The gene, named HbRbohD, encodes a membrane-localized enzyme that triggers stress-responsive ROS signaling while simultaneously enhancing antioxidant protection. Through molecular, cellular, and transgenic analyses, the study demonstrates that HbRbohD strengthens resistance to fungal pathogens and improves tolerance to salt and osmotic stress.
Crop plants are constantly exposed to pathogens, salinity, drought, and other stresses that threaten productivity. One of the earliest cellular reactions to stress is an “oxidative burst,” a rapid increase in ROS. In plants, this burst is primarily driven by respiratory burst oxidase homologs (Rbohs), membrane-bound enzymes that generate ROS using NADPH. Among these, RbohD has emerged as a master regulator in many species, integrating signals from pathogen recognition, hormones, and environmental cues. While RbohD has been extensively studied in model plants, its role in economically important crops—such as the rubber tree, the sole commercial source of natural rubber—has remained unclear. Understanding how rubber trees manage ROS could open new avenues to protect yields under increasing stress pressure.
A study (DOI: 10.48130/tp-0025-0029) published in Tropical Plants on 13 November 2025 by Hongli Luo’s team, Hainan University, reveals how plants maintain ROS homeostasis under adverse conditions and provide new insight into stress adaptation mechanisms in rubber trees and other crops.
Using a combination of bioinformatic screening, molecular cloning, expression profiling, cellular imaging, and transgenic functional assays, the researchers systematically investigated the role of HbRbohD in plant stress responses. First, the Arabidopsis AtRbohD sequence was used as a query in BlastX searches to identify a homolog in rubber tree, followed by RT-PCR amplification and sequencing to confirm the full-length coding sequence. This approach revealed that HbRbohD encodes a 910–amino acid NADPH oxidase containing conserved NADPH_Ox, EF-hand, and NAD-binding domains, and phylogenetic analysis placed it in the same clade as AtRbohD, confirming its orthology. To predict regulatory potential, promoter cis-elements within 3 kb upstream of the gene were analyzed in silico, uncovering multiple stress- and hormone-responsive motifs associated with biotic stress, salinity, temperature, and phytohormone signaling. Guided by these predictions, expression analyses were conducted under pathogen infection, abiotic stress, and hormone treatments, showing that HbRbohD was strongly induced by fungal pathogens, immune elicitors, salt stress, and several phytohormones, with particularly strong responsiveness to salicylic acid. Subcellular localization was then examined by transiently expressing an HbRbohD–GFP fusion in tobacco leaves, which demonstrated exclusive plasma membrane localization. Consistent with its predicted enzymatic role, ROS production was quantified in rubber tree protoplasts using DCFH-DA staining, revealing a marked increase in ROS accumulation upon HbRbohD overexpression. To assess biological function, transgenic Arabidopsis plants overexpressing HbRbohD were generated and evaluated for stress tolerance. These plants exhibited enhanced resistance to necrotrophic fungal pathogens and significantly improved seed germination under salt and osmotic stress. Further transcript analysis showed elevated expression of pattern-triggered immunity and salicylic acid pathway genes, while biochemical assays revealed increased activities of antioxidant enzymes and reduced lipid peroxidation. Together, these results demonstrate that HbRbohD integrates ROS production with antioxidant regulation to enhance plant defense and stress tolerance.
The findings position HbRbohD as a promising molecular target for improving stress resilience. By reinforcing both immune signaling and antioxidant capacity, this gene could help crops better withstand pathogens and salinity—two major constraints on agricultural productivity. In rubber trees, such mechanisms may contribute directly to stabilizing latex yield under challenging field conditions.
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References
DOI
Original Source URL
https://doi.org/10.48130/tp-0025-0029
Funding information
This work was supported by the Hainan Provincial Natural Science Foundation of China (352RC649), and the National Natural Science Foundation of China (32260716).
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.