Karrikins are a class of seed germination stimulants identified in smoke from wildfires. Microarray analysis of imbibed Arabidopsis thaliana seeds was performed to identify transcriptional responses to KAR₁ before germination. A small set of genes that are regulated by KAR₁, even when germination is prevented by the absence of gibberellin biosynthesis or light, were identified. Light-induced genes, putative HY5-binding targets, and ABRE-like promoter motifs were overrepresented among KAR₁-up-regulated genes. KAR₁ transiently induced the light signal transduction transcription factor genes HY5 and HYH. Germination of afterripened Arabidopsis seed was triggered at lower fluences of red light when treated with KAR₁. Light-dependent cotyledon expansion and inhibition of hypocotyl elongation were enhanced in the presence of germination-active karrikins. HY5 is important for the Arabidopsis hypocotyl elongation, but not seed germination, response to karrikins. These results reveal a role for karrikins in priming light responses in the emerging seedling, and suggest that the influence of karrikins on postfire ecology may not be limited to germination recruitment.

Item Type:	Refereed Article
Keywords:	smoke, photomorphogenesis, karrikins, arabidopsis thaliana, smoke
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:	101472
Year Published:	2010
Web of Science® Times Cited:	95
Deposited By:	Plant Science
Deposited On:	2015-06-24
Last Modified:	2015-09-22
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