Is there an association between elongation factor 1-α overdominance in the seastar Pisaster ochraceus and “seastar wasting disease”?

Abstract

View the peer-reviewed version (peerj.com/articles/1876), which is the preferred citable publication unless you specifically need to cite this preprint.Wares JP, Schiebelhut LM. 2016. What doesn't kill them makes them stronger:an association between elongation factor 1-α overdominance in the sea star Pisaster ochraceus and "sea star wasting disease". PeerJ 4:e1876 https://doi.org/10.7717/peerj.1876What doesn't kill them makes them stronger: An association between elongation factor 1-α overdominance in the sea star Pisaster ochraceus and "sea star wasting disease"In recent years, a massive plague has killed millions of sea stars, of many different species, along the Pacific coast of North America. This disease, known as 'sea star wasting disease' (SSWD), is thought to be caused by viral infection. In the affected sea star Pisaster ochraceus, previous work had identified that the elongation factor 1-α (EF1A) locus harbored an intronic insertion allele that is lethal when homozygous yet appears to be maintained at moderate frequency in populations through increased fitness for heterozygotes. The environmental conditions supporting this increased fitness are unknown, but overdominance is often associated with disease. Here, we evaluate populations of P. ochraceus to identify the relationship between SSWD and EF1A genotype.Our data suggest that there may be significantly decreased infection or mortality rates in individuals that are heterozygous at this locus. These results suggest further studies to understand the functional relationship between diversity at EF1A and survival in P. 10 In recent years, a massive plague has killed millions of sea stars, of many different species, 11 along the Pacific coast of North America. This disease, known as 'sea star wasting disease' 12 (SSWD), is thought to be caused by viral infection. In the affected sea star Pisaster 13 ochraceus, previous work had identified that the elongation factor 1-α locus harbored an 14 intronic insertion allele that is lethal when homozygous yet appears to be maintained at 15 moderate frequency in populations through increased fitness for heterozygotes. The 16 environmental conditions supporting this increased fitness are unknown, but 17 overdominance is often associated with disease. Here, we evaluate populations of P. 18 ochraceus to identify the relationship between SSWD and EF1A genotype. Our data suggest 19 that there may be significantly decreased infection or mortality rates in individuals that are 20 heterozygous at this locus. These results suggest further studies to understand the 21 functional relationship between diversity at EF1A and survival in P. ochraceus.

Sea Star Wasting Disease in the Keystone Predator Pisaster ochraceus in Oregon: Insights into Differential Population Impacts, Recovery, Predation Rate, and Temperature Effects from Long-Term Research

“…We believe that, combined with research reported in other publications ([ 1 – 3 , 11 ], the study of SSWD exemplifies the approach advocated by Burge et al [ 12 ]: a “union of the modern and the classic” approaches to understanding marine diseases. For several reasons, the impact of disease on populations and communities is difficult to investigate [ 3 ].…”

“…Counterintuitively, during much of 2014 summer, susceptibility was lower in juveniles compared to adults ( Fig 3 , adults = 55.3 ± 2.6% vs. juveniles 3.9 ± 0.9%). The mechanistic basis for this apparent resistance is unclear and under investigation [ 1 , 11 ]. Possibilities could include: (1) higher frequencies of resistant genotypes or phenotypes among juveniles and recruits, (2) physiological differences between adults and small sea stars that make adults more susceptible to SSWD, (3) higher surface areas and larger volumes of water within the water vascular system in adults to “intercept” or retain water-borne pathogens, respectively, and (4) small size may make recruits harder to detect because they may die “faster.”…”