Little data is available on microsatellite dynamics in the duplicated regions of the rice genome, even though efforts have been made in the past to align genome sequences of its two sub-species. Based on the coordinates of duplicated sequences in the indica genome as available in the public domain, we identified microsatellites in these regions. CCG and GAAAA repeats occurred most frequently. In all, 259 microsatellites could be identified in the duplicated sequences using the criteria of minimum 90% alignability spread over a minimum of 1?Kb sequence. More than 25% of the repeats in duplicated regions occurred in the genic sequences. Only 45 (17%) of these 259 microsatellites were found conserved in the duplicated paralogues. Among these repeats, 40% maintained both sequence and length conservation. The effect of mutability of nearby regions could also be clearly seen in microsatellite regions. The overall purpose of this study was to investigate, whether microsatellites follow an independent course of evolutionary dynamics subsequent to events like genome reshuffling that simply drives these elements to different locations in the genome. To the best of our knowledge, this is the first comprehensive analysis of microsatellite conservation in the duplicated regions of any genome. 1. Introduction Microsatellites represent a class of tandem DNA repeats with 1 to 6?bp long repeat units. These sequences occur in almost all the organisms and frequently constitute the hypervariable regions of the genome. No specific functions have been assigned to most of the microsatellites till date. However, in some cases at least, microsatellite alleles provide protective or adaptive advantage to the host [1]. In many cases, occurrence of different alleles has been found associated with different phenotypes [2]. Microsatellites are not expected to be conserved for long evolutionary periods either, as argued by Buschiazzo and Gemmell [3]. Nevertheless, models of microsatellite mutational dynamics have been developed based on comparison of orthologous microsatellite loci in related taxa [4–7]. However, whether these models also describe microsatellites at paralogous loci created by segmental changes within a genome remains to be investigated. Availability of whole-genome sequences for rice (Oryza sativa L.) allows analysis of noncoding DNA also within the segmentally duplicated regions in addition to the gene order, tandemly arranged genes (TAGs) and gene functions. A collective look emerging from different reports on mapping of duplicated regions in rice genome [8–10]
References
[1]
Y. Kashi and D. G. King, “Simple sequence repeats as advantageous mutators in evolution,” Trends in Genetics, vol. 22, no. 5, pp. 253–259, 2006.
[2]
J. B. W. Wolf, C. Harrod, S. Brunner, S. Salazar, F. Trillmich, and D. Tautz, “Tracing early stages of species differentiation: ecological, morphological and genetic divergence of Galápagos sea lion populations,” BMC Evolutionary Biology, vol. 8, article 150, 2008.
[3]
E. Buschiazzo and N. J. Gemmell, “Conservation of human microsatellites across 450 million years of evolution,” Genome Biology and Evolution, vol. 2, pp. 153–165, 2010.
[4]
T. Barbará, C. Palma-Silva, G. M. Paggi, F. Bered, M. F. Fay, and C. Lexer, “Cross-species transfer of nuclear microsatellite markers: potential and limitations,” Molecular Ecology, vol. 16, no. 18, pp. 3759–3767, 2007.
[5]
A. Grover, V. Aishwarya, and P. C. Sharma, “Biased distribution of microsatellite motifs in the rice genome,” Molecular Genetics and Genomics, vol. 277, no. 5, pp. 469–480, 2007.
[6]
A. Grover, B. Ramesh, and P. C. Sharma, “Development of microsatellite markers in potato and their transferability in some members of Solanaceae,” Physiology and Molecular Biology of Plants, vol. 15, no. 4, pp. 343–358, 2009.
[7]
M. Roorkiwal, A. Grover, and P. C. Sharma, “Genome-wide analysis of conservation and divergence of microsatellites in rice,” Molecular Genetics and Genomics, vol. 282, no. 2, pp. 205–215, 2009.
[8]
R. Guyot and B. Keller, “Ancestral genome duplication in rice,” Genome, vol. 47, no. 3, pp. 610–614, 2004.
[9]
X. Wang, X. Zhao, J. Zhu, and W. Wu, “Genome-wide investigation of intron length polymorphisms and their potential as molecular markers in rice (Oryza sativa L.),” DNA Research, vol. 12, no. 6, pp. 417–427, 2005.
