| Dof(DNA binding with one zinc finger)superfamily proteins are plant-specific transcription factors,playing important roles in the transcriptional level of diverse biological processes,including seed germination,plant growth and development,metabolic regulation and response to environmental cues.It has been demonstrated that Dof superfamily proteins mainly act through plant hormones in the regulation of plant development.Ethylene also plays roles in plant growth and development,however,whether and how Dof proteins function with ethylene in these processes has not been reported.To identify the factors involved in this crosstalk,we found that a Dof protein in rice,OsDof15,participates in ethylene biosynthesis.OsDof15(LOC_Os03g55610)encodes a typical C2H2 type Dof transcription family protein in rice.Sequence alignment and phylogenetic analysis showed that there are homologous proteins of Os Dof15 in a variety of plants.It could functions as a transactivator.The expression of OsDof15 was detected in root,stem,leaf,sheaths and spikelet,with the highest level in root.In addition,the gene expression of OsDof15 was induced by NaCl,drought,ABA,and ethylene treatment.These results reveal that OsDof15 functions in roots growth and in the response to osmotic stress.The phenotype observeation shows that OsDof15 can positively regulate roots development in rice seedling stage.OsDof15 can control the cell length of roots department in the maturation zone,the elongation zone,the meristematic zone and quiescent center(QC).And OsDof15 can regulate roots development through ethylene biosynthesis pathway.In addition,the gene expression and chromatin immunoprecipitation(ChIP)experiment show that OsDof15 can bind to the promoter of OsACS1 to regulate its expression,revealing that OsDof15 is involved in rice seedling development by transcriptionally regulating OsACS1 expression and ethylene biosynthesis.The function of ethylene in plants depends on ethylene signal pathway.To find out more ethylene signaling proteins,we obtained three ethylene root insensitive mutants by ethylene treatment from the mutant library.We selected one of the mutants,D814,for further research,showing the dwarf phenotype,less effective tilling numbers and 1000-grain weight.The mutation of D814 was mapped to 1 cM range at chromosome 1 through map-based cloning,containing six genes that have evidenced to contribute to dwarf phenotype in the previous researches.Sequencing analyses demonstrated that there were no any mutations in the above mentioned 5 genes,except in OsBRI1(LOC_Os01g52050),with C changed to A at 1837 point in CDS.Moreover,the result showed that D814 displayed salt response and might be involved in ethylene signaling pathway.Thus,our results show that OsDof15 possitively regulates root development by inhibiting ethylene biosynthesis.This research is signifcal important for exploring ethylene signal pathway. |
