A subtle defect underlies altered lamellar orientation in the Gr super(16) chorion mutant of Bombyx mori

• Published in: Developmental biology Vol. 157; no. 1; pp. 60 - 72
• Main Authors: Gautreau, D, Zetlan, SR, Mazur, C D, Goldsmith, M R
• Format: Journal Article
• Language: English
• Published: 01-01-1993
• Subjects: Bombyx mori
• ISSN: 0012-1606

Gr super(16) (chromosome 2, 6.9 cM) is a dominant, grey egg mutation of the domestic silkmoth, Bombyx mori , which produces an opaque instead of a translucent chorion. To determine the underlying cause of this defect, we examined the effects of the mutation of chorion ultrastructure, protein accumulation, and biosynthesis patterns, and on the restriction patterns of early chorion structural genes, using the presumed wild-type progenitor strain, Old European 16 (OE16), for comparison. Mature chorion protein patterns resolved by isoelectric focusing or two-dimensional polyacrylamide gel electrophoresis, synthetic profiles of virtually all chorion proteins following pulse-labeling with tritiated or ( super(14)C)glycine, and restriction patterns of early chorion genes examined by Southern blot hybridization were identical between mutant, wild-type, and heterozygote. These observations ruled out a major deletion of chorion structural genes or defects in the production and accumulation of normal chorion proteins as mechanisms underlying the mutation, unlike other putative Gr mutants mapping in its vicinity. Based on these observations, we postulate that the Gr super(16) mutation affects the primary structure of a minor, previously unidentified chorion or follicular cell component which is critical for determining lamellar orientation, and discuss models of how this might function.