A research team from the Indian Institute of Technology Gandhinagar (IITGN), working with the Indian Council of Agricultural Research–Directorate of Rapeseed-Mustard Research (ICAR-DRMR) in Bharatpur, has mapped and functionally tested the genes that govern self-rejection in two commercially significant Indian varieties of Brassica rapa, the oilseed plants known as toria and yellow sarson. The study, published in Frontiers in Plant Science, combines classical pollination experiments with cutting-edge artificial intelligence-based protein structure prediction to characterise the four major genes that act as the sensors, processors and executors of the self-rejection response. The findings provide what the researchers describe as a molecular blueprint that plant breeders could use to produce high-yielding hybrid mustard at scale.

The stakes are considerable. India imports more than half of its edible oil, a dependence that met roughly 56 percent of domestic demand in 2023–24, leaving both farmers and households exposed to volatile global prices. The Government of India has made edible oil self-reliance a national priority through the National Mission on Edible Oils – Oilseeds, and hybrid varieties — which typically outyield their inbred parents by exploiting hybrid vigour — are central to that strategy. Yet producing hybrid seed commercially requires precise control over pollination, and that is precisely where the plant’s own self-rejection machinery becomes an asset rather than a curiosity.

Self-incompatibility is a genetic mechanism found in many flowering plants that forces cross-breeding. By refusing to accept their own pollen, plants avoid inbreeding, maintain genetic diversity and generate offspring that are often hardier and more productive than either parent. For breeders, a reliable self-incompatibility system is a gift: it spares them the tedium of manually emasculating thousands of flowers to prevent self-pollination, while ensuring that the seed they harvest is genuinely hybrid. The difficulty, until now, has been that while the molecular basis of self-incompatibility has been extensively studied in Brassica napus — the species that includes canola — it remained poorly characterised in India’s commercially grown Brassica rapa varieties.

“To maximise crop yields through hybridisation, we need precise control over pollination, which is aided by self-rejection,” said Dr Subramanian Sankaranarayanan, the study’s corresponding author and Assistant Professor at IITGN’s Department of Biological Sciences and Engineering. “Though SI has been extensively studied in Brassica napus (canola), the molecular basis of this mechanism is poorly characterised in India’s commercially grown Brassica rapa varieties, toria and yellow sarson.” The two varieties offered the team a natural contrast: toria rejects its own pollen and is therefore self-incompatible, while yellow sarson readily accepts it and is self-compatible. Comparing the two allowed the researchers to isolate the molecular machinery responsible for the difference.

The team, which included co-first authors Hemal Bhalla and Kumari Ankita along with colleagues Aman Ahlawat and Surabhi S Rode, began with controlled pollination experiments to establish the compatibility relationships between the varieties. By analysing pollen attachment, pollen tube growth and seed development, they confirmed the expected pattern: in self-pollinated toria, almost nothing grew, while in crosses between the two varieties the flowers filled with growing pollen tubes. With the phenotypes established, the researchers turned to the molecular level, focusing on four genes — SRK, FER1, MLPK and ARC1 — that code for proteins acting as the cellular sensors, processors and executors of the self-rejection response.

The team cloned and sequenced these genes and compared their genetic codes with those of related plants to build family trees, confirming that they were genuine, well-conserved versions of known self-rejection genes rather than lookalikes. Because a gene’s function depends on the three-dimensional shape of the protein it produces, the researchers then modelled those shapes using AlphaFold3, an artificial intelligence tool developed by Google DeepMind and Isomorphic Labs that predicts protein structures from amino acid sequence. The structural analyses revealed that the proteins possess conserved functional domains consistent with their roles in pollen recognition and signalling — effectively a detailed blueprint of each molecular machine, allowing the team to verify that every protein carried the right working parts for its expected job.

Structure alone, however, does not prove function, so the researchers took the crucial step of temporarily silencing each gene one at a time. They used antisense oligonucleotides — short, custom-made strands of synthetic DNA that latch onto a specific gene’s instructions and prevent the cell from acting on them. The strands were simply dripped onto the flower’s stigma, and the silencing was temporary, leaving no permanent genetic change to the plant. The results were striking: when the team muted SRK, FER or ARC1, toria’s self-rejection collapsed and the flower began accepting its own pollen, with fluorescence microscopy confirming robust pollen tube growth that proved the self-incompatibility barrier had been breached.

