Evolution

Parallel evolution of the genetic code in arthropod mitochondrial genomes. Abascal, F. et al. PLoS Biol. 4, e127 (2006)

To investigate the extent to which the genetic code varies, the authors compared the codon usage of mitochondria in 626 animal species using automated computational methods. Arthropods stood out as they have evolved non-standard codons: AGG is translated as either Lys or Ser (instead of Ser only). The frequent reoccurrence of this codon reassignment, as well as the pattern of genetic change, indicates that codons are reassigned more easily than was previously believed, and suggests that codon usage in other lineages might be similarly labile.

Transcription

The role of Rat1 in coupling mRNA 3′-end processing to transcription termination: implications for a unified allosteric-torpedo model. Luo, W. et al. Genes Dev. 20, 954–965 (2006)

Two models have been proposed for how RNA polymerase II terminates transcription. The allosteric model posits that the polymerase falls off the template owing to conformational changes that are triggered by the poly(A) sequence. According to the 'torpedo' model exonucleases digest the growing RNA strand until they hit the elongation complex. This paper shows that an integrated model is more plausible: the enzymatic function of the Rat1 and Xrn1 exonucleases is not sufficient to displace the polymerase, which requires additional factors, including an allosteric effector, that are recruited by Rat1.

Synthetic biology

Emergent properties of reduced-genome Escherichia coli. Pósfai, G. et al. Science 27 April 2006 (doi:10.1126/science.1126439)

The authors used a recombination-based approach to delete up to 15% of the Escherichia coli K-12 genome. Removal of mainly large islands, insertion-sequence-containing islands and individual genes containing insertion-sequence elements led to some unexpected properties. Without compromising growth dynamics, the authors created a strain that showed increased electroporation efficiency and enhanced propagation and stability of plasmids, which are used as delivery vehicles in vaccine and gene therapy research.

Parasite genetics

Natural malaria infection in Anopheles gambiae is regulated by a single genomic control region. Riehle, M. M. & Markianos, K. et al. Science 312, 577–579, (2006)

A survey of genetic variation in a West African population of the mosquito Anopheles gambiae has identified a cluster of strong resistance loci on chromosome 2L, which forms a Plasmodium-resistance island. Among the candidate genes within this 15-Mb region, the authors identified Anopheles Plasmodium-responsive leucine-rich repeat 1 (APL1), the homologues of which are involved in natural resistance mechanisms in plants and mammals. The role of APL1 in Plasmodium resistance was confirmed by RNAi.