The gene, named\u00a0HbRbohD, 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.<\/p>\n
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 \u201coxidative burst,\u201d 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\u2014such as the rubber tree, the sole commercial source of natural rubber\u2014has remained unclear. Understanding how rubber trees manage ROS could open new avenues to protect yields under increasing stress pressure.<\/p>\n
A\u00a0study\u00a0(DOI: 10.48130\/tp-0025-0029)<\/a><\/strong>\u00a0published in\u00a0Tropical Plants<\/a><\/strong>\u00a0on\u00a013 November 2025 by Hongli Luo\u2019s team, Hainan University, reveals\u00a0how plants maintain ROS homeostasis under adverse conditions and provide new insight into stress adaptation mechanisms in rubber trees and other crops.<\/p>\n Using a combination of bioinformatic screening, molecular cloning, expression profiling, cellular imaging, and transgenic functional assays, the researchers systematically investigated the role of\u00a0HbRbohD\u00a0in plant stress responses. First, the\u00a0Arabidopsis AtRbohD\u00a0sequence was used as a query in\u00a0BlastX\u00a0searches 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\u00a0HbRbohD\u00a0encodes a 910\u2013amino acid\u00a0NADPH\u00a0oxidase 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\u00a0HbRbohD\u00a0was 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\u2013GFP 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\u00a0HbRbohD\u00a0overexpression. To assess biological function, transgenic Arabidopsis plants overexpressing\u00a0HbRbohD\u00a0were 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.<\/p>\n The findings position\u00a0HbRbohD\u00a0as 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\u2014two major constraints on agricultural productivity. In rubber trees, such mechanisms may contribute directly to stabilizing latex yield under challenging field conditions.<\/p>\n ###<\/p>\n References<\/p>\n DOI<\/strong><\/p>\n 10.48130\/tp-0025-0029<\/a><\/p>\n Original Source URL<\/strong><\/p>\n https:\/\/doi.org\/10.48130\/tp-0025-0029<\/a><\/p>\n Funding information<\/strong><\/p>\n This work was supported by the Hainan Provincial Natural Science Foundation of China (352RC649), and the National Natural Science Foundation of China (32260716).<\/p>\n About\u00a0Tropical Plants<\/a><\/strong><\/p>\n