The promoter of a gene encoding an isoflavone reductase-like protein in coffee (Coffea arabica) drives a stress-responsive expression in leaves

A cDNA clone (designated CaIRL) encoding an isoflavone reductase-like protein from coffee (Coffea arabica) was retrieved during a search for genes showing organ/tissue-specific expression among the expressed sequence tags (EST) of the Brazilian coffee EST database. The CaIRL cDNA contains a single open reading frame of 946 nucleotides (nt) encoding 314 amino acids (predicted molecular weight of 34 kDa). Several features identified the predicted CaIRL protein as a new member of the PIP family of NADPH-dependent reductases. Expression studies demonstrated that CaIRL is expressed exclusively in coffee leaves and its transcript level is markedly increased in response to fungal infection and mechanical injury. Analysis of transgenic tobacco plants harboring a CaIRL 5'-flanking region (862 nt) fused to uidA reporter gene (GUS) confirmed the responsiveness of the putative promoter to abiotic stress in wounded leaves. In turn, a 5' deletion to -404 completely abolished promoter activation by abiotic stimulus in transgenic plants. The lack of GUS expression in non-wounded leaf tissues in transgenic tobacco was in contrast to the basal level of CaIRL expression observed in non-stressed healthy coffee leaves.