What question did this study set out to answer?

This research aims to characterize the phytochelatin synthase gene in Scenedesmus acutus and understand its role under chromium stress and varying sulfur availability.

February 8, 2026Open Access

Adaptive Plasticity of Phytochelatin Synthase Under Chromium Stress and Sulfur Availability in Scenedesmus acutus

Key Points

This research aims to characterize the phytochelatin synthase gene in Scenedesmus acutus and understand its role under chromium stress and varying sulfur availability.
Characterization of the PCS gene in Scenedesmus acutus from wild-type and chromium-tolerant strains.
Utilization of RT-qPCR, immunoblotting, and mass spectrometry for analysis.
Investigation of protein isoforms and alternative splicing of the PCS gene.
SaPCS expression varies primarily with sulfur availability, not chromium stress.
Two protein isoforms of SaPCS were identified, more abundant in chromium-tolerant strains.
Phytochelatin production in response to chromium is negligible, indicating reliance on glutathione for detoxification.

Abstract

Phytochelatin synthases (PCSs) are pivotal enzymes in heavy metal detoxification, yet also implicated in sulfur homeostasis and redox regulation. In this study, we report the molecular and functional characterization of the PCS gene from the green alga Scenedesmus acutus (SaPCS), comparing wild-type and chromium-tolerant strains of this microalga. RT-qPCR, immunoblotting and mass spectrometry analyses revealed that SaPCS expression and protein abundance are primarily regulated by sulfur availability rather than by chromium stress. Two protein isoforms (~70 kDa full-length and ~34 kDa truncated) were detected, both more abundant in the chromium-tolerant strain than the wild-type and responsive to sulfur availability. Furthermore, three alternatively spliced transcript variants (SaPCSa, SaPCSb, SaPCSc) lacking the C-terminal domain coding region but retaining a functional or partially disrupted N-terminal catalytic domain were identified, contributing to the post-transcriptional diversification of PCSs. Mass spectrometry analyses showed negligible phytochelatin production in response to chromium treatment, indicating that detoxification of this metal in S. acutus relies mainly on glutathione (GSH) conjugation and the ascorbate–GSH antioxidant cycle. Overall, these results suggest that SaPCS may promote chromium tolerance by modulating sulfur and redox metabolism rather than by driving phytochelatin accumulation, highlighting the remarkable functional plasticity of PCSs in algal stress responses.

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