HILIC-MS Metabolomics of Sunflower Senescence

Leaf senescence (the natural aging and dying process of leaves) is controlled by a combination of genetic factors and environmental conditions. As leaves age, their internal structures break down, and the green pigment chlorophyll is lost. At the same time, complex molecules are broken down into simpler ones that can be transported to other parts of the plant, such as seeds, in a process known as nutrient remobilization. This process affects both seed yield and protein content by reducing the plant's ability to photosynthesize while redirecting nutrients elsewhere. Understanding senescence is also important from an agricultural standpoint, as it could help improve how efficiently plants use nitrogen.

Researchers have already explored how senescence in sunflowers interacts with water stress and the use of cover crops from a farming perspective. Building on this, researchers took a deeper look at this interaction at the molecular level by comparing physical characteristics, biochemical responses, gene activity, and metabolic profiles in two closely related sunflower varieties that differ in a region of their DNA linked to senescence. The metabolic profiles of 69 samples were analyzed using a liquid chromatography mass spectrometry (LC-MS) approach in hydrophilic interaction chromatography (HILIC) mode. A paper based on this research was published in the journal BMC Plant Biology.¹

Why Does Leaf Senescence in Sunflower Matter, and What Do We Know About It So Far?

Sunflower is the fourth most widely grown oil crop in the world. It is well suited to warm and semi-arid climates, thriving with relatively little water, nitrogen, and pesticide inputs.²In sunflower, leaf senescence sets in rapidly after flowering. This limits the plant's ability to maintain green, photosynthetically active leaves during the critical period when seeds are filling and developing, which can significantly reduce yield. For this reason, researchers have in recent years begun investigating the molecular processes behind leaf senescence in sunflower by analyzing gene activity and metabolic profiles.^3,4Genetic studies have also been carried out to identify regions of the sunflower genome linked to senescence, but as of yet no specific gene has been pinpointed as responsible. Additionally, because sunflower adapts well to environmentally friendly farming practices, researchers have explored how senescence interacts with water stress and the use of cover crops, though this has so far only been examined from a practical farming perspective rather than at the molecular level.^5-7

What Did the Study Find About Leaf Senescence, Drought Response, and Seed Protein Content in Sunflower?

This study revealed several new findings about how sunflowers respond to drought, including an overall reduction in certain protective compounds and the involvement of some lesser-known molecules with potential antioxidant properties. When examining the specific DNA region linked to senescence, the researchers found that it likely works through a gene involved in breaking down chlorophyll. This region also influenced the protein content of seeds; the version associated with earlier senescence led to lower seed protein, while the other version had the opposite effect. Cover crops had little influence on the molecular profiles observed, and no combined effects were found between drought and the senescence-related DNA region.¹

The researchers report that this is the first time a genetic region linked to leaf senescence has been characterized in sunflower. Importantly, this region also influences seed protein content and appears to be unaffected by drought, which could make it particularly valuable for plant breeding programs. However, more research is needed to determine whether the delayed senescence observed truly benefits the plant's productivity or is simply a visual trait with no functional advantage.¹

References

1. Moroldo, M.; Blanchet, N.; Pouilly, N. et al. Molecular and Physiological Characterization of Two Sunflower Near-Isogenic Lines with Contrasting Haplotypes for Leaf Senescence. BMC Plant Biol. 2026.DOI: 10.1186/s12870-026-09110-8
2. Debaeke, P.; Casadebaig, P.; Flenet, F. et al. Sunflower Crop and Climate Change: Vulnerability, Adaptation, and Mitigation Potential from Case-Studies in Europe. OCL 2017, 24 (3). DOI: 10.1051/ocl/2016052
3. Moschen, S.; Marino, J.; Nicosia, S. et al. Exploring Gene Networks in Two Sunflower Lines with Contrasting Leaf Senescence Phenotype Using a System Biology Approach. BMC Plant Biol. 2019, 19 (1). DOI: 10.1186/s12870-019-2021-6
4. Moschen, S.; Luoni, S. B.; Rienzo, J. A. D. et al. Integrating Transcriptomic and Metabolomic Analysis to Understand Natural Leaf Senescence in Sunflower. Plant Biotech. J. 2016, 14 (2), 719–734. DOI: 10.1111/pbi.12422
5. Bonnafous, F. Prise en compte d’informations a priori en sélection génomique dans un dispositif d’hybrides de tournesol (Helianthus annuus L.). 2017.
6. Souques, L.; Langlade, N. B.; Debaeke, P. et al. Phenotypic Traits of Sunflower Varieties Depend on the Composition of Cover Crops. Field Crops Research. 2025 Feb 1;321:109692. DOI: 10.1016/j.fcr.2024.109692
7. Souques, L.; Alletto, L.; Blanchet, N. et al. Cover Crop Residues Mitigate Impacts of Water Deficit on Sunflower During Vegetative Growth with Varietal Differences, but Not During Seed Development. Eur. J. Agron. 2024, 155, 127139. DOI:10.1016/j.eja.2024.127139