Howard M. Laten
Ph.D., 1978, Univ. of Wisconsin-Madison
My investigations are focused on the characterization and evolution of a unique family of plant retroelements that resemble mammalian retroviruses. Retroelements are a class of DNA and RNA genetic entities that utilize the enzyme reverse transcriptase to sponsor the replication of their small genomes. The best known retroelement is the human immunodeficiency virus, the causative agent of AIDS. Non-infectious retrotransposons constitute a second major class of retroelements and are found in virtually every eukaryote. While their genomes are similar to those of the retroviruses, they lack genes necessary for intercellular transfer. The proliferation of both classes of retroelements involves the integration of reverse transcribed DNA copies into the hosts' chromosomes. These copies become permanent residents (endogenous) and record present, past, and even ancient encounters with retroelements. Once considered by many to be pesky genetic parasites, these endogenous elements were dubbed "selfish DNA" because they can proliferate within chromosomes. However, they may actually be key players in the modification of host genomes during critical periods of large-scale evolutionary change.
The retroelement we discovered, SIRE-1, was first encountered in the soybean genome as a family of a thousand structurally conserved members with the standard complement of retroelement genes. But unlike other plant retroelements known at the time, SIRE-1 also codes for a protein unique to retroviruses -- an envelope-like protein. In retroviruses, the envelope protein confers infectivity. We have now confirmed the presence of SIRE-1 relatives in several other plant species, and expect it was once and may still be a highly successful retrovirus transmitted to plants by aphids or some other invertebrate vector.
Our attention is focused on three primary questions: 1) Is SIRE-1 an active plant retrovirus - do host cells make SIRE-1 mRNAs, proteins, virions? 2) Can invertebrate vectors be found? And 3) Can molecular systematic approaches reveal the precise evolutionary relationships among retroviruses and retrotransposons?
Laten, H.M. and A. Bousios (2011) The Sireviruses, In Springer Index of Viruses, Second Edition, C. Tidona and G. Darai, eds., in press.
Du, J., Z. Tian, C. Hans, H.M. Laten, S.A. Jackson, S.B. Cannon, R.C. Shoemaker & J. Ma. 2010. Evolutionary conservation, diversity and specificity of LTR-retrotransposons in flowering plants: new insights from genome-wide analysis and multi-specific comparison. The Plant Journal, in press.
Sobol, A. & Laten, H.M. 2009. GmGYPSY11 consensus sequence in Glycine max. Repbase Reports 9: 1380-1381.
Laten, H.M., L.S. Mogil & L.N. Wright. 2009. A shotgun approach to discovering and reconstructing consensus retrotransposons ex novo from dense contigs of short sequences derived from Genbank Genome Survey Sequence database records Gene 448: 168–173 [PMID: 19560526].
Flasch, D.A., E.K. Rebman, E.H. Olfson, K.K. Nguyen, L.E. Geirut, M.C. Garland, C.M. Lindorfer & H.M. Laten. 2008. Analysis of insertional sites of the SIRE1 retroelement family from Glycine max using GenBank BAC-end sequences. In Silico Biology 8: 531-543 [PMID: 19374136]
Laten, H.M., E. Gouvas, & E.B. Badal. 2008. GmOgre: Consensus sequence of an Ogre-like retrotransposon in Glycine max. Repbase Reports 8: 905-906.
Wright, L.N. & H.M. Laten. 2008. GmCOPIA11; a Copia-like retrotransposon from Glycine max. Repbase Reports 8: 903-904.
Mogil, L. & H.M. Laten. 2008. GmGYPSY10, a high copy number member of the Ty3-gypsy family of LTR retrotransposons from Glycine max. Repbase Reports 8: 685-686.
Wright, L.N. & H.M. Laten. 2008. GmCOPIA10; a Copia-like retrotransposon from Glycine max. Repbase Reports 8: 646-647.
Yano, S.T., B. Panbehi, A. Das & H.M. Laten. 2005. Diaspora, a large family of Ty3-gypsy retrotransposons in Glycine max, is an envelope-less member of an endogenous plant retrovirus lineage. BMC Evolutionary Biology 5: 30.1-30.14 (epub). [PMID: 15876351]
Grande, T., H.M. Laten & J.A. Lopez. 2004. Phylogenetic relationships of extant esocid species (Teleostei: Salmoniformes) based on morphological and molecular characters. Copeia 2004 (4): 743-757.
Laten, H.M., E.R. Havecker, L.M. Farmer & D.F. Voytas, 2003. “SIRE1, an endogenous retrovirus family from Glycine max, is highly homogeneous and evolutionarily young.” Molecular Biology and Evolution 20: 1222-1230. [PMID: 12777503]
Peterson-Burch, B.D., D.A. Wright, H.M. Laten &. D.F Voytas. 2000. “Retroviruses in Plants?” Trends in Genetics 16: 151-152. [PMID:10729827]
Laten, H.M. 1999. Phylogenetic evidence for Ty1-copia-like endogenous retroviruses in plant genomes. Genetica 107: 87-93. [PMID: 10952201]
Laten, H.M., A. Majumdar, & E.A. Gaucher. 1998. “SIRE-1, a Copia/Ty1-like Retroelement from Soybean, Encodes a Retroviral Envelope-like Protein,” Proceedings of the National Academy of Sciences USA 95: 6897-6902. [PMID:9618510]
Cladogram depicting SIRE-1's relationship to other retroelements.