Molecular cloning and nucleotide sequence of a gene encoding a cotton palmitoyl-acyl carrier protein thioesterase

A cotton genomic clone containing a 17.4-kb DNA segment was found to encompass a palmitoyl-acyl carrier protein (ACP) thioesterase (Fat B1) gene. The gene spans 3.6 kb with six exons and five introns, and is apparently the first plant FatB acyl-ACP thioesterase gene to be completely sequenced. The six exons are identical in nucleotide sequence to the open reading frame of the corresponding cDNA, and would encode a preprotein of 413 amino acids. The preprotein can clearly be identified as a FatB acyl-ACP thioesterase from its similarity to the deduced amino acid sequences of other FatB thioesterase preproteins. A 5'-flanking region of 914 bp was sequenced, with the potential TATA basal promoter 324 bp upstream from the ATG initiation codon. The 5'-flanking sequence also has a putative CAAT box and two presumptive basic region helixloop-helix (bHLH) elements with the consensus motif CANNTG (termed an E box), implicated as being a positive regulatory element in seed-specific gene expression.