stressful environments. One such mechanism involves the production of hormone
abscisic acid (ABA) in response to abiotic stresses. One function of ABA signaling leads to the activation
of multiple transcription factors, which control the expression of genes required to mitigate the stress
response. ABA signalling is regulated by the ubiquitin proteasome system (UPS), which controls the
abundance of signaling pathway components. The UPS uses three enzymes, E1, E2, and E3, to attach
ubiquitin molecules to selected proteins, which are then degraded by the 26S proteasome. E3s or ubiquitin
ligases are of particular importance as they confer substrate specificity. Our study focuses on
characterizing the role of the RING-type E3, XB3 Ortholog 5 (XBAT35), in response to abiotic stress.
XBAT35 is alternatively spliced producing two isoforms; nuclear localized XBAT35.1 and Golgi-
localized XBAT35.2 (1). During pathogen attack, XBAT35.2 is known to regulate the abundance of
accelerated cell death 11 (ACD11), a cell death inhibitor (1). Here, we provide preliminary evidence for a
potential role for XBAT35.1 and XBAT35.2 in the abiotic stress response. The expression of both
isoforms of XBAT35 and ACD11 were found to be induced by ABA and salt. These results suggest that
XBAT35 and ACD11 function to promote abiotic stress tolerance.

Renata Serio (renata.serio@dal.ca)

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