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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 AlCl 3 . The four CaPLC1-4 members showed changes in their transcript abundance upon AlCl 3 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 AlCl 3 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 AlCl 3 . 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 AlCl 3 . In non-treated cells, we observed a polar fluorescence signal towards the fused membrane. However, when cells were treated with AlCl 3 , these signals were disrupted. Finally, this is the first time that PLC activity has been shown to be stimulated in vitro by AlCl 3 ., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest., (Copyright © 2019. Published by Elsevier Inc.)

Toxicity by aluminum is a growth-limiting factor in plants cultivated in acidic soils. This metal also promotes signal transduction pathways leading to the biosynthesis of defense compounds, including secondary metabolites. In this study, we observed that Coffea arabica L. cells that were kept in the dark did not produce detectable levels of caffeine. However, irradiation with light and supplementation of the culture medium with theobromine were the best conditions for cell maintenance to investigate the role of aluminum in caffeine biosynthesis. The addition of theobromine to the cells did not cause any changes to cell growth and was useful for the bioconversion of theobromine to caffeine. During a short-term AlCl 3 -treatment (500μM) of C. arabica cells kept under light irradiation, increases in the caffeine levels in samples that were recovered from both the cells and culture media were evident. This augmentation coincided with increases in the enzyme activity of caffeine synthase (CS) and the transcript level of the gene encoding this enzyme (CS). Together, these results suggest that actions by Al and theobromine on the same pathway lead to the induction of caffeine biosynthesis., (Copyright © 2017 Elsevier Inc. All rights reserved.)