Cloning and Activity of DlAGO4 and DlAGO6 Promoters from Dimocarpus longan

  Objective   Argonaute (AGO) proteins play the important roles in a wide varieties of plant biological processes. To explore the cis --acting elements of DlAGO4 and DlAGO6 promoters, the expression patterns of recombinant vector of DlAGO4 and DlAGO6 promoters under different hormones treatments in longan, DlAGO4 and DlAGO6 promoters in longan were cloned and analyzed.

  Method  Promoters of DlAGO4 and DlAGO6 from Dimocarpus longan were cloned by PCR for a bioinformatic analysis. Fusion expression vectors of the full-length promoters and GUS gene were constructed. The Agrobacterium tumefaciens-mediated transformation was performed on protocorm of tobacco leaves to observe the transient expression of the genes, while promoter activity examined by GUS histochemical staining.

  Result   The sequence of DlAGO4 promoter was 1 514 bp and the sequence of DlAGO6 promoter was 1 784 bp. Both had the core elements of TATA- and CAAT-box as well as ababolic acid (ABA), methyl jasmonate (MeJA), and photoresponsive elements. The DlAGO4 promoter also contained salicylic acid (SA), gibberellin response, and anaerobic response regulatory elements, while the DlAGO6 promoter had auxin and circadian rhythm regulatory elements. The promoters exhibited a GUS-driving activity that was weaker than CaMV35S. The relative expression of GUS of P_DlAGO6::GUS recombinant tobacco leaf was significantly elevated by the treatment of MeJA and ABA, whereas that of P_DlAGO4::GUS recombinant tobacco leaf by SA and MeJA.

  Conclusion   The promoters of DlAGO4 and DlAGO6 from longan were successfully cloned. As hormone-induced promoters, they could activate the GUS expression and be involved in the somatic embryo development and hormone response of plants.