Page 186 - PC2019 Program & Proceedings

PLANT CANADA 2019

S157. A role for receptor kinases in regulating compatible pollen responses in the Brassicaceae
stigma
*
Lee, H.K. ; D. Goring
University of Toronto

Brassicaceae flowers have evolved mechanisms to recognize their pollen grains as providing nutrients to
the wrong mating partner would be disadvantageous. The dry stigmas lack surface secretion which
normally enables automatic pollen germination, and this allows the stigma to tightly regulate pollen
acceptance following pollen-stigma contact. The cellular processes in the stigma that facilitate pollen
acceptance are becoming more clearly defined, but the initial upstream signalling components are yet to
be identified. Previous work in the Goring lab identified a set of receptor-like cytoplasmic kinases,
BRASSIKINS (BKNs), as candidate stigmatic signalling proteins in this pathway. We hypothesize that
the BKNs mediate signal transduction by forming a complex with membrane-bound receptor kinases to
facilitate pollen acceptance. To address this hypothesis, the BKNs were used to screen for putative protein
interactors by testing pairwise combinations with kinase domains from stigma-expressed receptor kinases
in the yeast two-hybrid system. Further characterization of the putative interactors identified two distinct
clusters of receptor kinases, and so far, the loss-of-function mutants show mild compatible pollen
response defects. Current work is focused on creating additional mutant combinations and testing whether
these receptor kinases from different Brassicaceae species can rescue the mutant stigma phenotype.
Overall, we aim to better understand how these stigma-expressed receptor kinases facilitate the early
stages of compatible pollen acceptance and whether they represent a conserved signalling module across
the Brassicaceae.

Hyun Kyung Lee (hyunkyung.lee@mail.utoronto.ca)

S158. The E3 ubiquitin ligase XERICO modulates stomatal development in Arabidopsis thaliana
Mohamed, D. ; E. Vonapartis; C. Carianopol; S. Gazzarrini
*
University of Toronto

Plants must alter their developmental module to effectively respond to a host of environmental stresses
for survival. Stomata, which are epidermal pores that control gas and water exchange, are pivotal for
ensuring plant survival and growth under stress. Consequently, stomatal aperture, density and patterning
are tightly regulated by developmental and stress related signals, to ensure optimal gas and water
exchange between plants and their environment. Arabidopsis XERICO (XER) is a putative RING E3
ubiquitin ligase that increases abscisic acid (ABA) levels and promotes drought tolerance when
overexpressed. Analysis of xer T-DNA insertion and CRISPR-Cas9 mutants revealed that XER may
function in regulating stomatal development. Therefore, I hypothesized that XER promotes drought
tolerance by regulating stomatal development and distribution. To understand XER’s role in development
and stress response, a high throughput yeast-two-hybrid (Y2H) screen was conducted against a library of
ABA responsive genes. A glycosyltransferase (GT) implicated in cell wall synthesis was shown to
interact with XER in Y2H and in planta. Subcellular localization studies and phenotypic analysis of T-
DNA insertion lines revealed the localization of the XER-GT interaction and demonstrated that GT also
functions in stomatal development. We propose that XER may regulate stomatal development by
affecting cell wall function, which may influence plant survival under stress.

Deka Mohamed (deka.mohamed@mail.utoronto.ca)

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