Ars Technica reports on a Nature study from a RIKEN-led team showing that fruit flies retain a nutritional memory of their larval diet. When larvae were fed a low-protein, low-yeast diet, the adult flies lived longer than siblings fed standard food — even though both groups ate the same diet after emerging. The effect came with trade-offs: adults were paler and lighter, sometimes by 28 percent, and females laid fewer eggs.
Using stable isotope tagging, the researchers traced amino acids eaten by larvae into adult fly heads. Three days into adulthood, nearly 64 percent of head proteins were still built from larval amino acids; by day six, about 46 percent were. A storage protein called Lsp2 stood out. Larvae on low protein made less Lsp2, and that low level persisted, leading to fewer ribosomes and slower protein production in young adults. Genetically silencing Lsp2 produced the same longer-lived phenotype.
Obata's team also found that Lsp2 is rich in phenylalanine and tyrosine; restricting either amino acid in larval food lowered Lsp2 and extended lifespan, while restricting isoleucine did nothing. The researchers regard the final step — less protein production improving proteostasis and extending lifespan — as the most firmly established. Why Lsp2 links to ribosomes is less clear, and the paper leaves that mechanism as an open question.