TY - JOUR

T1 - Distinct nutritional and endocrine regulation of prothoracic gland activities underlies divergent life history strategies in Manduca sexta and Drosophila melanogaster

AU - Xu, Lily C.

AU - Nunes, Catarina

AU - Wang, Victoria R.

AU - Saito, Akiho

AU - Chen, Teresa

AU - Basak, Priyanka

AU - Chang, Jane J.

AU - Koyama, Takashi

AU - Suzuki, Yuichiro

PY - 2020

Y1 - 2020

N2 - Life history trade-offs lead to various strategies that maximize fitness, but the developmental mechanisms underlying these alternative strategies continue to be poorly understood. In insects, trade-offs exist between size and developmental time. Recent studies in the fruit fly Drosophila melanogaster have suggested that the steroidogenic prothoracic glands play a key role in determining the timing of metamorphosis. In this study, the nutrient-dependent growth and transcriptional activation of prothoracic glands were studied in D. melanogaster and the tobacco hornworm Manduca sexta. In both species, minimum viable weight (MVW) was associated with activation of ecdysteroid biosynthesis genes and growth of prothoracic gland cells. However, the timing of MVW attainment in M. sexta is delayed by the presence of the sesquiterpenoid hormone, juvenile hormone (JH), whereas in D. melanogaster it is not. Moreover, in D. melanogaster, the transcriptional regulation of ecdysteroidogenesis becomes nutrient-independent at the MVW/critical weight (CW) checkpoint. In contrast, in M. sexta, starvation consistently reduced transcriptional activation of ecdysteroid biosynthesis genes even after CW attainment, indicating that the nature of CW differs fundamentally between the two species. In D. melanogaster, the prothoracic glands dictate the timing of metamorphosis even in the absence of nutritional inputs, whereas in M. sexta, prothoracic gland activity is tightly coupled to the nutritional status of the body, thereby delaying the onset of metamorphosis before CW attainment. We propose that selection for survival under unpredictable nutritional availability leads to the evolution of increased modularity in both morphological and endocrine traits.

AB - Life history trade-offs lead to various strategies that maximize fitness, but the developmental mechanisms underlying these alternative strategies continue to be poorly understood. In insects, trade-offs exist between size and developmental time. Recent studies in the fruit fly Drosophila melanogaster have suggested that the steroidogenic prothoracic glands play a key role in determining the timing of metamorphosis. In this study, the nutrient-dependent growth and transcriptional activation of prothoracic glands were studied in D. melanogaster and the tobacco hornworm Manduca sexta. In both species, minimum viable weight (MVW) was associated with activation of ecdysteroid biosynthesis genes and growth of prothoracic gland cells. However, the timing of MVW attainment in M. sexta is delayed by the presence of the sesquiterpenoid hormone, juvenile hormone (JH), whereas in D. melanogaster it is not. Moreover, in D. melanogaster, the transcriptional regulation of ecdysteroidogenesis becomes nutrient-independent at the MVW/critical weight (CW) checkpoint. In contrast, in M. sexta, starvation consistently reduced transcriptional activation of ecdysteroid biosynthesis genes even after CW attainment, indicating that the nature of CW differs fundamentally between the two species. In D. melanogaster, the prothoracic glands dictate the timing of metamorphosis even in the absence of nutritional inputs, whereas in M. sexta, prothoracic gland activity is tightly coupled to the nutritional status of the body, thereby delaying the onset of metamorphosis before CW attainment. We propose that selection for survival under unpredictable nutritional availability leads to the evolution of increased modularity in both morphological and endocrine traits.

KW - Critical weight (CW)

KW - Ecdysteroid

KW - Halloween genes

KW - Juvenile hormone (JH)

KW - Minimum viable weight (MVW)

KW - Prothoracic gland (PG)

U2 - 10.1016/j.ibmb.2020.103335

DO - 10.1016/j.ibmb.2020.103335

M3 - Journal article

C2 - 32061770

AN - SCOPUS:85079606552

VL - 119

JO - Insect Biochemistry and Molecular Biology

JF - Insect Biochemistry and Molecular Biology

SN - 0965-1748

M1 - 103335

ER -