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Abstract Detail


Genetics Section

Doyle, Jeff J. [1], Doyle, Jane L. [1].

Birth, silencing, and various degrees of death in the nuclear and mitochondrial paralogues of cytochrome oxidase subunit 2 of Glycine (Leguminosae).

Cytochrome oxidase subunit 2 (cox2) typically is encoded by a mitochondrial gene, but the gene is known to have been transferred to the nucleus in the legume lineage that includes Glycine (soybean and allies). Both the single nuclear copy (nu-cox2) and the mitochondrial copy (mt-cox2) have been shown to be expressed in soybean (G. max), but mt-cox2 is incompletely edited and is considered to be a pseudogene. We have found that most species of the other subgenus of Glycine (Glycine subgenus Glycine) possess two copies of nu-cox2. Phylogenetic analysis of nu-cox2 from several Glycine species representing both subgenera, along with outgroup genera, indicates that the duplication predated the divergence of the two subgenera of Glycine and likely was due to polyploidy. The same paralogue (Paralogue A) has been lost independently in the ancestor of the annual subgenus (G. subg. Soja, which includes the soybean) and in several different lineages of subg. Glycine. Some species possess truncated copies of Paralogue A, in which part of the target protein and intron have been deleted, whereas in other species Paralogue A has not been detected. Reverse transcript PCR (RT-PCR) experiments using conserved primers fail to reveal expression of Paralogue A in leaves of any Glycine species, even those that possess both nuclear paralogues, whereas both nu-cox2 Paralogue B and mt-cox2 are expressed. These results suggest that Paralogue A may have been silenced prior to the divergence of the two subgenera, after which it suffered partial or complete deletion. The fate of mt-cox2 has varied in the genus, with evidence suggesting that it is still properly edited in species of subg. Glycine and thus may be functional.


1 - Cornell University, L.H. Bailey Hortorium, Department of Plant Biology, Ithaca, New York, 14853, U.S.A.

Keywords:
cox2
duplication
polyploidy
Glycine
silencing
birth and death.

Presentation Type: Paper
Session: 53-9
Location: Peruvian (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 3:15 PM
Abstract ID:124


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