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Plant and Soil· 2026Q1

Molecular and physiological mechanisms of the cadmium response in seedlings of two Theobroma cacao L. genotypes

Paola Delgadillo-Durán, Francisco Miguel Menéndez-Burns, Caren Rodriguez‐Medina, Andrea C. Montenegro et al.

Short summary

Cacao seedlings exposed to cadmium (Cd) exhibit genotype-specific molecular and physiological responses, with high-accumulating genotypes showing reduced stomatal conductance and increased abscisic acid (ABA) levels, suggesting an ABA-mediated signaling pathway limits Cd uptake.

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Key points

  • Cacao genotypes PA121 (low-accumulator) and TSH660 (high-accumulator) were exposed to 0 and 10 ppm Cd.
  • High-accumulator seedlings showed reduced stomatal conductance (Gs) and increased root ABA concentrations under Cd stress.
  • Gene expression analysis revealed genotype-specific changes in detoxification, ROS, and hormone metabolism, particularly ABA-related genes.
  • Roots of the high-accumulator genotype exhibited downregulation of Cd transport genes (ZIP/IRT, NRAMP, HMA5 orthologs).

AI-generated from the title and abstract; the full text is not read.

Abstract

Abstract Aims Understanding the mechanisms of cadmium (Cd) accumulation in cacao plants is critical to mitigating health risks associated with Cd exposure through chocolate consumption. A general and genotype-specific molecular and physiological responses were characterized. Methods Seedlings of cacao genotypes PA121 and TSH660 were exposed to 0 and 10 ppm Cd in hydroponic conditions. Samples were collected at 0, 24, and 48 h (RNAseq) and at 60 days post-treatment (ICP-OES). Gene expression profiles were compared using differential gene expression (DEG) and gene ontology analyses. Gas exchange (Gs) and abscisic acid (ABA) measurements were conducted on greenhouse-grown PA121 seedlings. Results Both shared and genotype-specific changes were observed in genes associated with detoxification, ROS, and hormone metabolism, notably ABA-related genes. In leaves, the low-accumulator exhibited fewer DEGs than the high-accumulator, whereas in roots, both genotypes displayed similar expression profiles. The high-accumulating genotype exhibited fewer statistically significant expression changes in key hormone biosynthesis genes. In roots, Cd transport family genes, including ZIP/IRT and NRAMP, were downregulated. The high-accumulator genotype exhibited significant downregulation of one ZIP and one HMA5 ortholog, whereas the response of the low-accumulator genotype included upregulation of a different HMA5 ortholog. Additionally, high-accumulator seedlings exposed to 12 ppm Cd reduced Gs without significant changes in photosynthesis, while ABA concentrations increased in roots at 36 h after Cd exposure. Conclusions Together, these results support a model in which Cd induces ABA-mediated root signaling that reduces stomatal conductance and transpiration-driven mass flow, while suppressing the expression of active Cd transporters, thereby limiting Cd uptake.

The authors' abstract, as published at the source. Plant and Soil, 2026 · DOI ↗

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