Objective  A functional analysis was conducted on the cloned bZIP transcription factor in cassava.

  Method   The coding sequence (CDS) of ZIP2 in Cassava SC205 was amplified to perform a bioinformatic analysis in determining the subcellular localization and expression of MebZIP2. A pNC-green-subN fusion expression vector was constructed and transferred into tobacco epidermal cells using the Agrobacterium-mediated method. Fluorescence signals were observed for subcellular localization of the protein. Expressions of MebZIP2 in tissues at different stages of storage root development of the plant were determined. Interactions between MebZIP2 and the promoters of starch synthesis genes were analyzed by the yeast one-hybrid assay.

  Result   The CDS of MebZIP2 was 465 bp long encoded 154 amino acids with a molecular weight of 17 891.35 Da and an isoelectric point of 5.23. The unstable hydrophilic protein contained a bZIP-conserved domain with the highest sequence similarity to that of one of Hevea brasiliensis at 74.22%. The promoter region of MebZIP2 included responsive elements to light, hormones (such as gibberellin, salicylic acid, and jasmonic acid), endosperm expression, and stresses. The protein localized in the cell membrane as well as the nucleus. The gene expressed highly in the root apical meristems, fibrous roots, stems, and at early development stages of storage roots and co-expressed with those involved starch synthesis, such as MeAPL5a, MeGBSS1, and MeISA1, whose promoters could interact with the protein.

  Conclusion  Belonging to the bZIP family associated with plant growth, development, starch synthesis, and resistance to abiotic stress, MebZIP2 exhibited a tissue- and root development stage-specific expression. The protein interacted with the promoters of MeAPL5a, MeGBSS1, and MeISA1 related to starch synthesis in the plant. It might also be involved in cassava storage root development.