Cadmium induced mitochondrial redox changes in germinating pea seed

Area of Science:

• Plant Physiology
• Biochemistry
• Environmental Toxicology

Background:

• Mitochondria are crucial for energy production during seed germination.
• Heavy metals like cadmium disrupt mitochondrial function by altering redox regulation.
• Protein redox systems, including thioredoxin (Trx) and glutaredoxin (Grx), are key regulators of mitochondrial redox balance.

Purpose of the Study:

• To investigate the impact of cadmium (Cd) on mitochondrial thioredoxin and glutaredoxin systems in pea (Pisum sativum L.) seeds during germination.
• To analyze the differential redox responses in cotyledons and embryos of pea seeds exposed to toxic Cd concentrations.
• To understand how Cd toxicity affects key components of redox regulation in plant seeds.

Main Methods:

• Analysis of thioredoxin (Trx) and glutaredoxin (Grx) system activities in pea seed cotyledons and embryos.
• Quantification of glutathione (GSH) and total NAD(P) content under cadmium stress.
• Measurement of oxidative stress parameters, including coenzyme redox ratios and NAD(P)H oxidase activity.

Main Results:

• Cadmium exposure decreased total soluble protein but increased -SH content in pea seeds.
• Glutaredoxin (Grx) and glutathione reductase (GR) activities, along with glutathione (GSH) concentrations, were reduced in both cotyledons and embryos under Cd stress.
• While the Trx system was not stimulated in the embryo, Cd enhanced all Trx system components in the cotyledons, despite increased oxidative stress markers.

Conclusions:

• Cadmium induces differential redox responses in pea seed tissues, with distinct effects on cotyledons and embryos.
• The Grx system and Trx system in the embryo appear unable to mitigate Cd-induced mitochondrial thiol redox impairment.
• The Trx/NTR/NADPH system contributes to redox balance in cotyledons, though coenzyme pools remain vulnerable to oxidative damage.