Researchers from the University of Haifa, the Weizmann Institute and the Center for Genome Regulation (CRG) have constructed the first atlas of all the different cell types of Stylophora pistillata, a stony coral that builds reefs and is native to the oceans Indo-Pacific. Published today in the newspaper Cell, the study is the first to detect the presence of specialized immune cells in corals.
The findings provide new information on the molecular biology and evolution of corals and will aid current and future conservation efforts to protect coral reef ecosystems threatened by rising temperatures and ocean acidification.
The map reveals that Stylophora pistillata has 40 different cell types during the three main stages of their life cycle. Researchers have discovered molecular mechanisms responsible for vital biological processes such as the formation of the coral skeleton, which provides habitat for a large number of marine species. The team also discovered how corals establish a symbiotic relationship with photosynthetic algae that reside in their cells.
The researchers were also surprised to discover the presence of specialized immune cells which employ many genes generally associated with the function of immune cells in vertebrates. Innate immunity was previously thought to play a role in preserving the health of algal symbionts, as well as resistance to rising temperatures and acidification, but so far no specialized immune cells have been found. ‘has been reported in corals.
According to Dr. Tali Mass, one of the study’s authors and researcher at the University of Haifa, “Coral reefs play a vital role in the ecosystem of the oceans and seas, as they provide habitat for about 25 % of animals in the sea and build the world’s largest biogenic structures. Warming seawater and rising acidity pose a threat to the future of coral reefs and therefore the genetic sequencing that we have completed is extremely important for the survival of coral reefs and the future. oceans. “
According to Arnau Sebe Pedrós, co-author of the study and group leader at CRG, “Our work systematically defines the molecular biology of coral cells. This cell atlas will help better understand the responses of corals to rising temperatures and ocean acidification, and could even potentially help design interventions that strengthen the resilience of the coral reefs we have left. This work is also a good example of how single-celled genomics technologies are revolutionizing our understanding of animal biodiversity and its evolution, by bridging the gap between genomes and organisms. “
The researchers built the cell atlas using a method called unicellular RNA sequencing to measure the gene expression of each individual cell. In research, single-celled RNA sequencing is almost exclusively limited to species that can be grown under laboratory conditions. As stony corals are difficult to grow under laboratory conditions, Israeli researchers collected corals at different stages of their life cycle in the Gulf of Eilat and then transported them to the Weizmann Institute and CRG Barcelona. for sequencing and analysis. The study is one of the few to perform a single-cell analysis of wild-collected species.
Stony corals are the staple species of many coral reefs. They start their life as a swimming larva which disperses and settles like a polyp. Polyps quickly build a protein-rich matrix that forms a calcium carbonate skeleton, eventually becoming a colonial adult made up of many individual polys. Colonies of stony corals are the primary habitat for a great diversity of marine species, which is why coral reefs are considered the tropical forests of the sea.
Stony corals live in tropical seas by forming a symbiotic relationship with the photosynthetic algae that live in their cells. Algae provide photosynthetic products to the cell, which in turn provides the algae with carbon. The symbiotic relationship supports the high energy requirements of coral growth and reproduction, including the production of its skeleton.
Over the past decades, coral reefs have declined around the world. The main factors behind this decline are rising ocean temperatures and acidification, which have a direct impact on coral symbiosis by leading to coral bleaching, where corals expel algae living in their tissues, and affect formation. of the skeleton by reducing the rates of calcification.
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