Résumé:
We exposed three species different of plants (basil, thyme, and the parsley) to four kinds of stress (the cold, darkness, water salt works, polluted water), and we left plants of each species like witnesses. This will cause a secretion of tannins. We studied the genetic and biochemical answer of these plants. We made a bioinformatic study in order to identify the sequence (AAA (C) Xn (A/C/G) CGCG (C/G/T) n≤ 18) (Taleb-Fromm consensus) in the promoter area of genes responsible of tannins biosynthesis, then we made a microbiological study to confirm what we found theoretically. In the bioinformatic study we located the sequence sought in the promoter area of genes coding for the enzyme of the anthocyanidine synthase, as well as the anthocyanidine réductase. These enzymes play a major part in the biosynthesis of tannins. The microbiological test showed that the extracts of the stressed plants have an important bactericidal effect compared to those that are in a normal state (not stressed). The stressed basil extracts showed an important inhibition zone with S.aureus compared to E.coli. For parsley and thyme we noticed the opposite i.e. the zone of inhibition were much more important with E.coli than with S.aureus. It means that as predicted from the bioinformatic study, the antibacterial power increases when the plants undergo stimuli. It was concluded that at the time of a stress, there will be a genetic answer by enzymatic reactions which results in the biosynthesis of tannins and other elements known by their therapeutic properties.
