No abstract

We employed a phylogenomic approach to study the evolution of alpha subunits of the proteasome gene family from early diverging eukaryotes. BLAST similarity searches of the Giardia lamblia genome identified all seven alpha proteasome genes characteristic of eukaryotes from the crown group. In addition, a PCR strategy for the amplification of multiple alpha subunit sequences generated single alpha proteasome products for representatives of the Kinetoplastida (Leishmania major), the Parabasalia (Trichomonas vaginalis), and the Microsporidia (Vairimorpha sp., Nosema sp., Endoreticulata sp., and Spraguea lophii). The kinetoplastid Trypanosoma cruzi and the eukaryote crown group Acanthamoeba castellanii yielded two distinct alpha proteasome genes each. The presence of seven distinct alpha proteasome genes in G. lamblia, one of the earliest-diverging eukaryotes, indicates that the alpha proteasome gene family evolved rapidly from a minimum of one gene in Archaea to seven or more in Eukarya. Results from the phylogenomic analysis are consistent with the idea that the Diplomonida (as represented by G. lamblia), the Kinetoplastida, the Parabasalia, and the Microsporidia diverged after the duplication events that originated the alpha proteasome gene family. A model for the early origin and evolution of the proteasome gene family is presented.

The existing sectional classification of the genus Crotalaria has merged the Indian sections Calycinae and Crotalaria under the section Calycinae Wight & Arn. emend. M.M.Le Roux & B.-E.van Wyk.Crotalaria subsection Bracteatae is re-evaluated to ascertain its position in the Calycinae clade. Evidences from morphological and molecular sequence data (ITS and trnL-F regions) are used to assess the subsectional position of Bracteatae. Within the recognized 12 species in the subsection, the morphological characters currently used to distinguish these species, are insignificant and overlapping and do not merit diagnostic characters of the species. Examination of the types and vouchers at different herbaria and specimens collected during field trips enabled us for a new interpretation of the existing circumscription of the species. Further, pod anatomical and molecular sequence data were also used for the delimitation of the species. Based on the results of the above studies, a new circumscription has been formalized here and contains five recognized species in the Bracteatae clade, viz., C. berteroana DC., C. longipes Wight & Arn., C. paniculata Willd., C. pulchra DC. and C. pellita DC. of the section Calycinae emend. M.M.Le Roux & B.-E.van Wyk. Crotalaria subsection Bracteatae appeared to be a well supported monophyletic group, but nested within the Calycinae clade. In order to maintain the monophyly of Crotalaria section Calycinae, Bracteatae is synonymized with the former.

No abstract