Scientists unravel the molecular mechanisms behind cystic dormancy in dinoflagellates

The dinoflagellate plexus plays an important role in aquatic ecosystems, particularly as a major contributor to harmful algae flowers. They can enter the dormant stage, known as the resting cystic stage, and survive for a long time (from UP to 150 years) in marine sediments. This dormancy is essential for annual population dynamics, blooming cycles, and geographical expansion.

Despite the ecological importance of cysts at rest, the molecular mechanisms governing the dormantation, survival rate, and germination of natural sediments remain largely unexplored.

To better understand this process, researchers from the Institute of Oceanography at the Chinese Academy of Sciences (IOCAS) have investigated these mechanisms in collaboration with scientists at the University of Connecticut. They utilized dinoflagellate mRNA-specific splicing readers as “hooks” along with real-time sequencing of single molecules and other physiological measurements.

The study was published in Science Advances on February 7th.

The researchers have constructed three cDNA libraries based on the wishes of field cyst communities to reveal the genetic and metabolic mechanisms involved in cyst dormancy. They found that, except those associated with photosynthetic pathways, the majority of genes associated with major metabolic and regulatory pathways remain transcriptionally active in cystic community.

Additionally, the researchers have identified “active” genes and pathways that are important for maintaining the survival and potential for germination of dinoflagellate sporangiocysts buried in marine sediments.

“The extensive active metabolic landscape observed in cystic assemblies embedded with sediment highlights important aspects of the molecular machinery required to maintain cyst dormant,” says the corresponding authors of the study. Professor Tan Inzon explained.

Through metatranscriptome analysis and subsequent hypotheses, the researchers gained deeper insights by examining laboratory-induced cysts in representative cyst-producing terrifying lagellate species. They found increased autophagy during cyst dormancy, suggesting that alternative energy generation and recycling of cellular resources are important strategies for maintaining dormancy and survival.

Furthermore, the researchers found that two classic plant hormones, abscisic acid (ABA) and giberellic acid (GA)) have an antagonistic role in regulating dormant maintenance and release of cysts . This study demonstrated that cold temperature and darkness, which are usually signals of two environments present in marine sediments, induce opposing effects on ABA and GA biosynthesis and catabolism. This increases levels of ABA, reduces GA accumulation, and responds to deep dormantation of the terrifying cyst in the natural environment.

This study enhances understanding of the molecular mechanisms underlying life-cycle transitions and dormancy in swirl plants.