The pyridoxal kinase gene TaPdxK from wheat complements vitamin B6 synthesis-defective Escherichia coli

Pyridoxal kinase (EC 2.7.1.35) is a key enzyme in the conversion of vitamin B6 to pyridoxal 5′-phosphate (PLP). PLP is the crucial cofactor required by numerous enzymes involved in amino acids metabolism. Recently, studies with Arabidopsis salt overly sensitive 4 mutants demonstrated that pyridoxal kinase is a novel salt tolerance determinant important for the regulation of Na+ and K+ homeostasis in plants. We describe here the TaPdxK gene which encodes a pyridoxal kinase, cloned from Triticum aestivum by RACE PCR method. The putative amino acid sequence of TaPdxK is 78% identical to Arabidopsis AtSOS4. Southern analysis suggests that there are at least two copies of pyridoxal kinase genes in wheat genome. The expression of TaPdxK cDNAs complements an Escherichia coli mutant defective in pyridoxal kinase. TaPdxK transcripts were detected in roots, shoots, spikes and anthers by RT-PCR analysis. TaPdxK expression level was not regulated by salt, ABA, and osmotic stress.