Pierre Léopold

Amino acid storage proteins, such as serum albumin in mammals, are known to accumulate within tumors, but their precise contribution to tumor biology remains unclear. Using both cachectic and noncachectic tumor models in Drosophila , we observed that fat body–derived hexamerins accumulate in the tumors through a selective uptake process. Disabling this uptake led to a marked reduction in tumor growth, demonstrating that hexamerins are used as a nutrient source to support cancer progression. Hexamerin uptake also supports expression of the relaxin-like Drosophila insulin-like protein 8 (Dilp8) by the tumor, inhibiting ecdysone production and extending the growth period. This coupling between nutrient uptake by the tumor and inhibition of the developmental progression exerts a full diversion of the host resources. Functional parallels with mammalian albumins suggest evolutionarily conserved mechanisms with potential implications for cancer biology.

Amino acid storage proteins, such as serum albumin in mammals, are known to accumulate within tumors, but their precise contribution to tumor biology remains unclear. Using both cachectic and non-cachectic tumor models in Drosophila , we observed that fat body-derived hexamerins accumulate in the tumors through a selective uptake process. Disabling this uptake led to a marked reduction in tumor growth, demonstrating that hexamerins are used as a nutrient source to support cancer progression. Hexamerin uptake also supports expression of the relaxin-like Dilp8 by the tumor, inhibiting ecdysone production and extending the growth period. This coupling between nutrient uptake by the tumor and inhibition of the developmental progression exerts a full diversion of the host resources. Functional parallels with mammalian albumins suggest evolutionarily conserved mechanisms with potential implications for cancer biology.

Understanding how final organ size is established during development raises two key questions: how organs increase their mass and how they stop growing upon reaching an appropriate size. While organ growth is driven by conserved signaling pathways, the mechanisms underlying growth arrest remain elusive. Studies on Drosophila imaginal wing discs have provided a model whereby final organ size coincides with an arrest of cell proliferation at the end of the larval phase. Here, through 3D reconstruction and volume measurements, we show that wing discs grow continuously throughout the larva-to-pupa (L/P) transition and proceed to growth arrest later during the pupal period. This supplemental growth phase involves a switch at the L/P transition that uncouples proliferation from tissue growth, with an important contribution from Insulin/IGF signaling. These findings challenge the existing model of imaginal wing development and open new avenues for our understanding of growth arrest and organ size determination.

SUMMARY: Organisms have evolved strategies to store resources and overcome periods of low or no nutrient access including transient shortages or longer non-feeding developmental transitions. Holometabolous insects like Drosophila represent an attractive model to study resource allocation during development since they alternate feeding and non-feeding periods. Amino acids are essential components for tissue growth and renewal, but the strategies used for their storage remain largely unexplored. Here, we uncover a 2-step mechanism for the temporal production, storage and use of specific storage proteins called hexamerins. Moreover, we show that modulating amino acid storage affects the relative growth of organs across developmental phases and, as a consequence, alters body allometry and adult fitness.

The postulates of developmental instability–sexual selection hypothesis is intensely debated among evolutionary biologists, wherein despite a large amount of empirical data, evidence for or against it has been largely inconclusive. A key assumption of this hypothesis is that animals assess symmetry in potential mates as an indicator of genetic quality (developmental stability), and consequently use this information to discriminate against those with higher asymmetries while choosing mates. However, the perceptional basis that must underlie such discriminatory behavior (is symmetry a signal or is symmetry signaled) is not clearly defined. It is also argued that since asymmetry levels in natural populations are very low, the low signal‐to‐noise ratio would make accurate assessment of symmetry both difficult and costly. Rather than attempting to validate this hypothesis or even as to whether animals assess mate symmetry, this review simply aims to examine the plausibility that animals perceive symmetry (directly or indirectly) and consequently discriminate against asymmetric mates in response to perceived irregularities during courtship. For this, we review mate choice and courtship literature to identify potential sensory cues that might advertise asymmetry or lead to discrimination of asymmetric individuals. Although signaling associated with mate choice is commonly multimodal, previous studies on asymmetry have mainly focused on visual perception. In the light of a recent study (Vijendravarma et al., 2022,Proceedings of the National Academy of Sciences of the United States of America, 119, e2116136119), this review attempts to balance this bias by emphasizing on non‐visual perception of asymmetry. In conclusion, we discuss the methodological challenges associated with testing the role of multimodal cues in detecting mate asymmetry, and highlight the importance of considering ecological, behavioral, and evolutionary aspects of animals while interpreting empirical data that test such hypothesis.

Significance: Theoretically, symmetry in bilateral animals is subject to sexual selection, since it can serve as a proxy for genetic quality of competing mates during mate choice. Here, we report female preference for symmetric males inDrosophila, using a mate-choice paradigm where males with environmentally or genetically induced wing asymmetry were competed. Analysis of courtship songs revealed that males with asymmetric wings produced songs with asymmetric features that served as acoustic cues, facilitating this female preference. Females experimentally evolved in the absence of mate choice lost this preference for symmetry, suggesting that it is maintained by sexual selection.