Evolution of PEX genes

A nice evolutionary analysis of peroxin genes entitled PEX Genes in Fungal Genomes: Common, Rare, or Redundant in the journal “Traffic” from Kiel et al out of the University of Groningen in The Netherlands. Within a species, the genes in the PEX family are not necessarily phylogenetically related to each other, but instead are all named as to how they were discovered in mutant screens, most of which were done in S. cerevisiae.

Peroxisomes are interesting because they are necessary for some biochemical reactions (fatty acid metabolism). In filamentous fungi there are additionally specialized peroxisomes called Woronin bodies that plug the septal pore that separates individuals cells in a hyphae. These are specific to filamentous fungi so it is interesting to contrast the numbers and types of genes in the PEX family that are present as determined from the genome sequences. To relate this to human biology, the authors suggest that understanding the complex phenotypes of human peroxisome biogenesis disorders (PBD) will be helped through the study of the disruptions of PEX genes in various filamentous fungi. Interestingly, they find that nearly all PEX genes are present in all fungi, yeast and filamentous alike, although there may be additional genes unidentified.

Woronin bodies
Woronin bodies in A. nidulans from Momany et al, Mycologia 2002

There is still more work that can be done here. From what I can tell, they only used a BLAST-based approach to identify genes and look for unannotated PEX genes – a more sophisticated splicing-aware alignment approach like Exonerate or Genewise might help clarify if they are missing any genes. Looking at additional species that are dimorphic with a yeast and filamentous form and whether or not there are PEX genes that are expressed only in yeast or filamentous stage, or look at localization of proteins during yeast phase that are known to be in Woronin bodies. This might might help further dissect if the genes have phase-specific function. Also, a good phylogenetic study that looked at trees of the genes which are duplicated to try and deduce the timing of duplication and whether any of them correlate with timing of morphological changes.

2 thoughts on “Evolution of PEX genes”

  1. I am actually quite interested in getting more into this type of work. Not just at the level of gene content but making the connection between proteins/networks/phenotypes and how they evolve. Thanks for the info.

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