Characterization of a putative Triticum aestivum abscisic acid receptor and its role in fungal pathogen resistance
Abscisic acid (ABA) has been well defined as an important stress hormone in plants. The signaling pathway of ABA involves a family of pyrabactin resistant-like-1 PYR/PYL/RCAR receptors (PYL receptors) that bind ABA and form a complex with a protein phosphatase 2C (PP2C) family member resulting in downstream signaling events. The ABA receptor family has been well characterized in the model dicot Arabidopsis thaliana and more recently this characterization has branched out into cereals Oryza sativa (rice) and Hordeum vulgare (barley), as well as the monocot model plant Brachypodium distachyon and Fragaria vesca (strawberry). The analysis of these characterized ABA receptors and the use of online databases has allowed the identification of multiple putative ABA receptors in Triticum aestivum (wheat). ABA has been historically called a positive effector. Overexpression of proteins in the ABA signalling pathway or exogenous application of ABA is known to cause an increase in drought, cold, and salt tolerance. More recently ABA has been linked to increased fungal susceptibility in several plants. The role ABA plays in the biotic stress response is still largely unexplored. The focus of this project was to identify and characterize a putative wheat ABA receptor through bioinformatics and an in vitro enzyme activity assay, and use virus induced gene silencing (VIGS) to test what role this receptor plays in fugal susceptibility. A total of 13 putative ABA receptors were located, nine of which are unique between the wheat subgenomes. One receptor TaPYL5.1 was recombinantly expressed, purified, and confirmed as an ABA receptor through a phosphatase based enzyme activity assay. A receptor with high sequence identity to TaPYL5.1, TaPYL5.2A, was targeted for plant trials because the TaPYL5.1 plasmid sequence was codon optimized. A VIGS approach was used to knock down TaPYL5.2A in planta. The TaPYL5.2A knockdown plants were found to have an increased resistance to Fusarium Head Blight progression in the early stages of the disease. In conclusion, wheat ABA receptors were successfully identified and an important correlation between decreased receptor levels and increased early Fusarium Head Blight resistance was found. This correlation however was not easily reproducible due to the severity of coupling VIGS with Fusarium Head Blight, and should be followed up with additional studies looking at the broader family of wheat ABA receptors.
DegreeMaster of Science (M.Sc.)
CommitteeMoore, Stan; Todd, Chris; Wang, Hong
Copyright DateJanuary 2016
Fusarium Head Blight