Page 185 - PC2019 Program & Proceedings

PLANT CANADA 2019

S155. Investigating the basis of strigolactone perception by HYPOSENSITIVE TO
LIGHT/KARRIKIN INSENSITIVE 2
2
*2
2
1
2
Toh, S. ; S. Schuetz ; A. Arellano Saab ; H. Al Galib ; P. Stogios ; P. McCourt ; S. Lumba
2
2
1 Meiji University
2 University of Toronto
The HYPOSENSITIVE TO LIGHT/KARRIKIN INSENSITIVE 2 (HTL/KAI2) α/β hydrolases are
known to play a critical role in the life cycle of parasitic plants of the genus Striga. These hydrolases
serve as receptors for strigolactones (SLs), a class of compounds exuded by the roots of many plants.
Upon perception of even minute concentrations of SLs, Striga seeds begin to germinate and parasitize the
host. Striga poses a serious threat to farming in many regions of the developing world, including sub-
Saharan Africa, where two thirds of arable land are estimated to be infested with Striga seeds. For
scientists seeking to develop strategies to combat Striga infestation, the basis of the remarkable sensitivity
of Striga’s SL receptors represents a promising area of study. To this end, we have produced a series of
mutant variants of the Arabidopsis thaliana homolog of HTL/KAI2, which is only weakly responsive to
SL. By substituting certain key amino acids in the protein’s active site, we have created a receptor
conferring heightened Arabidopsis germination under inhibitory conditions, which is further enhanced by
the addition of SL. Additional study of this mutant receptor may offer insight into the biochemical basis
of Striga’s SL sensitivity.

Stefan Schuetz (stefan.schuetz@mail.utoronto.ca)

S156. Arabidopsis clade I TGACG-motif binding basic leucine-zipper transcription factors mediate
BLADE-ON-PETIOLE-dependent activities in development and defense
1
Wang, Y. ; C. Bergin ; B. Salasini ; M. Khan ; B. Devi ; M. Bush ; B. Oyetoran ; M.L. Smith ; R.
1
1
1
1
1
1
*1
1
2
Subramaniam ; S.R. Hepworth
1 Carleton University
2 Agriculture and Agri-Food Canada
Lateral organs formed by the shoot apical meristem (SAM) are separated from surrounding stem cells by
low-growth regions called boundaries. Boundaries also provide axillary meristems and regulate abscission
to determine plant architecture. Arabidopsis thaliana (Arabidopsis) BLADE-ON-
PETIOLE1 and 2 (BOP1/BOP2) represent a class of genes important for boundary patterning in land
plants. Members of this family encode transcriptional co-regulators that interact with TGACG-motif
binding (TGA) basic leucine-zipper (bZIP) transcription factors for recruitment to DNA. Here, we show
that clade I TGA bZIP transcription factors TGA1 and TGA4, previously associated with plant defense,
are essential cofactors in BOP-dependent regulation of plant development. TGA1 and TGA4 are
expressed at organ boundaries and function in the same genetic pathways as BOP1/BOP2 required for
SAM maintenance, flowering, and inflorescence architecture. Further, we show that TGA1/TGA4 form
complexes with BOP1/BOP2 in vivo, contributing to activation of ARABIDOPSIS THALIANA
HOMEOBOX GENE1, which is needed for boundary establishment. Transcript profiling and chromatin
immunoprecipitation assays were used to identify additional co-regulated target genes of TGA1/TGA4
and BOP1/BOP2 involved in plant immunity. This work reveals a role for clade I TGAs at boundaries
and hints at possible additional roles for this module in plant defense.

Ying Wang (yingwang4@cmail.carleton.ca)

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