The study also produced a surprise regarding MLPK. “Traditionally, this gene is considered vital to the self-rejection pathway in related mustard species,” explained Hemal Bhalla, co-first author and a PhD scholar at IITGN’s Department of Biological Sciences and Engineering. “But, in toria, switching off MLPK only partially weakened the rejection response, indicating it plays a secondary or redundant role in this specific variety.” The researchers also uncovered a second line of defence operating on the stigma surface. Within minutes of an incompatible pollen grain landing, the plant deploys a localised chemical shield of reactive oxygen species (ROS) — reactive molecules that halt pollen germination — which the team measured using Nitro Blue Tetrazolium, a dye that darkens wherever these molecules gather. Silencing SRK, FER or MLPK dulled the ROS release, while silencing ARC1 did not, suggesting the flower runs two separate defence systems simultaneously, with ARC1 likely operating through an alternative cellular degradation pathway to neutralise unwanted pollen.

The researchers showed that these genes are highly conserved across Brassica species, indicating that the underlying molecular mechanism has remained largely unchanged over evolutionary time — good news for breeders hoping that findings in one variety will translate to others. The authors emphasise that their work establishes a foundation, with permanent gene editing, transgenic validation and technology commercialisation remaining future steps. Encouragingly, cross-tests confirmed that toria and yellow sarson still interbreed successfully, with the resulting seeds showing near-complete germination, an important signal that the system is usable in real breeding programmes. “Our findings provide a clear molecular blueprint of how pollination is governed in India’s oilseed varieties,” noted Kumari Ankita, co-first author and a PhD scholar at IITGN. “Foundational genetics like this creates an execution pipeline for developing hybrids that are stacked with favourable traits, including higher oil content, disease resistance, and resilience to erratic weather.” As climate change brings erratic monsoons, unseasonal heatwaves and shifting pest pressures to the subcontinent, the ability to breed hardier oilseeds quickly has taken on real economic weight — and a plant’s ancient refusal to pollinate itself may prove to be one of India’s most valuable agricultural tools. The research was supported by fellowships and grants from IITGN and the Government of India, including the Prime Minister Research Fellowship, the University Grants Commission, the Department of Biotechnology and the Science and Engineering Research Board.

Subject of Research: Characterization of self-incompatibility genes in Brassica rapa varieties toria and yellow sarson to support hybrid oilseed breeding in India

Article Title: How a plant’s refusal to self-pollinate could help India grow more of its own cooking oil

Article References: How a plant’s refusal to self-pollinate could help India grow more of its own cooking oil. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: self-incompatibility, Brassica rapa, toria, yellow sarson, mustard, hybrid breeding, edible oil, SRK, ARC1, AlphaFold3, reactive oxygen species, India

Lipid oxidation is one of the chief enemies of food quality. When unsaturated fatty acids react with oxygen, they form hydroperoxides, aldehydes, and a cascade of secondary products that ruin flavor, erode nutritional value, and raise safety concerns. Two measurements dominate the monitoring of this decay: the peroxide value, which tracks the early stage of peroxidation, and malondialdehyde, or MDA, a hallmark of advanced oxidative chain-scission. Photooxidation, in which light energizes the process, is among the most damaging pathways, yet the precise role of heme proteins in accelerating it has remained surprisingly underexplored.

The research team, led by Mahdi Hajimohammadi of Kharazmi University in collaboration with colleagues in Iran and Iraq, set out to close that gap. Rather than isolating purified hemoglobin, they used intact erythrocyte suspensions derived from commercially supplied sheep blood, preserving the protein’s native structure and redox environment. This choice made the system biologically realistic: hemoglobin remained embedded in the matrix it normally occupies, at the boundary between an aqueous phase and the oil droplets of a commercial canola oil emulsion. The mixture was illuminated by a solar simulator, an array of 276 LED lamps spanning 380 to 780 nanometers and delivering an intensity of roughly 59,660 lux, closely matching the spectrum of natural sunlight.

The results were striking. After 2.5 hours of irradiation in the presence of air, the peroxide value of the oil climbed to 9.7 milliequivalents of oxygen per kilogram, while control experiments kept in the dark, lacking hemoglobin, or starved of oxygen showed only trace oxidation. The conclusion was unambiguous: hemoglobin, oxygen, and light must all be present simultaneously for the reaction to proceed efficiently. Under true sunlight, the peroxide value reached an even higher 10.5, confirming that the laboratory simulator faithfully reproduces the outdoor process. Spectroscopic monitoring of the heme’s characteristic Soret absorption band at 407 nanometers revealed a 69.8 percent decline over extended irradiation, evidence that the photosensitizer itself is progressively degraded as it works.

