p38 MAPK determines the sensitivity of the aquatic keystone species Moina macrocopa to toxic Microcystis: Insights into potential biomarker applications

Abstract

Harmful cyanobacterial blooms, particularly those caused by Microcystis species, pose significant ecological threats to freshwater environments by negatively impacting zooplankton populations, essential components of aquatic food webs. Understanding the molecular mechanisms underlying zooplankton responses to these toxic blooms is crucial for assessing and mitigating these impacts. The mitogen-activated protein kinase (MAPK) pathway, known for its critical role in stress response signaling, offers a promising area of study to elucidate these mechanisms. However, the specific involvement of MAPK in zooplankton responses to cyanobacterial stress remains unclear. In this study, we identify and characterize the p38 MAPK gene (MmMAPK) from the zooplankton Moina macrocopa. The gene contains conserved structural elements typical of MAPKs, including a Thr-Gly-Tyr (TGY) motif and a substrate-binding site, Ala-Thr-Arg-Trp (ATRW), indicating its potential functional relevance in stress signaling pathways. Expression analysis reveals a significant upregulation of MmMAPK in M. macrocopa upon exposure to toxic Microcystis, suggesting its role in mediating the organism's stress response. Furthermore, RNA interference (RNAi) experiments demonstrate that knockdown of MmMAPK results in reduced survival and decreased body size, particularly under cyanobacterial stress, underscoring its importance in maintaining stress sensitivity. These findings provide new insights into the molecular mechanisms by which M. macrocopa responds to harmful algal blooms and highlight the potential of MmMAPK as a biomarker for ecological risk assessment and management of cyanobacterial pollution in freshwater ecosystems.