DEVELOPMENTAL, CIRCADIAN AND LIGHT REGULATION OF WHEAT FERREDOXIN GENE-EXPRESSION

A genomic clone encoding the precursor of wheat leaf ferredoxin has be en isolated and characterised. The uninterrupted PetF gene encodes a p olypeptide of 143 amino acid residues, consisting of an N-terminal pre sequence of 46 amino acid residues and a mature polypeptide of 97 amin o acid residues. Southern blot analysis suggests that six copies of th e PetF gene are present in the wheat haploid genome. Northern blot ana lysis has shown that the genes are both developmentally and light regu lated in wheat seedlings and provides evidence that a circadian rhythm regulates the steady-state levels of ferredoxin transcripts. The inta ct wheat gene and several chimeric constructs, containing portions of the 5'-upstream region fused to the beta-glucuronidase reporter gene, have been introduced into tobacco plants, but levels of beta-glucuroni dase activity above background were not detected, suggesting that the 5'-upstream region is unable to function as a promoter in tobacco plan ts.