Hsp60C is required in follicle as well as germline cells during oogenesis in Drosophila melanogaster

Abstract

Hsp60C gene of Drosophila melanogaster shows a dynamic spatiotemporal expression during oogenesis and seems to contribute bulk of the Hsp60 family proteins in ovarioles. Hsp60 distribution overlaps with that of F-actin-rich membranes/structures in follicle, nurse, and egg cells throughout oogenesis. Skeletal muscle fibers associated with ovarioles and in other parts of the body show patterned location of Hsp60 in A-bands. During stages 11-12, Hsp60 accumulates at junctions of nurse cells and oocyte, where a new microtubule organizing center is known to develop. A recessive hypomorph allele, Hsp60C₁ causes complete sterility of the rare surviving homozygous adults. Their egg chambers show very little Hsp60C transcripts or Hsp60 protein. Beginning at stages 6-7, Hsp60C₁ chambers show a disorganized follicle cell layer with poor cell adhesion in addition to abnormal organization of F-actin and other cytoskeletal structures in follicle, nurse, and egg cells. Additionally, expression and localizations of Hrb98DE, Squid, and Gurken proteins in nurse cells and oocyte are also severely affected. Hsp60C₁ homozygous follicle cell clones in Hsp60C₁/+ ovarioles show disruptions in follicle epithelial and cytoskeleton arrangements. Likewise, egg chambers with Hsp60C₁ homozygous germline clones in Hsp60C₁/+ flies show abnormal oogenesis. Our results provide the first evidence for an essential role of Hsp60C in Drosophila oogenesis, especially in organization and maintenance of cytoskeletal and cell adhesion components.