Biochemical characterization of phospholipases C from Coffea arabica in response to aluminium stress

Signal transduction in plants determines their successful adaptation to diverse stress factors. Our group employed suspension cells to study the phosphoinositide pathway, which is triggered by aluminium stress. We investigated about members of the PI-specific phospholipase C (PLC) family and evaluated their transcription profiles in Coffea arabica (Ca) suspension cells after 14days of culture when treated or not with 100μM AlCl₃. The four CaPLC1-4 members showed changes in their transcript abundance upon AlCl₃ treatment. The expression profiles of CaPLC1/2 exhibited a rapid and transitory increase in abundance. In contrast, CaPLC3 and CaPLC4 showed that transcript levels were up-regulated in short times (at 30s), while only CaPLC4 kept high levels and CaPLC3 was reduced to basal after 3h of treatment. CaPLC proteins were heterologously expressed, and CaPLC2 and CaPLC4 were tested for in vitro activity in the presence or absence of AlCl₃ and compared to Arabidopsis PLC2 (AtPLC2). A crude extract was isolated from coffee cells. CaPLC2 showed a similar inhibition (30%) as in AtPLC2 and in the crude extract, while in CaPLC4, the activity was enhanced by AlCl₃. Additionally, we visualized the yellow fluorescent protein PH domain of human PLCδ1 (YFP-PH_PLCδ1) subcellular localization in cells that were treated or not with AlCl₃. In non-treated cells, we observed a polar fluorescence signal towards the fused membrane. However, when cells were treated with AlCl₃, these signals were disrupted. Finally, this is the first time that PLC activity has been shown to be stimulated in vitro by AlCl₃.