Cloning And Sequence Analysis Of The Safflower Betaine Aldehyde Dehydrogenase (BADH) Gene

In response to salinity or drought stress, many plants accumulate glycine betaine, which is deemed a regulator of osmosis. In plants, the last step in betaine synthesis is catalyzed by betainealdehyde dehydrogenase (BADH), a nuclear encoded chloroplastic enzyme. Based on the conserved oligo amino acid residues of the published BADH genes from other higher plant species, a cDNA sequence, designated CtBADH, has been isolated from safflower (Carthamus tinctorius L.) using RACE and RT-PCR approach. The following results were obtained.1. Our sequence analysis indicated that the cloned full-length cDNA (1746bp) contains a1509bp ORF. The1509bp open reading frame encodes a503aa sequence. The deduced amino acid sequence showed a decapeptide Val-Thr-Leu-Geu-Leu-Gly-Gly-Lys-Ser-Pro and Cys,which are essential for the function of BADH. Alignment of the deduced CtBADH aa sequence and other plant BADH polypeptides shows an identity of about80%between the predicted amino acid sequences derived from safflower BADH gene and other plants (Glycine max, Gossypium hirsutum, Helianthus annum, Leymus chinensis, Oryza sativa, Populus trichocarpa, Zea mays,). The coding region was flanked by a144bp5’-untranslated region of the mRNA along with a full93bp3’-untranslate region.2. Phylogenetic analysis indicated safflower BADH was located in the branch of dicotyledonous plants, and subgrouped in the composites family (chrysanthemum lavandulifolium and helianthus annuus).3. Safflower BADH protein mainly contains alpha helixes and beta strands, which made up80%amino acids of the sequence. Analysis of the hydrophilic plot of our aa sequence showed that the hydrophobic areas were mainly in the two ends (N-terminal and C-terminal) of the aa sequence, and hydrophilic regions were mainly in the middle of safflower BADH.The consequence suggested that the senior structure composed of coils, alpha helixes and beta strands. This protein has33coils,15alpha helixes and21beta strands. Alpha helixes and beta strands appeared alternately. Beta strands were concentrated in the central, and surrounded by the external alpha helixes, and probably target to chloroplast or mitochondirion.