Rapidly evolving lamins in a chordate, Oikopleura dioica, with unusual nuclear architecture.

Metazoan lamins are implicated in the organization of numerous critical nuclear processes. Among chordates, the appendicularian, Oikopleura dioica, has an unusually short life cycle involving rapid growth through extensive recourse to endoreduplication, a characteristic more associated with some invertebrates. In some tissues, this is accompanied by the formation of elaborate, bilaterally symmetric nuclear morphologies associated with specific gene expression patterns.

The Oikopleura coenocyst, a unique chordate germ cell permitting rapid, extensive modulation of oocyte production.

The ability to adjust reproductive output to environmental conditions is important to the fitness of a species. The semelparous, chordate, Oikopleura dioica, is particularly adept in producing a highly variable number of oocytes in its short life cycle. Here we show that this entails an original reproductive strategy in which the entire female germline is contained in a single multinucleate cell, the "coenocyst".

The cytoskeleton organizes germ nuclei with divergent fates and asynchronous cycles in a common cytoplasm during oogenesis in the chordate Oikopleura.

Germline cysts are conserved structures in which cells initiating meiosis are interconnected by ring canals. In many species, the cyst phase is of limited duration, but the chordate, Oikopleura, maintains it throughout prophase I as a unique cell, the coenocyst. We show that despite sharing one common cytoplasm with meiotic and nurse nuclei evenly distributed in a 1:1 ratio, both entry into meiosis and subsequent endocycles of nurse nuclei were asynchronous.

Spliced-leader RNA trans splicing in a chordate, Oikopleura dioica, with a compact genome.

trans splicing of a spliced-leader RNA (SL RNA) to the 5' ends of mRNAs has been shown to have a limited and sporadic distribution among eukaryotes. Within metazoans, only nematodes are known to process polycistronic pre-mRNAs, produced from operon units of transcription, into mature monocistronic mRNAs via an SL RNA trans-splicing mechanism. Here we demonstrate that a chordate with a highly compact genome, Oikopleura dioica, now joins Caenorhabditis elegans in coupling trans splicing with processing of polycistronic transcipts.

Diverse genes expressed in distinct regions of the trunk epithelium define a monolayer cellular template for construction of the oikopleurid house.

The filter-feeding house secreted by urochordate Appendicularians is among the most complex extracellular structures constructed by any organism. This structure allows the Appendicularia to exploit a wide range of food particle sizes, including nanoplankton and submicrometer colloids, establishing them as an important and abundant component of marine zooplankton communities throughout the world. The oikoplastic epithelium, a monolayer of cells covering the trunk of the animal, is responsible for secretion of the house.