How organs coordinate their development with body decoded

The development of wings in fruit flies does not progress synchronously with the organism's development, a new study has found.
A research group led by Christen Mirth at Instituto Gulbenkian de Ciencia, Portugal, found that development of wings in fruit flies is coordinated with the whole body only at distinct 'milestones'.
The study helps explain how an organism facing environmental and physiological perturbations retains the ability to build correct functional organs and tissues in a proportional adult body.
For a growing organism it is essential to have robust developmental processes ensuring that the developing organs and tissues are formed correctly even in the face of environmental or physiological perturbations.

To achieve robustness, the processes that generate individual organs must, at some level, be integrated across the whole body to ensure that a correctly patterned and proportioned adult is produced at the end of development.
Mirth and colleagues proposed to study how organ and whole-body development is coordinated, using the fruit fly, Drosophila melanogaster, as a model organism.

The juvenile period in the fruit fly comprises three larval moults, followed by a wandering stage where larvae leave the food and search for a site to begin metamorphosis at a stage called pupariation.
The research team focused on these so-called developmental events to study how the development of wings is coordinated with the whole body of the fruit fly larvae.

The researchers first analysed the expression of six genes involved in the development of wings in normal conditions of growth, at a temperature of 25 degrees Celsius, and generated a detailed staging scheme.
Next, the researchers changed the temperature to affect the growth conditions of the larvae and analysed the rate of wing development compared to the whole-body development.
It is known that flies grow faster at higher temperatures and grow slower at lower temperatures.
However, the researchers observed that the development of the wings was slower at 29 degrees Celsius, compared to flies growing in normal conditions or flies growing at 18 degrees Celsius.

"This result surprised us, as we could clearly observe a delay in the development of these wings in wandering stage larvae, but their progression accelerated towards the stage of pupariation," said Marisa Oliveira, first author of the study published in the journal PLOS Genetics.
"This means that development shows variability in its progression, but converges at the milestone of pupariation," Oliveira added.