Bindin from a sea star

Abstract

The genetic basis for the evolution of development includes genes that encode proteins expressed on the surfaces of sperm and eggs. Previous studies of the sperm acrosomal protein bindin have helped to characterize the adaptive evolution of gamete compatibility and speciation in sea urchins. The absence of evidence for bindin expression in taxa other than the Echinoidea has limited such studies to sea urchins, and led to the suggestion that bindin might be a sea urchin-specific molecule. Here we characterize the gene that encodes bindin in a broadcast-spawning asterinid sea star (Patiria miniata). We describe the sequence and domain structure of a full-length bindin cDNA and its single intron. In comparison with sea urchins, P. miniata bindin is larger but the two molecules share several general features of their domain structure and some sequence features of two domains. Our results extend the known evolutionary history of bindin from the Mesozoic (among the crown group sea urchins) into the early Paleozoic (and the common ancestor of eleutherozoans), and present new opportunities for understanding the role of bindin molecular evolution in sexual selection, life history evolution, and speciation among sea stars.

Fig. 1

Inferred amino acid sequence for the complete Patiria miniata bindin cDNA. Domains are distinguished by type face: signal sequence (gray), collagenlike (green), A (cyan), B (red), C (blue), core (bold). Preprobindin sequence (ending in the probable cleavage motif RARR) is underlined. Highly conserved cysteine residues in preprobindin are shown in bold italics. Repeats are numbered above each sequence. Arrows show location and direction of PCR primers (Table 1) used in RACE experiments or in amplification from cDNA or genomic DNA. Large arrowhead shows the location of a single 1005 bp intron in codon 959 (leucine). Boxes show peptide fractions identified in sperm by tandem mass spectrometry.

Fig. 2

Hydrophobicity of Patiria miniata bindin using the Kyte and Doolittle (1982) method.