Wildfires can encourage the establishment of invasive plants by releasing potent germination stimulants, such as karrikins. Seed germination of Brassica tournefortii, a noxious weed of Mediterranean climates, is strongly stimulated by KAR1, the archetypal karrikin produced from burning vegetation. In contrast, the closely-related yet non-fire-associated ephemeral Arabidopsis thaliana is unusual because it responds preferentially to KAR2. The α/β-hydrolase KARRIKIN INSENSITIVE 2 (KAI2) is the putative karrikin receptor identified in Arabidopsis. Here we show that B. tournefortii expresses three KAI2 homologues, and the most highly-expressed homologue is sufficient to confer enhanced responses to KAR1 relative to KAR2 when expressed in Arabidopsis. We identify two amino acid residues near the KAI2 active site that explain the ligand selectivity, and show that this combination has arisen independently multiple times within dicots. Our results suggest that duplication and diversification of KAI2 proteins could confer differential responses to chemical cues produced by environmental disturbance, including fire.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Plant biology
Research Field:	Plant physiology
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the biological sciences
UTAS Author:	Smith, SM (Professor Steven Smith)
ID Code:	151163
Year Published:	2020
Funding Support:	Australian Research Council (DP140104567)
Web of Science® Times Cited:	18
Deposited By:	Plant Science
Deposited On:	2022-07-23
Last Modified:	2022-07-23
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