Page 110 - PC2019 Program & Proceedings

PLANT CANADA 2019

S5. Functional characterization of gibberellic acid signalling components in Striga hermonthica
*
Wong, C. ; K. Meteleva; H. McIlwraith; A. Caragea; S. Lumba
University of Toronto.

In the sub-Saharan farmlands of Africa, a devastating parasite, Striga hermonthica affects approximately
$300 million worth of crops every year. Striga seeds germinate in response to strigolactones (SLs)
emitted by host roots but do not germinate in response to gibberellic acid (GA). To investigate this
difference between parasitic and non-parasitic plants, we will determine the function of various GA
signalling components from Striga by expressing them in Arabidopsis thaliana. At the molecular level,
the presence of GA causes DELLA proteins to be degraded in order to elicit a GA response. Arabidopsis
has five partially redundant DELLA genes, all of which are additively involved in regulating important
biological processes such as germination, cell expansion, and floral development. Our bioinformatics
analyses revealed multiple DELLA homologues in Striga (ShDELFAs). To characterize the functions of
these homologues, we generated a series of Arabidopsis transgenics over-expressing each ShDELFA. We
found that these homologues are functional in Arabidopsis. One behaves similarly to Arabidopsis
DELLAs, such that it suppresses germination and vegetative growth, and degrades upon the presence of
GA. In contrast, the others showed several unique characteristics, such as resistance in GA-induced
degradation, and no visible suppression in vegetative development. Further study on how the role of GA
impacts Striga germination may contribute to a solution in eradicating Striga infestations.

Cynthia Wong (cynthia.wongcy@gmail.com)

S6. Two hallmarks of plant adaptation viewed through the embryonic lens
Venglat, P.; K. Tanino
University of Saskatchewan

During angiosperm embryogenesis, stem cell niches, viz., the shoot apical meristem (SAM), root apical
meristem (RAM) and the pro-vascular initials are wired differently to their respective differentiation
programs compared to animal embryogenesis where adult stem niches are nested within organs enabling
their homeostasis. This plant-specific embryonic body plan facilitates an iterative process of
differentiating shoot (phytomer) and root modules thus elaborating the plant body over time and
providing an adaptive advantage. This iterative process, the first hallmark of plant adaptation, is
developmentally timed and environmentally regulated giving rise to diverse architectures that is suited to
their respective habitats. The second hallmark of plant adaptation is the regenerative potential, expressed
as a greater degree of plasticity of their cells and tissues with regards to cell fate when compared to the
animals. A wide range of plant tissues can reprogram their morphogenetic state and regenerate embryos,
shoots and roots. These two hallmarks are generally viewed as two different genetic expressions of plant
development. Using the genetic and molecular data from Arabidopsis embryogenesis that has been
dissected and studied extensively, we present a model that explains the modular nature of development
inherent in the plant embryonic body plan in the context of plant regenerative potential that transitions
from totipotency to a gradient of reprogrammable pluripotent states.

Prakash Venglat (prakash.venglat@gmail.com)

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