Morphological, biochemical, molecular and ultrastructural changes induced by Cd toxicity in seedlings of Theobroma...

Area of Science:

• Plant Science
• Environmental Toxicology
• Molecular Biology

Background:

• Cadmium (Cd) is a toxic heavy metal pollutant.
• Understanding plant responses to heavy metal stress is crucial for agriculture and environmental remediation.
• Theobroma cacao (cocoa) is an economically important crop susceptible to soil contaminants.

Purpose of the Study:

• To investigate the morphological, biochemical, and molecular responses of two Theobroma cacao progenies to cadmium (Cd) stress.
• To compare the tolerance mechanisms of 'Catongo'×'Catongo' and CCN-10×SCA-6 progenies under Cd exposure.
• To identify key genes and pathways involved in Cd tolerance in cocoa.

Main Methods:

• Seeds of two T. cacao progenies were treated with varying concentrations of Cd solutions.
• Seedlings were grown in a greenhouse for 60 days, and various analyses were performed.
• Morphological changes, chloroplast and nuclear structure, epidermal thickness, enzyme activity (guaiacol peroxidase), gene expression (PCS-1, PER-1, MT2b, Cu-Zn SODCyt), and Cd accumulation were assessed.

Main Results:

• Cadmium exposure induced morphological changes, including chloroplast deformation and reduced tissue thickness in both progenies.
• CCN-10×SCA-6 showed increased guaiacol peroxidase activity and higher expression of stress-related genes (PCS-1, PER-1, MT2b).
• 'Catongo'×'Catongo' also exhibited increased gene expression but accumulated more Cd and showed reduced Zn and Fe levels, indicating lower tolerance.

Conclusions:

• The CCN-10×SCA-6 progeny demonstrated superior tolerance to Cd stress compared to 'Catongo'×'Catongo' due to distinct survival strategies.
• Differential gene expression and enzyme activity play a significant role in mediating Cd tolerance in T. cacao.
• Cadmium stress negatively impacts essential nutrient levels (Zn, Fe) in cocoa seedlings.