[10]
J. Yu, J. Wang, W. Lin, et al., “The genomes of Oryza sativa: a history of duplications,” PLoS Biology, vol. 3, no. 2, article e38, pp. 266–281, 2005.
[11]
D. Retelska, E. Beaudoing, C. Notredame, C. V. Jongeneel, and P. Bucher, “Vertebrate conserved non coding DNA regions have a high persistence length and a short persistence time,” BMC Genomics, vol. 8, article 398, 2007.
[12]
S. F. Altschul, T. L. Madden, A. A. Sch?ffer et al., “Gapped BLAST and PSI-BLAST: a new generation of protein database search programs,” Nucleic Acids Research, vol. 25, no. 17, pp. 3389–3402, 1997.
[13]
M. Brudno, S. Malde, A. Poliakov et al., “Glocal alignment: finding rearrangements during alignment,” Bioinformatics, vol. 19, supplement 1, pp. i54–i62, 2003.
[14]
K. A. Frazer, L. Pachter, A. Poliakov, E. M. Rubin, and I. Dubchak, “VISTA: computational tools for comparative genomics,” Nucleic Acids Research, vol. 32, supplement 2, pp. W273–W279, 2004.
[15]
L. Zhang, H. H. S. Lu, W. Y. Chung, J. Yang, and W. H. Li, “Patterns of segmental duplication in the human genome,” Molecular Biology and Evolution, vol. 22, no. 1, pp. 135–141, 2005.
[16]
P. C. Sharma, A. Grover, and G. Kahl, “Mining microsatellites in eukaryotic genomes,” Trends in Biotechnology, vol. 25, no. 11, pp. 490–498, 2007.
[17]
A. Bhargava and F. F. Fuentes, “Mutational dynamics of microsatellites,” Molecular Biotechnology, vol. 44, no. 3, pp. 250–266, 2010.
[18]
A. Grover and P. C. Sharma, “Is spatial occurrence of microsatellites in the genome a determinant of their function and dynamics contributing to genome evolution?” Current Science, vol. 100, no. 6, pp. 859–869, 2011.
[19]
The Rice Chromosomes 11 and 12 Sequencing Consortia, “The sequence of rice chromosomes 11 and 12, rich in disease resistance genes and recent gene duplications,” BMC Biology, vol. 3, article 20, 2005.
[20]
J. W. Fondon III and H. R. Garner, “Molecular origins of rapid and continuous morphological evolution,” Proceedings of the National Academy of Sciences of the United States of America, vol. 101, no. 52, pp. 18058–18063, 2004.
[21]
J. M. Hancock and M. Simon, “Simple sequence repeats in proteins and their significance for network evolution,” Gene, vol. 345, no. 1, pp. 113–118, 2005.
[22]
D. E. Riley and J. N. Krieger, “UTR dinucleotide simple sequence repeat evolution exhibits recurring patterns including regulatory sequence motif replacements,” Gene, vol. 429, no. 1-2, pp. 80–86, 2009.
[23]
C. Schl?tterer, “Hitchhiking mapping—functional genomics from the population genetics perspective,” Trends in Genetics, vol. 19, no. 1, pp. 32–38, 2003.
[24]
C. Schl?tterer, M. Kauer, and D. Dieringer, “Allele excess at neutrally evolving microsatellites and the implications for tests of neutrality,” Proceedings of the Royal Society B Biological Science, vol. 271, no. 1541, pp. 869–874, 2004.
[25]
C. A. Driscoll, M. Menotti-Raymond, G. Nelson, D. Goldstein, and S. J. O'Brien, “Genomic microsatellites as evolutionary chronometers: a test in wild cats,” Genome Research, vol. 12, no. 3, pp. 414–423, 2002.
[26]
M. Brandstr?m and H. Ellegren, “Genome-wide analysis of microsatellite polymorphism in chicken circumventing the ascertainment bias,” Genome Research, vol. 18, no. 6, pp. 881–887, 2008.
[27]
M. Brandstr?m, A. T. Bagshaw, N. J. Gemmell, and H. Ellegren, “The relationship between microsatellite polymorphism and recombination hot spots in the human genome,” Molecular Biology and Evolution, vol. 25, no. 12, pp. 2579–2587, 2008.