Comparative genetics in the grasses - PubMed (original) (raw)

Comparative genetics in the grasses

M D Gale et al. Proc Natl Acad Sci U S A. 1998.

Abstract

Genetic mapping of wheat, maize, and rice and other grass species with common DNA probes has revealed remarkable conservation of gene content and gene order over the 60 million years of radiation of Poaceae. The linear organization of genes in some nine different genomes differing in basic chromosome number from 5 to 12 and nuclear DNA amount from 400 to 6,000 Mb, can be described in terms of only 25 "rice linkage blocks." The extent to which this intergenomic colinearity is confounded at the micro level by gene duplication and micro-rearrangements is still an open question. Nevertheless, it is clear that the elucidation of the organization of the economically important grasses with larger genomes, such as maize (2n = 10, 4,500 Mb DNA), will, to a greater or lesser extent, be predicted from sequence analysis of smaller genomes such as rice, with only 400 Mb, which in turn may be greatly aided by knowledge of the entire sequence of Arabidopsis, which may be available as soon as the turn of the century. Comparative genetics will provide the key to unlock the genomic secrets of crop plants with bigger genomes than Homo sapiens.

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Figures

Figure 1

Figure 1

A consensus grass comparative map. The comparative data have been drawn from many sources: Oats-wheat-maize-rice (8); wheat-rice (6, 30), and unpublished data; maize-rice (5, 10); maize-wheat (7); maize-sorghum-sugarcane (10, 11); and foxtail millet-rice (9). Arrows indicate inversions and transpositions necessary to describe present-day chromosomes. Locations of telomeres (▵) and centromeres (□) are shown where known. Hatched areas indicate chromosome regions for which very little comparative data exist. Chromosome nomenclatures and arm (short/long or top/bottom) designations are as described by O’Donoughue et al. (31) for oats, Pereira et al. (32) for sorghum, Dufour (11) for the sugarcane genomes, Wang et al. (33) in foxtail millet, and Singh et al. (34) in rice.

Figure 2

Figure 2

Comparative maps of the wheat genome described in terms of the rice genome (A) and the Ae. umbellulata genome (B). (A) Data from Kurata et al. (6), Van Deynze et al. (30), and unpublished work. (B) Data from Zhang et al. (9).

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