Worm Breeder's Gazette 11(1): 45

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Evolution of the MSP Multigene family in the Nematode Caenorhabditis elegans

David Ammons, Samuel Ward, Michael Klass and George Fox

Figure 1

We have determined the nucleotide sequence of 37 major sperm protein 
(MSP) genes in C.  elegans.  The sequence data has been used to 
construct an evolutionary tree using the unweighted pair-group method 
with arithmetic mean (UPGMA), Figure 1.  The most obvious result is 
the strong correlation between genomic location and sequence 
similarity.  Each phylogenetic cluster of genes corresponds to one of 
four genomic gene clusters (msp-72ps is isolated by itself on 
chromosome V).  Surprisingly, when the sequence data was restricted to 
different regions within the MSP genes, phylogenetic relationships 
varied considerably.  The variability however was only observed among 
the genes within each cluster, the overall phylogeny of the four 
clusters was left unchanged.  This result suggests that phylogenetic 
information varies along many of the gene sequences but in a manner 
that would retain the partitioning of the clusters.  More detailed 
analysis of the data confirmed this and demonstrated that many genes 
are in fact historically mosaic, comprised of DNA sequences similar to 
other genes within the same cluster.  In many cases the basis for an 
individual gene's mosaic nature is best explained by the high number 
of apparent genetic recombination/gene conversion events observed.  
These events appear to be more prevalent, and probably greatly 
restricted, to genes found in close proximity to one another within 
the clusters.  For example, genes from cluster II-L that demonstrate 
genetic exchange, or 100% homology among themselves, can be placed 
into four groups.  These four groups correlate very well with proposed 
sub-clusters inferred from the relative genomic locations of the genes.
In the other clusters the mosaic nature of the genes is also evident,
yet possibly do to age, the mosaicism is characterized by shorter 
less obvious stretches of sequence similarity.  Figure 1 would also 
suggest that the IV-L cluster of genes is relatively recent and 
originated from the II-L gene cluster.  The high conservation of 5' 
flanking regions also supports this conclusion.
[See Figure 1]

Figure 1