Evidence for selection as a mechanism in the concerted evolution of @entity523 ( XXXX ) genes encoding the small subunit of @entity9578 carboxylase/oxygenase.

@entity286 @entity1522 @entity535 @entity377 @entity523 @entity9578 @entity9581
The nuclear gene sequences encoding RBCS, the small subunit of @entity9578 carboxylase/oxygenase (EC 4.1.1.39) from several plants show extensive interspecific divergence but little intraspecific divergence, suggesting that these genes are evolving in concert within a genome. In this study, the @entity377 sequences of two @entity523 ( @entity523 ) RBCS genes and a cDNA clone containing the entire coding region of a third @entity523 RBCS gene were determined. The three genes, designated Rbcs-1, @entity9581 , and Rbcs-3A, each belong to a different one of the three RBCS loci in the @entity523 genome. The @entity377 sequence of Rbcs-1 differs from that of @entity9581 and Rbcs-3A by 13.9% and 13.1%, respectively. @entity9581 and Rbcs-3A differ from each other by 10.7%. A recently published RBCS gene sequence from @entity286 ( @entity286 ) [Mazur, B. J. _ Chui, C.-F. (1985) Nucleic Acids Res. 13, 2373-2386] differs by 10.6% and 11.3% from @entity9581 and Rbcs-3A, respectively, and by 15.0% from Rbcs-1. Thus the @entity286 gene seems to be phylogenetically as closely related to the @entity523 genes @entity9581 and Rbcs-3A as the latter two are to each other, and more closely related to them than Rbcs-1 is. However, the mature part of the polypeptide encoded by the @entity286 RBCS gene differs by five and six @entity1522 from the corresponding region in the polypeptides encoded by @entity9581 and Rbcs-3A, respectively, while these two @entity523 RBCS polypeptides differ from each other in the mature part by a single @entity535 . Rbcs-1, whose @entity377 sequence shows higher divergence from both the @entity286 RBCS gene and @entity9581 and Rbcs-3A, encodes a polypeptide whose mature part differs by eight @entity1522 from the corresponding region in the @entity286 polypeptide but only by three and four @entity1522 from the corresponding regions of @entity9581 - and Rbcs-3A-encoded polypeptides, respectively. Thus, it appears that in the @entity523 selection has maintained near uniformity of the coding information in the portion of the RBCS genes encoding the mature polypeptides.
