How mango fruits fight UV-induced oxidative damage

By systematically mapping and analyzing the ascorbate peroxidase (APX) gene family in mango, researchers reveal how specific genes are switched on to detoxify harmful reactive oxygen species (ROS).

Mango is one of the world’s most important tropical fruit crops, valued for its nutritional richness and economic significance. However, mango cultivation is increasingly challenged by abiotic stresses such as drought, high temperature, salinity, intense light, and UV-B radiation. UV-B exposure, linked to ozone layer depletion, disrupts plant growth and fruit development by triggering excessive production of ROS, including hydrogen peroxide and superoxide radicals. These molecules damage membranes, proteins, and DNA if not tightly controlled. To survive, plants rely on antioxidant defense systems that maintain redox balance. Among these defenses, APX plays a central role by converting toxic hydrogen peroxide into water using ascorbate as an electron donor. Despite its importance in many plant species, the APX gene family in mango has remained poorly characterized, limiting efforts to harness this pathway for crop improvement.

A study (DOI: 10.48130/tp-0025-0032) published in Tropical Plants on 22 December 2025 by Kaibing Zhou’s team, Hainan University, provides a molecular framework for understanding how the MiAPX gene family contributes to oxidative stress defense and UV-B tolerance in mango, offering valuable targets for developing stress-resilient cultivars.

Using a genome-wide identification and annotation strategy, ten ascorbate peroxidase genes were identified in the mango genome and designated MiAPX1–MiAPX10, followed by systematic characterization of their physicochemical properties. The results revealed substantial diversity within the MiAPX family: protein lengths ranged from 240 to 621 amino acids, with MiAPX8 encoding the smallest and MiAPX9 the largest protein, corresponding to molecular weights of approximately 26.4–69.3 kDa. Six proteins were acidic and four were basic; eight were predicted to be stable, and all exhibited negative GRAVY values, indicating predominantly hydrophilic properties. Secondary-structure prediction using SOPMA showed variable proportions of α-helices (32.72–43.71%), extended strands (9.09–12.60%), β-turns (2.77–5.78%), and random coils (41.87–54.95%), suggesting structural flexibility and functional divergence among MiAPX proteins. To further link sequence features with spatial conformation, three-dimensional models were generated using SWISS-MODEL, revealing that all MiAPX proteins were predicted monomers with generally high model quality (GMQE 0.79–0.97), particularly for MiAPX3, MiAPX4, MiAPX5, MiAPX6, MiAPX7, and MiAPX9. Conserved motif analysis using MEME identified ten motifs across the gene family, with motif 3 present in all MiAPX members, while domain analysis confirmed that all proteins belong to the plant peroxidase-like superfamily, highlighting functional conservation. Gene structure analysis showed that nine MiAPX genes contained two introns, whereas MiAPX8 exhibited a distinct exon–intron organization, suggesting possible functional specialization. Chromosomal mapping revealed uneven distribution across nine chromosomes, and duplication analysis indicated that segmental duplication was the primary driver of gene family expansion. All duplicated gene pairs displayed Ka/Ks ratios below 1, indicating strong purifying selection. Phylogenetic and synteny analyses with Arabidopsis thaliana and rice grouped APX genes into four clusters and identified close evolutionary relationships, such as MiAPX9–AtAPX8, MiAPX5–AtAPX2, and MiAPX10–AtAPX6. Finally, transcriptomic and qRT-PCR analyses demonstrated that several MiAPX genes were significantly upregulated under UV-B stress at different developmental stages, whereas MiAPX8 was consistently downregulated, highlighting functional divergence within the family and implicating specific MiAPX members in UV-B–induced oxidative stress responses in mango fruit.

The results provide valuable targets for breeding and biotechnology aimed at enhancing stress tolerance in mango. By identifying which APX genes are most responsive to UV-B stress, the study lays the groundwork for selecting molecular markers or engineering antioxidant pathways to stabilize fruit quality under environmental pressure.

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References

DOI

10.48130/tp-0025-0032

Original Source URL

https://doi.org/10.48130/tp-0025-0032

Funding information

This work was financially supported by the National Natural Science Foundation of China (Grant No. 32160677) and the Hainan University Mango Research System.

About Tropical Plants

Tropical Plants (e-ISSN 2833-9851) is the official journal of Hainan University and published by Maximum Academic Press. Tropical Plants undergoes rigorous peer review and is published in open-access format to enable swift dissemination of research findings, facilitate exchange of academic knowledge and encourage academic discourse on innovative technologies and issues emerging in tropical plant research.