Functional Analysis Of 5’ Regulatory Region Of ZmAGA1 Gene

As a major crop, the corn production is restricted by various abiotic stresses, such as drought, high tempreture, low tempreture and high salinity. Raffinose plays important roles in abiotic stress tolerance in plants. ALKALINE ALPHA GALACTOSIDASE(AGA) is responsible for raffinose hydrolysis. Previous work has demonstrated that ZmAGA1 gene is induced by heat stress in germinating seeds. To investigate the expression regulation of ZmAGA1 under abiotic stress, the expression profile of ZmAGA1 in maize seedlings treated by draught, heat shock and salt stress were determined by real time RT-PCR. The cis-elements in the promoter of ZmAGA1 were also indentified by transient expression of a reporter gene controlled by ZmAGA1 promoter fragments in maize protoplasts. ZmAGA1 was upregulated by dyhydration, heat shock and salt stress in maize developing leaves. The 1622 bp of 5’ flanking sequence(relative to the start codon ATG) was cloned and tested for promoter activity. The 5’ deletion assay of ZmAGA1 promoter indicated that the fragment of-421 to-1 had the greatest promoter activity. An ABRE(ABA responsive element) in the ZmAGA1 promoter was identified to be functional. A 6 nt RNA motif in the 5’UTR of ZmAGA1 mRNA was identified to regulate the downstream ORF translation. Some cytosolic proteins were confirmed to bind to the 6 nt RNA motif by RNA-EMSA.