Overexpression of the isolated protease domain of the Nudel protein does not affect Dorsal-Ventral polarity determination in Drosophila
Abstract
Most of living organisms begin life from one-cell egg. Generally, an egg begins developments
after it gets fertilized. From very early stages, however, depending on the locations in an embryo,
each embryonic cell undergoes specific patterns of differentiation. Therefore, the determination
and recognition of spatial coordination within an embryo are important before any other
developmental events can occur. Due to the lack of zygotic genome, many embryos initially use
maternal materials to generate the axes of head-to-tail (Anterior-Posterior, AP) and back-to-belly
(Dorsal-Ventral, DV). Also, the environmental surroundings, such as the presence of an egg shell
structure, can also influence the axes. In Drosophila, the existence of follicle cells surrounding
the egg during its formation, which provide nutrition and genetic materials to an egg, generates
asymmetrical egg shape. With the ability to distinguish specific region in the egg, researchers
found the localization of maternal genetic materials at particular sites within the egg, and showed
them to be responsible for the determination of the axes. Those maternal genes were identified to
work as switches that will turn on and off zygotic genes we need to be expressed at a specific
region or at the specific timing during development. Although the individual functions of
maternal genes have been studies in artificial conditions, the combinatorial activities of those
materials in living cells are still not fully understood. Mutations affecting the Nudel protein, one
of the maternal gene products involved in development, produce an abnormal dorsal-ventral
polarity in an embryo or an embryo with aberrant eggshell structure, depending on the position
of the mutation within the protein. The unusually large size of protein Nudel is composed of
several parts showing different functions. The increasing amount of one portion of protein Nudel,
which has a function as an enzyme, does not affect the determination of DV axis or development
of eggshell structure. Further research should address the functionality of Nudel protease
whether it requires direct activities of Nudel protein or it has the correct construct to express the
protease.