KAI2-and MAX2-Mediated Responses to Karrikins and Strigolactones Are Largely Independent of HY5 in Arabidopsis Seedlings

• Published in: Molecular plant Vol. 6; no. 1; pp. 63 - 75
• Main Authors: Waters, Mark T., Smith, Steven M.
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 2013
• Subjects: Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis - radiation effects; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Basic-Leucine Zipper Transcription Factors - metabolism; Carrier Proteins - genetics; Carrier Proteins - metabolism; Furans - pharmacology; Gene Expression Regulation, Plant - drug effects; Gene Expression Regulation, Plant - radiation effects; Genetic Complementation Test; HY5; Hydrolases - genetics; Hydrolases - metabolism; Hypocotyl - drug effects; Hypocotyl - growth & development; Hypocotyl - radiation effects; KAI2; karrikin; Lactones - pharmacology; Light; MAX2; Models, Biological; Nuclear Proteins - metabolism; Phenotype; photomorphogenesis; Pyrans - pharmacology; RNA, Messenger - genetics; RNA, Messenger - metabolism; Seedlings - drug effects; Seedlings - genetics; Seedlings - metabolism; Seedlings - radiation effects; smoke; strigolactone; 介导; 光形态建成; 内酯化合物; 幼苗生长发育; 拟南芥; 种子萌发; 金; smoke; photomorphogenesis; KAI2; HY5; strigolactone; karrikin
• ISSN: 1674-2052; 1752-9867
• DOI: 10.1093/mp/sss127

Karrikins are butenolide compounds released from burning vegetation that stimulate seed germination and enhance seedling photomorphogenesis. Strigolactones are structurally similar plant hormones that regulate shoot and root development, and promote the germination of parasitic weed seeds. In Arabidopsis, the F-box protein MAX2 is required for responses to karrikins and strigolactones, and the a/~ hydrolase KAI2 is necessary for responses to karrikins. Both MAX2 and KAI2 are essential for normal light-dependent seedling development. The bZIP transcription factor HY5 acts downstream of multiple photoreceptors and promotes photomorphogenesis, but its relationship with MAX2 and KAI2 in terms of seedling development and responses to karrikins and strigolactones is poorly defined. Here, we dem- onstrate that HY5 action is genetically separable from that of MAX2 and KAI2. While by5 mutants have weak hypoco- tyl elongation responses to karrikins and the artificial strigolactone GR24, they have normal transcriptional responses, suggesting that HY5 is not involved in perception or action of karrikins or strigolactones. Furthermore, we show that overexpression of KAI2 is sufficient to enhance responses to both karrikins and GR24 in wild-type seedlings, and that KAI2 overexpression partially suppresses the hy5 long hypocotyl phenotype. These results suggest that KAI2 and MAX2 define a regulatory pathway that largely operates independently of HY5 to mediate seedling responses to abiotic signals such as smoke and light.