Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Analysis Of Orthologous Genes In Polyploid Wheat Revealed That The Translated Part Of Genes Is Protected Against Changes By An Unknown Mechanism Independent Of Selection Pressure

Jasdeep S Mutti , Kulvinder S Gill

  277 Johnson Hall, Washington State University, Pullman, WA, 99164 USA

Hexaploid wheat (Triticum aestivum L., AABBDD, 2n=2x=42) is a relatively young polyploid with its evolution from diploid to tetraploid ~ .5 MYA and from tetraploid to hexaploid only ~10,000 years ago. Detailed sequence analysis of orthologs of 43 genes out of the 200 that were studied, showed that on an average there were 40 SNP, 2.3 two bp substitution (BPS) and 1.7 two to five bp deletions (BPD) per kb of the transcribed region. The translated part of the gene contained only 20 SNP, 0.1 BPS and 0.01 BPD per kb where as the 5’ UTR region showed 70 SNP, 8 BPS and 10 BPD per kb and 3’UTR showed 60 SNP, 9 BPS and 13 BPD per kb. There were significant differences even within the translated part of the genes as no BPS or BPDs were observed in the 25% of the genes at the C terminal of the proteins. After accounting for wheat codon usage, the 25.3% of the gene base pairs that are wobble, contained only the proportional 35% of the changes, ruling out the selection pressure being the primary cause of reduced changes in the translated part of the genes. Based on these results we postulate that wheat and perhaps other higher eukaryotes have a mechanism to protect ‘important’ parts of the genes from change. This hypothetical mechanism may utilize histone acetylation/methylation pattern that was observed to be unique for different parts of the genes and these unique patterns are consistent for the 5324 yeast genes (Pokholok et al., Cell 2005).