Abstract
In developmental biology, the sequence of gene induction and pattern formation is best studied over time as an organism develops. However, in the model system of Drosophila larvae this oftentimes proves difficult due to limitations in imaging capabilities. Using the larval wing imaginal disc, we show that both overall growth, as well as the creation of patterns such as the distinction between the anterior(A) and posterior(P) compartments and the dorsal(D) and ventral(V) compartments can be studied directly by imaging the wing disc as it develops inside a larva. Imaged larvae develop normally, as can be seen by the overall growth curve of the wing disc. Yet, the fact that we can follow the development of individual discs through time provides the opportunity to simultaneously assess individual variability. We for instance find that growth rates can vary greatly over time. In addition, we observe that mechanical forces act on the wing disc within the larva at times when there is an increase in growth rates. Moreover, we observe that A/P boundary formation follows the established sequence and a smooth boundary is present from the first larval instar on. The division of the wing disc into a dorsal and a ventral compartment, on the other hand, develops quite differently. Contrary to expectation, the specification of the dorsal compartment starts with only one or two cells in the second larval instar and a smooth boundary is not formed until the third larval instar.
Highlights
In the recent past, the focus of many biological investigations has shifted from a single gene perspective to one concerned with a mathematical modeling of the process in question [1]
Mechanical feedback models have been proposed for the explanation of uniform growth and growth termination [6,7,8], which predict a temporal development of growth and the buildup of mechanical forces
Growth Properties of the Wing Imaginal Disc To assess whether larvae developed normally, we studied the area of the wing disc over time
Summary
The focus of many biological investigations has shifted from a single gene perspective to one concerned with a mathematical modeling of the process in question [1]. To accurately model a developmental process by predicting the sequence of events, temporal information on gene induction and patterning, as well as growth, is requisite. For instance, models have implicated the influence of temporally varying growth factor expression as a way of explaining uniform growth and termination of growth [5] This needs to be tested on time dependent data of the expression of said growth factors. Mechanical feedback models have been proposed for the explanation of uniform growth and growth termination [6,7,8], which predict a temporal development of growth and the buildup of mechanical forces These models need to be tested against time dependencies from the biological system. Quantitative models on growth control predict time sequences which need to be studied experimentally
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