The grey mould fungus Botrytis cinerea is capable of developing on a wide variety of host plants and different organs that differ greatly in their pH values. The strategy developed by this necrotrophic fungus is partly based on the acidification of the plant tissues via the secretion of several organic acids including oxalic acid. That’s why B.cinerea is considered as an “acidic” fungus. However, we have previously shown that it is also capable of alkalinizing its ambient environment during sunflower cotyledons or bean leaves infection and that the alkalinization is achieved by amino acids catabolism and ammonia secretion ( Billon-grand et al, 2012). This capacity to modulate the surrounding pH reveals also an ability to regulate the expression and the secretion of an arsenal of enzymes in order to produce virulence factors in accordance with the ambient pH and enzymes requirement for optimal activity. Expression of pH-regulated genes is controlled by the highly conserved signaling pathway Pal/Pac that leads to activation of the zinc finger transcription factor PACC under neutral or alkaline conditions. Investigations of the role of this pH regulator in the infectious process of B.cinerea are presented.