Identification And Expression Analysis Of Sulfate Transporter Gene Family From Maize

Sulfate transporters,which are responsible for transporting and absorbing sulfates,are important transporters in the sulfur metabolism pathway in plants.In this paper,preliminary molecular analyses on sulfate transporters in maize were conducted.The main results are as follows:1.Twelve Arabidopsis and eleven rice SULTR protein sequences were used as query sequences for BLASTN searches in the maize database with default parameters.Eight putative SULTR genes were identified in the maize genome.The sequence alignment and phylogenetic tree analysis of SULTRs between maize were performed by DNAstar and MEGA 6,respectively.Our phylogenetic analyses of the SULTR proteins in maize were found to be homologous to their corresponding members of the SULTR family in rice(60–86% similarities)and Arabidopsis(55–67% similarities).2.Transcriptional expression of ZmSULTR genes in response to sulfate deprivation.The real-time quantitative PCR technique was used to analyze transcriptional patterns of ZmSULTR genes in various organs of maize and the transcriptional levels of ZmSULTR genes in response to sulfate deprivation.Higher root expression was found for ZmSULTR1;1 and ZmSULTR4;1,while higher shoot transcript levels were observed for ZmSULTR3;1 and ZmSULTR3;3.Expression of the eight ZmSULTR genes was examined at the reproductive growth stage.In tassels,the four ZmSULTR genes,ZmSULTR1;2,ZmSULTR2;1,ZmSULTR3;3,and ZmSULTR4;1,showed highest transcript levels.In contrast,all the eight ZmSULTR genes exhibited low transcript levels in the immature ears.3.Expression analysis of ZmSULTR genes in response to abiotic stress.Under salt stress,expression of ZmSULTR1;2 was increased gradually and reached its peak at 24 h of the treatment period.Expression of ZmSULTR1;1,ZmSULTR3;1,ZmSULTR3;3,ZmSULTR3;5,and ZmSULTR4;1 showed significant increases at 6 or 12 h of the stress,and then decreased to stable level.Under dehydration stress,all the ZmSULTR genes,except for ZmSULTR3;3 and ZmSULTR4;1,were significantly activated by dehydration.This trend was clearly seen at 6 and 12 h of the stress period.Under heat stress,expression of ZmSULTR1;1,ZmSULTR1;2,ZmSULTR3;1,ZmSULTR3;5,and ZmSULTR4;1 showed significant increases at 3 or 6 h of the stress with a peak at 6 h,and then decreased to stable levels during the whole period(24 h)of treatments.These results indicate that most ZmSULTR genes are induced by salt,dehydration,and heat stress.4.The promoter sequences from ZmSULTR1;1(ZmSULTR1;1-P),ZmSULTR1;2(ZmSULTR1;2-P)and ZmSULTR3;3(ZmSULTR3;3-P)were cloned in maize inbred line B73.The plant expression vectors harboring the promoter sequences fused to the GUS coding sequences were constructed and expressed in the tobacco seedlings via the agrobacterium-mediated transformation.GUS staining has shown that ZmSULTR1;1-P and ZmSULTR3;3-P are expressed at the leaf or petiole of tobacco,while the ZmSULTR1;2-P is very weak.5.ZmSULTR1;2-P sequences were cloned from the maize inbred lines B73 and Cml115,respectively,and sequence alignment showed that there exist several fragment In Dels between these two sequences.GUS staining revealed that the ZmSULTR1;2-P derived from Cml115 showed much higher activity than that from the B73.6.Subcellular localization in tobacco showed that ZmSULTR1;2 was localized on the plasma membrane.