<p>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p> <p>Data from cytological and genetic mapping studies suggest that maize arose as
a tetraploid. Two previous studies investigating the most likely mode of maize
origin arrived at different conclusions. Gaut and Doebley [7] proposed a segmental
allotetraploid origin of the maize genome and estimated that the two maize
progenitors diverged at 20.5 million years ago (mya). In a similar study, using larger
data set, Brendel and colleagues (quoted in [8]) suggested a single genome duplication
at 16 mya. One of the key components of such analyses is to examine sequence
divergence among strictly orthologous genes. In order to identify such genes, Lai
and colleagues [10] sequenced five duplicated chromosomal regions from the maize
genome and the orthologous counterparts from the sorghum genome. They also
identified the orthologous regions in rice. Using positional information of genetic
components, they identified 11 orthologous genes across the two duplicated regions
of maize, and the sorghum and rice regions. Swigonova <italic>et al</italic>. [12] analyzed the 11
orthologues, and showed that all five maize chromosomal regions duplicated at the
same time, supporting a tetraploid origin of maize, and that the two maize progenitors
diverged from each other at about the same time as each of them diverged from
sorghum, about 11.9 mya.</p>
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Comp Funct Genomics. 2004 Apr; 5(3):281-284