Meeting Abstract

55-4  Sunday, Jan. 5 11:15 – 11:30  Body size sensing in the tobacco hornworm, Manduca sexta: the role of TGF-beta/Activin signaling in metamorphic timing HE, L; SHIN, SHJ; WANG, Z; YUAN, I; WESCHLER, R; KOYAMA, T; NIJHOUT, HF; SUZUKI, Y*; Wellesley College, Wellesley, MA; Wellesley College, Wellesley, MA; Wellesley College, Wellesley, MA; Wellesley College, Wellesley, MA; Wellesley College, Wellesley, MA; University of Copenhagen, Copenhagen, Denmark; Duke University, Durham, NC; Wellesley College, Wellesley, MA ysuzuki@wellesley.edu

How organisms sense their size remains poorly understood. In insects, the final larval instar is specified if they have attained the threshold size; if they have not, they will undergo additional larval molts and continue to grow. In this study, the nature of threshold size determination was investigated using the tobacco hornworm, Manduca sexta. Hypoxia treatment caused larvae to have a lower threshold size than those reared on low nutrient diet. Measurements of relative sizes of muscles and fat body showed that the size of the muscles/integuments was correlated with the attainment of threshold size. In addition, we found that the expression of the TGF-beta/Activin signaling gene, myoglianin (myo), was associated with the attainment of threshold size and that its knockdown led to supernumerary molts and prevented metamorphosis. We will present a model for how larvae sense their size.