The Expression Regulation Of Alkaline Ceramidase TOD1 And Phytoceramidase Screening In Arabidopsis

Arabidopsis TOD1(TurgOr regulation Defect 1)encodes an alkaline ceramidase that is involved in turgor regulation during pollen tube growth and silique stomatal movement.TOD1 is preferentially expressed in pollen and silique guard cells.Loss-of-function mutants showed reduced fertility due to defects in pollen transmission,while the aborted fertilization phenotype recovered in the todl ?4-desaturase double mutant.Sphingolipids are the most important lipids as eukaryotic membrane components.They also play essential roles in plant development and abiotic or biotic stresses responses.Ceramides are a kind of key intermediate metabolites of plant sphingolipids and are critical for plant growth and development.The aims of this study is to test whether transcription factors,ABI3 and ABI5,regulate the expression of TOD1 by binding to its promoter region,which may help us gain a better understanding of the molecular regulation of sphingolipids metabolism,and to screen candidate genes encoding phytoceramidase from TOD1 family members.Electrophoretic mobility shift assays(EMSA)and chromatin immunoprecipitation(ChIP)results indicated that ABI5 is able to bind to the promoter region of TOD1;Real-time PCR results showed that the expression level of At1G28240 was increased in tod1 ?4desaturase double mutant,which suggests that it may encodes a candidate phytoceramidase;Enzyme activity experiments revealed that At2G02910,At5G42660,At1G28240 and At4G09630 did not show phytoceramidase activity at pH 9.4.