Mounting of erratic histoincompatible responses in hermatypic corals: a multi-year interval comparison.

Studies on allorecognition in the phylum Cnidaria have disclosed complex arrays of effector mechanisms, specificity and competency to distinguish precisely between self and non-self attributes, and have revealed the existence of allogeneic maturity. Here we studied allo-responses between young Stylophora pistillata colonies by following 517 allogeneic interactions between naturally settled kin aggregates and by establishing 417 forced allogeneic and autogeneic assays made of solitarily settled spat that were cut into two similar size subclones, of which one had been challenged allogeneically. Fused assays were exposed to a second allorecognition challenge, made of three allogeneic types. Whereas about half of the kin allogeneic interactions led to tissue fusions and chimera formations, none of the 83 non-sibling pair combinations were histocompatible. In contrast to previous results we recorded rejections between siblings at the age of less than two months. More challenging, we documented cases of fusions between interacting siblings at ages older than one-year-old partners, all differing from a previous study made on the same coral population more than a decade ago. Similar erratic histoincompatible responses were recorded in other pocilloporid species. We suggest that these results reflect reduced genetic heterogeneity caused by chronic anthropogenic impacts on shallow water coral populations where planulae originating from the same mother colony or from different mother colonies that are genetically related share increasing parts of their genomes. Offspring born to related parents may also reveal an increase in genomic homozygosity, and altogether impose erratic alloimmunity.

Assembled catalog of immune-related genes from allogeneic challenged corals that unveils the participation of vWF-like transcript.

While reef-building corals portray highly complex and specific allorecognition responses, still, no available synthesis on historecognition at the molecular level exists for this group of organisms. Here, we present the first subtractive library of expressed sequence tags (ESTs) from allogeneic challenged coral (Stylophora pistillata) colonies revealing the differential expression of a wide range of immune-related genes. 1760 unique ESTs were clustered and assembled into 230 contigs and 1530 singlets with 28% that showed homology (E-value < or =0.005) to known database sequences, of which 16% (n=80) homologues were identified as immune-relevant genes, encoding for stress proteins, pattern recognition receptors and complement proteins, proteases, cell adhesion proteins, cytokine related proteins, programmed cell death and proteasome-associated proteins. Transcripts that were subjected to quantitative RT-PCR, further supported the library data. In situ hybridization analyses elucidated specific and enhanced expressions of von Willebrand factor-like transcript during S. pistillata allogeneic rejection. Availability of such genome-wide expression tools may lead to significant advances in the research of coral historecognition and comparative immunology.