GUNTER, H M; DEGNAN, B M*; Univ. of Queensland, Australia; Univ. of Queensland, Australia: Developmental and heat shock response roles of Hsp90 in Haliotis asinina larvae.

Heat shock protein 90 is a chaperone, a developmental regulator and stress protein. Stress diverts Hsp90 from its developmental role and its occurrence during development can unlock cryptic genetic variation (Queitsch and Lindquist 2002). Here we examine the role of Hsp90 in development and its redeployment during stress in the tropical abalone, Haliotis asinina, reared at normal and elevated temperatures (29°C, 30°C and 31°C; control=25°C) through spatial expression analysis including situ hybridisation and immunocytochemistry. At normal temperatures, maternal transcripts are restricted to the animal pole of the egg and are detected in the micromere lineage and the animal half of the macromeres during early cleavage. Hsp90 then is upregulated in the developing prototroch, a subset of cells in the pretrochal ectoderm and the ventrolateral ectoderm that later develops into the foot and mantle. In mature veligers, Hsp90 mRNA is upregulated in the pallial cavity, the developing nervous system and buccal cavity. In situ hybridisation of heat shocked embryos did not reveal a significant shift in the spatial expression pattern of Hsp90. While increased temperatures induced a broad range of abnormal phenotypes, particularly at 30°C and 31°C, individuals with a recognisable trochophore body plan displayed the characteristic staining pattern. Therefore, Hsp90 maintains its developmental expression pattern during heat shock, in spite of its additional stress related role. This suggests that maintenance of Hsp90 in a spatially restricted pattern during heat shock is important in the progression of development. Queitsch, C. and S. Lindquist (2002). “Hsp90 as a capacitor of phenotypic variation.” Nature 749: 1-7.