C-Terminal Moiety of Tudor Contains Its In Vivo Activity in Drosophila

Joël Anne,Patrick Callaerts

doi:10.1371/journal.pone.0014378

Abstract

BackgroundIn early Drosophila embryos, the germ plasm is localized to the posterior pole region and is partitioned into the germline progenitors, known as pole cells. Germ plasm, or pole plasm, contains the polar granules which form during oogenesis and are required for germline development. Components of these granules are also present in the perinuclear region of the nurse cells, the nuage. One such component is Tudor (Tud) which is a large protein containing multiple Tudor domains. It was previously reported that specific Tudor domains are required for germ cell formation and Tud localization.Methodology/Principal FindingsIn order to better understand the function of Tud the distribution and functional activity of fragments of Tud were analyzed. These fragments were fused to GFP and the fusion proteins were synthesized during oogenesis. Non-overlapping fragments of Tud were found to be able to localize to both the nuage and pole plasm. By introducing these fragments into a tud mutant background and testing their ability to rescue the tud phenotype, I determined that the C-terminal moiety contains the functional activity of Tud. Dividing this fragment into two parts reduces its localization in pole plasm and abolishes its activity.Conclusions/SignificanceI conclude that the C-terminal moiety of Tud contains all the information necessary for its localization in the nuage and pole plasm and its pole cell-forming activity. The present results challenge published data and may help refining the functional features of Tud.

Highlights

In a wide variety of animals, germ cells are formed in a specialized region of the egg cytoplasm, called the germ plasm, which contains characteristic electron-dense organelles, the germinal granules [1,2]
By comparison to the other nuage and polar granule components Tud displays specific characteristics: it is not required for the repression of heterochromatin retrotransposons [13] and Tud is bound to the fibrous material connecting polar granules and mitochondria [14]
Tud is involved in the transport of mitochondrial ribosomal RNAs from mitochondria to polar granules [14] and the assembly of mitochondrial-type ribosomes in these structures, which is necessary for pole cell formation [15]

Summary

Introduction

In a wide variety of animals, germ cells are formed in a specialized region of the egg cytoplasm, called the germ plasm, which contains characteristic electron-dense organelles, the germinal granules [1,2]. In Drosophila, assembly of the germinal granules, or polar granules [3], requires the function of maternaleffect genes Among these genes are oskar, vasa (vas), tudor (tud), and valois (vls) which are essential for the formation of pole cells, the germline progenitors [4]. These genes produce proteins that localize to the polar granules [5,6,7,8,9]. Pole plasm, contains the polar granules which form during oogenesis and are required for germline development Components of these granules are present in the perinuclear region of the nurse cells, the nuage. It was previously reported that specific Tudor domains are required for germ cell formation and Tud localization

Methods

Results

Conclusion