Physiological and transcriptomic analysis provide new insight into seed shattering mechanism in Carex breviculmis ‘Siji’

Carex breviculmis is an excellent native grass species of the Carex L. of the Cyperaceae family. It has strong resistance and outstanding water-saving advantages, which is widely used in landscaping and understory ecological management. However, the strong seed shattering affects the seed yield and increases the risk of seed harvesting,which not only enhances the difficulty of seed production,but also limits the large-scale application of C. breviculmis. In order to explore the intrinsic mechanism of seed shattering in C. breviculmis, this study analyzed the histology, physiology, and transcriptomics of C. breviculmisseeds. Through histological observation, it was found that there are obvious abscission zones on the seeds, mainly distributed at the end of the seeds. By measuring the physiological indicators, it was found that the cellulase activity in the abscission zone gradually increased with the development of the spike at different stages, and was significantly positively correlated with the degree of seed shattering. In addition, the changes in the content of gibberellin, cytokinin, and ethylene in the abscission zone were significantly correlated with the breaking tensile strength. The second-generation transcriptome sequencing data of the abscission zone indicate that the main pathways involved in seed shattering include "plant hormone signaling transduction", "phenylalanine biosynthesis", and "starch and sucrose metabolism", and many key genes that may be involved in the seed shattering process have been identified. This study provides new insights into the seed shattering mechanism of C. breviculmis and has important theoretical and practical significance for breeding low seed shattering C. breviculmisvarieties.