Gene MebZIP de mandioca: caracterização da proteína deduzida e avaliação do padrão de expressão gênica em condições de luminosidade

Abstract

Proteins of bZIP family (from Basic Leucine Zipper Domain, bZIP domain) are regulatory proteins that occur in eukaryotes and exhibit a basic DNA-binding domain, and a dimerization domain containing conserved leucine residues, known as leucine zipper. In plants, bZIPs act on the transcriptional regulation of genes involved in various biological processes, including responses to biotic and abiotic factors. Previous studies have identified a partial cDNA sequence encoding a bZIP protein, named MebZIP, containing 334 amino acid residues (aa) with expression in the root and leaf cassava (Manihot esculenta Crantz). Here, with the objective of complementing the identification and characterization of MebZIP, RACE (Rapid Amplification of cDNA Ends) assays were performed in order to isolate the 3' end of this cDNA. Bioinformatics analyzes showed that the MebZIP full-length cDNA has a 1320 bp Open Reading Frame (ORE) coding for a deduced protein with 439 aa with predicted molecular weight and isoelectric point of 47 kDa and 5.85, respectively. Comparativo analyzes with GenBank sequences showed high identity of MebZIP with the M. esculenta CPRF-2 (XP_021620722) and Hevea brasiliensis CPRF-2 (XP_021650934) proteins, including the presence of conserved domains. Literatura data show that CPRF-2 proteins may participate in the regulation of the chalcone synthase gene (CHS), whose expression may be influenced by exposure to light. Thus, semiquantitative RT-PCR assays were performed to evaluate the expression of the MebZIP and MeCHS genes in cassava leaves submitted to different periods of exposure to white light (Oh, 3h, 6h, 9h, 12h and 15h). Results showed an increased MebZIP expression levei in the 6h sample, however, no relationship was detected with the expression leveis of the potential target gene for the MebZIP, the MeCHS, which remained constant under the conditions used here. Based on our results, we can conclude that the MebZIP identified here contains conserved domains (bZIP, D1-D4) indicating its functionality as a member of bZIP CPRF family with potential role in the light response of cassava.