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The scrambled actin I gene in Uroleptus pisces

Andrew B Dalby1, David M Prescott

  • 1University of Colorado, Department of Molecular Cellular and Developmental Biology, Boulder, CO 80309-0347, USA.

Chromosoma
|January 22, 2004
PubMed

Insights

The actin I gene in Uroleptus pisces is scrambled in two segments, with unique patterns suggesting independent evolution of gene scrambling in stichotrichs. DNA or RNA templates may guide correct splicing.

Area of Science:

  • Molecular Biology
  • Genetics
  • Evolutionary Biology

Background:

  • The micronuclear actin I gene in Uroleptus pisces is organized into two distinct segments.
  • These segments contain macronuclear destined subsegments (MDSs) separated by internal eliminated segments (IESs).
  • The arrangement of MDSs within these segments is highly scrambled and unique to U. pisces.

Purpose of the Study:

  • To analyze the gene structure and organization of the actin I gene in Uroleptus pisces.
  • To compare the gene scrambling pattern with other stichotrich species.
  • To investigate the evolutionary history of gene scrambling in the actin I gene.

Main Methods:

  • Polymerase chain reaction (PCR) was used to attempt to link the two gene segments.
  • Sequence analysis was performed to determine the order and orientation of MDSs and IESs.
  • Comparative analysis of gene structure was conducted with other stichotrich species.

Main Results:

  • The actin I gene in U. pisces consists of two segments with scrambled MDSs and IESs in unique orders.
  • Attempts to connect the two segments via PCR were unsuccessful, suggesting a large IES or separate loci.
  • The scrambling pattern differs significantly from that observed in six other stichotrich species.

Conclusions:

  • Gene scrambling of the actin I gene occurred independently in the lineage leading to U. pisces and in other stichotrichs.
  • Repeated sequences (pointers) at MDS ends are crucial for correct splicing, but non-pointer matches pose challenges.
  • A DNA or RNA template from the previous macronucleus may be required to ensure accurate splicing of the scrambled gene.

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