ISSN:
1615-6110
Keywords:
Brassiceae
;
Isozyme number
;
chromosome number
;
phylogeny
;
gene duplication
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Variation in isozyme number was used to assess the evolution of haploid chromosome numbers (n=6−75) and systematic relationships in the tribeBrassiceae, which is believed to be one of the few monophyletic tribes in theBrassicaceae. Ten enzyme systems were surveyed among 108 species in 35 genera of tribeBrassiceae and for 11 species from seven other tribes. The data indicated that taxa with n=7−13 and n=14−18 were similar in isozyme number, suggesting that genera with n=14−18 did not arise from polyploidy (i.e. entire duplication) of the n=7−13 genomes. These results suggest that aneuploidy and/or chromosome fusion/splitting have played a more significant role than polyploidy in the evolution of higher base chromosome numbers in the tribe. The detection of widespread isozyme duplication in the tribe is consistent with reports of extensive gene duplication in theBrassica crop species, and suggests that the common ancestor of the tribe already had undergone a polyploid event, i.e. complete genome duplication, prior to aneuploid divergence. Inheritance studies conducted onSinapis arvensis showed that segregation ratios at seven loci (Fbp-2,Gpi-2,Idh-2,Pgm-2,Pgm-2′,Tpi-1,Tpi-1′) conformed to those expected under Mendelian inheritance. Isozyme duplications were phylogenetically informative at various taxonomic levels in the tribe. In particular, duplications for cytosolic phosphoglucomutase (Pgm-2,Pgm-2′) and plastid triosephosphate isomerase (Tpi-1,Tpi-1′) were evident in 33 of the 35 genera examined, supporting the monophyletic status of theBrassiceae with the inclusion ofOrychophragmus and the exclusion of controversial membersCalepina andConringia.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00984659
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