148 



SUMMARY 



In conclusion, with the cloning of the aroD^aroE cDNA 

 encoding the S-protein (the first to be cloned and sequenced 

 in higher plants) , other studies may now be undertaken. 

 First of all, a complete sequence is desirable, since it is 

 proposed that the 5' region has been truncated. This may be 

 accomplished by obtaining mRNA from Nicotiana tabacum plants 

 for primer extension. Other studies may include cloning of 

 the gene from a genomic library, determining the number of 

 gene copies in Silvestris or in other plant species by use 

 of Southern blots, performing site directed mutagenesis or 

 chemical treatment to study the active site residues, use of 

 the cloned cDNA coding for the S-protein as a probe to 

 obtain the cDNA from other plants and to determine what the 

 cytosolic pathway has with respect to dehydroquinase and 

 shikimate dehydrogenase. The probable location of the 

 bifunctional gene product in the chloroplast remains to be 

 proven. Clarification of the relationship of SP-I and SP-II 

 is needed. The possibilities are: (i) that one is an 

 artifact of limited proteolysis, (ii) that one is an 

 active, uncleaved preprotein in the cytosol, (iii) or that 

 they are separately subcompartmented in the chloroplast . 



