The signaling role of extracellular ATP in co-culture of Shiraia sp. S9 and Pseudomonas fulva SB1 for enhancing hypocrellin A production

Xin Ping Li,Jian Wen Wang,Yan Hua Guo,Lu Lu Zhou

doi:10.1186/s12934-021-01637-9

Abstract

BackgroundAdenosine 5′-triphosphate (ATP) plays both a central role as an intracellular energy source, and a crucial extracellular signaling role in diverse physiological processes of animals and plants. However, there are less reports concerning the signaling role of microbial extracellular ATP (eATP). Hypocrellins are effective anticancer photodynamic therapy (PDT) agents from bambusicolous Shiraia fungi. The co-culture of Shiraia sp. S9 and a bacterium Pseudomonas fulva SB1 isolated from Shiraia fruiting bodies was established for enhanced hypocrellin A (HA) production. The signaling roles of eATP to mediate hypocrellin biosynthesis were investigated in the co-culture.ResultsThe co-culture induced release of eATP at 378 nM to the medium around 4 h. The eATP release was interdependent on cytosolic Ca2+ concentration and reactive oxygen species (ROS) production, respectively. The eATP production could be suppressed by the Ca2+ chelator EGTA or abolished by the channel blocker La3+, ROS scavenger vitamin C and NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI). The bacterium-induced H2O2 production was strongly inhibited by reactive blue (RB), a specific inhibitor of membrane purinoceptors, but dependent on the induced Ca2+ influx in the co-culture. On the other hand, the application of exogenous ATP (exATP) at 10–300 µM to Shiraia cultures also promoted fungal conidiation and HA production, both of which were blocked effectively by the purinoceptor inhibitors pyridoxalphosphate-6-azophenyl-2′, 4′-disulfonic acid (PPADS) and RB, and ATP hydrolase apyrase. Both the induced expression of HA biosynthetic genes and HA accumulation were inhibited significantly under the blocking of the eATP or Ca2+ signaling, and the scavenge of ROS in the co-culture.ConclusionsOur results indicate that eATP release is an early event during the intimate bacterial–fungal interaction and eATP plays a signaling role in the bacterial elicitation on fungal metabolites. Ca2+ and ROS are closely linked for activation of the induced ATP release and its signal transduction. This is the first report on eATP production in the fungal–bacterial co-culture and its involvement in the induced biosynthesis of fungal metabolites.Graphic abstract

Highlights

Adenosine 5′-triphosphate (ATP) plays both a central role as an intracellular energy source, and a crucial extracellular signaling role in diverse physiological processes of animals and plants
Ding and Tan found that extracellular ATP (eATP) induced dispersal of a periodontal associated bacterium Fusobacterium nucleatum with enhanced virulence to elicit inflammation in periodontal disease [11]. eATP was reported as a damage-associated molecular pattern (DAMP) to induce the influx of cytosolic free calcium ([Ca2+]cyt) and activate the mitogen activated protein kinase (MAPK) Tmk1 for hyphal regeneration of a filamentous fungus Trichoderma atroviride under mechanical damage [12, 13]
A significant increase of the eATP was observed after 15 min and its concentration peaked at 378 nM around 4 h (Fig. 1d)

Summary

Introduction

Adenosine 5′-triphosphate (ATP) plays both a central role as an intracellular energy source, and a crucial extracellular signaling role in diverse physiological processes of animals and plants. There are less reports concerning the signaling role of microbial extracellular ATP (eATP). The signaling roles of eATP to mediate hypocrellin biosynthesis were investigated in the co-culture. EATP initiates the early physiological responses, such as triggering C a2+ influx, stimulating generation of reactive oxygen species (ROS), and up-regulating expression of mitogen activated protein kinase (MAPK) gene, and later responses such as induced defense gene expression and disease resistance [7]. There was a report of exogenous ATP (exATP) to enhance tautomycetin in Streptomyces griseochromogenes [14], less reports have been found concerning the signaling role of eATP on the biosynthesis of microbial secondary metabolites

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