Anticipatory gene regulation driven by maternal effects in an insect-host system.

Adaptive mechanisms involved in the prediction of future environments are common in organisms experiencing temporally variable environments. One of these is AGR (anticipatory gene regulation); in which differential gene expression occur in an individual, triggered by the experience of an ancestor. In this study, we explored the existence of AGR driven by a maternal effect, in an insect-host system. We analyzed gene expression of detoxifying systems in aphids across two generations, by shifting mothers and offspring from chemically defended to nondefended hosts, and vice versa. Then, we measured fitness (intrinsic rate of increase) and the relative abundance of transcripts from certain candidate genes in daughters, using RT-qPCR (quantitative reverse-transcription PCR). We found AGR in most cases, but responses varied according to the system being analyzed. For some pathways (e.g., cathepsins), the experience of both mothers and offsprings affected the response (i.e., when both, mother and daughter grew in the defended host, the maximum response was elicited; when only the mother grew in the defended host, an intermediate response was elicited; and when both, mother and daughter grew in a nondefended host, the response was undetectable). In other cases (esterases and GSTs), gene over-expression was maintained even if the daughter was transferred to the nondefended host. In spite of these changes at the gene-regulatory level, fitness was constant across hosts, suggesting that insects keep adapted thanks to this fluctuating gene expression. Also, it seems that that telescopic reproduction permits aphids to anticipate stressful environments, by minute changes in the timing of differential gene expression.