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 a...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.展开更多
Strigolactones （SLs） are a class of plant hormones that control plant development in response to environmental conditions. In rice, mesocotyl elongation is regulated by SLs in the dark, while mesocotyls are longer i...Strigolactones （SLs） are a class of plant hormones that control plant development in response to environmental conditions. In rice, mesocotyl elongation is regulated by SLs in the dark, while mesocotyls are longer in SL deficient or insensitive mutants. SLs are perceived by DWARF14 （D14）, which is a member of a small gene family. In this study, we examined the function of another D14 family gene in rice, D14 LIKE （D14L）, focusing on mesocotyl growth. The mesocotyls of D14L RNAi lines are longer than those of WT in the dark. This phenotype is enhanced when the D14L RNAi lines are combined with the d14 mutation, suggesting that D14 and D14L work independently to inhibit mesocotyl elongation. This phenotype is alleviated by the exogenous supply of GR24, a synthetic SL, suggesting that D14L is not necessary for SL signaling. D14L mRNA is predominantly expressed in vascular bundles and crown root primordia. Our results suggest that D14L and D14 confer their effects via an SL independent pathway and an SL signaling pathway respectively.展开更多
文摘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.
基金supported by a grant from the Promotion of Basic Research Activities for Innovative Biosciences (PROBRAIN) of Japan to J.K
文摘Strigolactones （SLs） are a class of plant hormones that control plant development in response to environmental conditions. In rice, mesocotyl elongation is regulated by SLs in the dark, while mesocotyls are longer in SL deficient or insensitive mutants. SLs are perceived by DWARF14 （D14）, which is a member of a small gene family. In this study, we examined the function of another D14 family gene in rice, D14 LIKE （D14L）, focusing on mesocotyl growth. The mesocotyls of D14L RNAi lines are longer than those of WT in the dark. This phenotype is enhanced when the D14L RNAi lines are combined with the d14 mutation, suggesting that D14 and D14L work independently to inhibit mesocotyl elongation. This phenotype is alleviated by the exogenous supply of GR24, a synthetic SL, suggesting that D14L is not necessary for SL signaling. D14L mRNA is predominantly expressed in vascular bundles and crown root primordia. Our results suggest that D14L and D14 confer their effects via an SL independent pathway and an SL signaling pathway respectively.