To dissect the mechanism, the researchers deployed chemical scavengers as molecular interrogators. Adding butylated hydroxytoluene, a potent free-radical quencher, cut the peroxide value to 3.8, implicating carbon-centered radicals generated by hydrogen abstraction. Adding sodium azide, a classic singlet oxygen scavenger, suppressed oxidation even further, to 3.1, demonstrating that singlet oxygen, an excited and highly reactive form of molecular oxygen, is a major player. Both pathways operate at once, which helps explain why hemoglobin outperformed two benchmark oxidants: the dye Rose Bengal, a selective singlet oxygen generator that achieved a peroxide value of only 6.8, and potassium permanganate, a classical chemical oxidant that managed just 2.1 under comparable conditions.

Proton nuclear magnetic resonance spectroscopy provided product-level confirmation of the damage. Signals from vinylic protons on the oil’s carbon-carbon double bonds, at chemical shifts of 5.2 to 5.4 parts per million, fell by 31.2 percent, consistent with singlet oxygen attacking double bonds through ene reactions. Bis-allylic protons, at 2.7 to 2.8 parts per million, declined even more sharply, by 36.9 percent, a signature of radical-mediated hydrogen abstraction at the most vulnerable positions of polyunsaturated fatty acids. A new aldehydic resonance near 9.5 parts per million announced the formation of MDA, the definitive marker of advanced peroxidation and chain scission. Perturbations in the glycerol proton region around 4.1 parts per million suggested that radical-driven beta-scission was even cleaving the ester bonds of the triglyceride backbone, fragmenting the oil into smaller, more polar molecules.

An independent probe sealed the case for singlet oxygen. Anthracene, a compound that reacts selectively with singlet oxygen to form a colorless endoperoxide, lost roughly 33 percent of its absorbance at 375 nanometers after four hours of irradiation in the hemoglobin-oil system, and sodium azide largely halted the bleaching. The solvent experiments added a subtle layer of physical chemistry: oxidation efficiency followed the order acetonitrile, ethanol, acetone, methanol, then dimethyl sulfoxide, mirroring the known lifetimes of singlet oxygen in these media, which range from about 65 microseconds in acetonitrile down to 19 microseconds in DMSO. Highly coordinating solvents like DMSO may also interfere with the formation of ferryl heme intermediates, the high-valent iron-oxo species suspected of driving the radical pathway.

That ferryl pathway remains the tentative half of the mechanism. The authors are careful to note that they did not directly observe the ferryl species, hemoglobin iron in the +4 oxidation state bound to oxygen. Its involvement is inferred from indirect evidence: the suppressive effect of the radical scavenger BHT, the preferential depletion of bis-allylic protons, and the damping effect of DMSO. Previous work on related metalloporphyrin and hemoglobin systems has detected ferryl intermediates spectroscopically, lending plausibility to the interpretation, but direct confirmation in this food system awaits future study. Even so, the combined evidence supports a dual oxidative engine: singlet oxygen generated by energy transfer from the light-excited heme, working in parallel with a heme-iron radical chemistry that abstracts hydrogen from the lipid chains.

The implications stretch well beyond the shelf life of bottled oil. Hemoglobin is abundant, biodegradable, and essentially free, recovered as a by-product of meat processing that would otherwise be discarded. The study’s preliminary results suggest that this waste protein could be harnessed as a low-cost photosensitizer for sunlight-driven degradation of lipid-rich effluents from edible oil processing, replacing ozonation and Fenton treatments that demand harsh chemical oxidants and energy-intensive conditions. The authors caution that real industrial wastewater, long-term protein stability under continuous illumination, light penetration, oxygen transfer, and reactor scale-up all remain to be tested. Still, the vision is compelling: a circular food system in which blood from the slaughterhouse becomes a solar-powered catalyst for cleaning the oil industry’s dirtiest water, while simultaneously teaching food scientists exactly how to keep light and heme apart to protect the products on our shelves.

Subject of Research: Hemoglobin-mediated sunlight-induced lipid oxidation in edible oils and its potential for sustainable wastewater treatment

Article Title: Sunlight‐Induced Lipid Oxidation and Degradation of Edible Oil Mediated by Hemoglobin: Implications for Food System Sustainability

Article References: Hajimohammadi, M., Faraj, F. H., Boghdachi, M., Alwasiti, A. A., & Shnain, Z. Y. (2026). Sunlight‐Induced Lipid Oxidation and Degradation of Edible Oil Mediated by Hemoglobin: Implications for Food System Sustainability. Food Science & Nutrition, 14(10), Article e72423. https://doi.org/10.1002/fsn3.72423

Image Credits: AI Generated

DOI: 10.1002/fsn3.72423

Keywords: hemoglobin, lipid oxidation, singlet oxygen, edible oil, photosensitizer, photooxidation, malondialdehyde, ferryl heme, food science, wastewater treatment, circular economy, sunlight