Format: ORAL

Wen-Jing Wang1, Hong-Fan Chen1,2, Yue Gao1, Hong Liao1, Jian-Li Zhao1,*

1 Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China, Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming, 650504, Yunnan, China 2 Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650504, Yunnan, China

Premise: Nectar serves as a reward offered by flowers to pollinators, facilitating the success of sexual reproduction. Consequently, nectar holds indispensable biological significance in plant reproduction and evolution. Despite the characterization of nectar function and composition, the mechanism of nectar secretion has remained unclear. Methods: To elucidate the probable mechanisms governing nectar secretion, we selected two Roscoea species as model: the outcrossing species R. cautleoides, secreting nectar from its nectaries, and the autonomous selfing species R. schneideriana, no nectar. We first conducted a comparative study for microstructure, nectary size and nectar volume were recorded in the field. Nectary location, external form and internal structure were observed by paraffin section staining method. Subsequently, we performed an intricate assembly and annotation of the R. cautleoides genome, employing multi-omics techniques, facilitating an analysis of the molecular mechanisms in the nectaries and doing identification of target genes crucial for nectar secretion. Ultimately, we delved into the gene structure, function and evolution of these essential genes. Results: Here, we found that the nectaries of R. schneideriana possess significantly reduced volume and deteriorated internal structures, compared to R. cautleoides. Multi-omics correlation analysis identified one gene that is specifically highly expressed in the nectaries of the R. cautleoides, which is critical for nectar secretion in Roscoea. Conclusions: These results provide an important basis for revealing the differences of floral characteristics, pollination mechanism and breeding system, as well as the mechanism of nectar secretion between outcrossing and selfing species in Roscoea. Characterization of this target gene regulating nectary production has provided new insights into understanding of the mechanism and evolution of nectar secretion in plants.