The Gentiana rigescens genome and transcriptome for the investigation of flower repetitive blooming.

BACKGROUND

Reversible flower opening and closing is a specialized reproductive strategy to improve plant fitness in response to ambient environmental changes. As a common phenomenon in angiosperm plants, the underlying genetic and molecular mechanisms remain unknown. Previous research shows that this phenomenon is a characteristic feature of the genus Gentiana, and the external environmental cues driving petal movements differ among species. However, due to the interaction among environmental stimuli, limited progress was made in disentangling the responsible signaling pathways and putative molecular regulators.

RESULTS

We identified the alpine species Gentiana rigescens as a model to study repetitive flower opening and closing. Field observations and laboratory investigations confirmed that ambient temperature is the dominant factor driving repetitive flower opening and closing in G. rigescens. We constructed a chromosome-level genome assembly for G. rigescens and performed comparative transcriptomic analyses of flowers under varying natural temperature conditions. Differentially expressed genes revealed Ca2+ channel proteins as candidate temperature sensors. Both transcriptomic and experimental analyses showed that distinct calcium signaling pathways followed by dynamic cell wall modification underlie the repetitive flower blooming at different temperatures. In addition, auxin showed antagonistic effects on flower opening at high temperatures and closing at low temperatures, possibly by affecting the cell wall acidification and the activities of cell wall remodeling enzymes.

CONCLUSIONS

This study provides genetic resources for investigating the temperature-regulated repetitive flower opening and highlights the divergent signaling pathways in controlling reversible flower opening and closing.