The domesticated sunflower, Helianthus annuus L., is a global oil crop that has promise for climate change adaptation, because it can maintain stable yields across a wide variety of environmental conditions, including drought¹. Even greater resilience is achievable through the mining of resistance alleles from compatible wild sunflower relatives^2,3, including numerous extremophile species⁴. Here we report a high-quality reference for the sunflower genome (3.6 gigabases), together with extensive transcriptomic data from vegetative and floral organs. The genome mostly consists of highly similar, related sequences⁵ and required single-molecule real-time sequencing technologies for successful assembly. Genome analyses enabled the reconstruction of the evolutionary history of the Asterids, further establishing the existence of a whole-genome triplication at the base of the Asterids II clade⁶ and a sunflower-specific whole-genome duplication around 29 million years ago⁷. An integrative approach combining quantitative genetics, expression and diversity data permitted development of comprehensive gene networks for two major breeding traits, flowering time and oil metabolism, and revealed new candidate genes in these networks. We found that the genomic architecture of flowering time has been shaped by the most recent whole-genome duplication, which suggests that ancient paralogues can remain in the same regulatory networks for dozens of millions of years. This genome represents a cornerstone for future research programs aiming to exploit genetic diversity to improve biotic and abiotic stress resistance and oil production, while also considering agricultural constraints and human nutritional needs^8,9.

Cluster root formation in white lupin ( Lupinus albus L.) is induced mainly by phosphorus (P) starvation, and seems to be regulated by the endogenou

After-ripening is the mechanism by which dormant seeds become nondormant during their dry storage after harvest. The absence of free water in mature seeds does not allow detectable metabolism; thus, the processes associated with dormancy release under these conditions are largely unknown. We show here that sunflower (Helianthus annuus) seed alleviation of dormancy during after-ripening is associated with mRNA oxidation and that this oxidation is prevented when seeds are maintained dormant. In vitro approaches demonstrate that mRNA oxidation results in artifacts in cDNA–amplified fragment length polymorphim analysis and alters protein translation. The oxidation of transcripts is not random but selective, and, using microarrays, we identified 24 stored mRNAs that became highly oxidized during after-ripening. Oxidized transcripts mainly correspond to genes involved in responses to stress and in cell signaling. Among them, protein phosphatase 2C PPH1, mitogen-activated protein kinase phosphatase 1, and phenyl ammonia lyase 1 were identified. We propose that targeted mRNA oxidation during dry after-ripening of dormant seeds could be a process that governs cell signaling toward germination in the early steps of seed imbibition.

Climate change is characterized by higher temperatures, elevated atmospheric CO2 concentrations, extreme climatic hazards, and less water available for agriculture. Sunflower, a spring-sown crop often cultivated in southern and eastern regions of Europe, could be more vulnerable to the direct effect of heat stress at anthesis and drought during its growing cycle, both factors resulting in severe yield loss, oil content decrease, and fatty acid alterations. Adaptations through breeding (earliness, stress tolerance), crop management (planting dates), and shifting of growing areas could be developed, assessed and combined to partly cope with these negative impacts. New cultivation opportunities could be expected in northern parts of Europe where sunflower is not grown presently and where it could usefully contribute to diversify cereal-based cropping systems. In addition, sunflower crop could participate to the mitigation solution as a low greenhouse gas emitter compared to cereals and oilseed rape. Sunflower crop models should be revised to account for these emerging environmental factors in order to reduce the uncertainties in yield and oil predictions. The future of sunflower in Europe is probably related to its potential adaptation to climate change but also to its competitiveness and attractiveness for food and energy. Le changement climatique se caractérise par des températures élevées, de plus fortes concentrations atmosphériques en CO2, des risques climatiques extrêmes et moins d'eau disponible pour l'agriculture. Le tournesol, culture semée au printemps dans le sud et l'est de l'Europe, pourrait être plus exposé à l'avenir aux fortes températures et à un déficit hydrique marqué dès la floraison, avec pour conséquences des pertes de rendement, une diminution de la teneur en huile et une altération de la composition en acides gras. Des adaptations sont possibles à court et moyen terme par la sélection (précocité, tolérance aux stress), la conduite de culture (date de semis) et le déplacement des zones de production, permettant de faire face en partie aux impacts négatifs attendus. Ainsi le tournesol pourrait être cultivé plus au nord participant utilement à la nécessaire diversification des bassins céréaliers. En outre, la culture de tournesol étant faiblement émettrice de gaz à effet de serre par rapport aux céréales ou au colza pourrait contribuer davantage à la solution climatique apportée par l'agriculture. Les modèles de culture devraient être revus pour mieux tenir compte de ces facteurs environnementaux émergents si l'on veut réduire les incertitudes dans les prédictions de rendement et de teneur en huile. L'avenir du tournesol en Europe est probablement lié à son potentiel d'adaptation au changement climatique, mais dépendra aussi de sa compétitivité et de son attractivité en tant que fournisseur d'énergie et d'aliments.