Cloning And Functional Analysis Of A Novel Sugar Transporter Gene ZmERD6 From Maize

The ERD6 gene family is a Sugar transporter family which sequences are specific. It is widely exists in plants. ERD6 genes play diverse roles in plant development. According to the phylogenetic analysis, the Sugar transporter genes in plants belong to Major Facilitator Super-family and are divided into three groups named SUT1,SUT2 and SUT4. And the members of Sugar transporter have a typical structure of MFS domain and Sugar transport proteins signature.Previously one EST with high similarity to ERD6 in Arabidopsis was found in maize. In the present study, cDNAs for the gene homologous to ERD6, designated ZmERD6, was obtained through in silico and homology-based cloning techniques. ZmERD6 had two transcripts, i.e. ZmERD6-L (the large one) and ZmERD6-S (the small one). ZmERD6-L had an ORF of 1515 bp and encoded 505 amino acids (AA), while ZmERD6-S had an ORF of 1386 bp and encoded 462AA. The deduced proteins of ZmERD6-L and ZmERD6-S were predicted to contain 12 and 11 membrane spanning helices, respectively. Both proteins had two MFS structural domains belonging to the sugar transporter sub-family of the MFS (major facilitator super-family). Reverse transcription-PCR analysis was performed to investigate the expression pattern of the ZmERD6 in maize under various abiotic stresses. ZmERD6 expressed at different stages through maize development and was also induced by different abiotic stresses.The promoter of ZmERD6 was cloned, which was about 2.5 kb upstream of ZmERD6. Important regulatory elements including core promoter elements, enhancer elements, repressor elements and low-temperature and MeJA-responsive elements were predicted. These results suggest that the gene is a novel sugar transporter gene in maize and has important and diverse roles in tolerance to abiotic stresses.Arabidopsis plants with double-stranded ZmERD6 RNA were generated through transformation via Agrobacterium. Transgenic plants showed a higher germination rate on mannitol or sodium chloride containing medium than wild type plants. The contents of proline and sugar of transgenic plants were higher than that of wild type under drought stress. All results indicate that ZmERD6 has an important role in response to abiotic stress.