Differential effect of allorecognition loci on phenotype in Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa) - PubMed (original) (raw)

Differential effect of allorecognition loci on phenotype in Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa)

Anahid E Powell et al. Genetics. 2007 Dec.

Abstract

The allorecognition complex of Hydractinia symbiolongicarpus is a chromosomal interval containing two loci, alr1 and alr2, that controls fusion between genetically distinct colonies. Recombination between these two loci has been associated with a heterogeneous class of phenotypes called transitory fusion. A large-scale backcross was performed to generate a population of colonies (N = 106) with recombination breakpoints within the allorecognition complex. Two distinct forms of transitory fusion were correlated with reciprocal recombination products, suggesting that alr1 and alr2 contributed differentially to the allorecognition response. Specifically, type I transitory fusion is associated with rapid and persistent separation of allogeneic tissues, whereas type II transitory fusion generates a patchwork of continuously fusing and separating tissues.

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Figures

F<sc>igure</sc> 1.—

Figure 1.—

Schematic showing the morphology of a Hydractinia colony. P, polyp; M, mat; S, stolon.

F<sc>igure</sc> 2.—

Figure 2.—

Pedigree used to generate mapping population. 431-63 is a heterozygote, and 833-8 is a homozygote. Squares represent males, and circles represent females. The lineage of 833-8 can be found in Figure 2 of C

adavid

et al. (2004) and likewise the heterozygous male (431-63) was a member of the 431 population represented as the final product of the mating program in C

adavid

et al. (2004).

F<sc>igure</sc> 3.—

Figure 3.—

Initial stages of fusion and transitory fusion. (A) Colony assay prior to contact where the two colonies grow side by side. (B) Fusion 48 hr later showing continuity between mat tissue and gastrovascular canals. Bar, 200 μm.

F<sc>igure</sc> 4.—

Figure 4.—

Outcome of type I transitory fusion. This close-up of interacting tissue between colonies depicts the outcome of type I transitory fusion. The two colonies have already undergone fusion and initial stages of rejection and have separated, indicated by the white fibrous material between the colonies that creates a border (arrow). Note also the gastrovascular canals that branch laterally along the line of separation and rejoin one another. P, polyps. Bar, 200 μm.

F<sc>igure</sc> 5.—

Figure 5.—

Two stages of type II transitory fusion. This region of interacting tissue between two colonies depicts the separation and refusion phases that occur in type II transitory fusion. (A) The separation phase after the colony has already undergone contact and fusion. The zone of interaction/separation is indicated by an arrow. This is an early stage of separation common to both type I and II transitory fusion where the mat and gastrovascular canals are separate, but unlike Figure 4, there is no border accumulation or extensive lateral branching of canals. (B) Refusion 24 hr later. The arrow indicates one of several areas where colonies have rejoined their gastrovascular canals. P, polyps. Bar, 200 μm.

F<sc>igure</sc> 6.—

Figure 6.—

Genetic map of the allorecognition complex. Markers are named as in Table 1. Loci are alr1 and alr2. Bar, 0.1 cM as shown. The total mapped interval represents 1.7 cM. Numbers below the map represent how many recombinants were recovered between each of the markers.

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