IMIBIO-SL   20937
INSTITUTO MULTIDISCIPLINARIO DE INVESTIGACIONES BIOLOGICAS DE SAN LUIS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Alternative models about the origin of Ribosome Inactivating Proteins genes
Autor/es:
LAPADULA W.J.; SANCHEZ-PUERTA M.V.; JURI AYUB M
Reunión:
Congreso; 3er congreso Argentino de Bioinformática y Biología Computacional; 2012
Resumen:
Ribosome inactivating proteins (RIPs) are N-glycosidases that depurinate a specific adenine residue in the
conserved sarcin/ricin loop of 28S rRNA. The most widely studied examples of RIPs are ricin, a potent toxin of
Ricinus communis, and Shiga toxins from enteric bacteria causing hemolytic uremic syndrome. RIPs genes have
been reported to be present in many plants and a few bacteria. In addition, there are biochemical evidences of
RIP activity in a few fungi species. The analysis of RIPs phylogeny is problematic because the sequences are highly
divergent, and their distribution across species is patchily distributed. It is currently assumed that RIPs genes
were originated in plants and prokaryotic RIPs have been acquired by a single Horizontal Gene Transfer (HGT)
event from plant to bacteria [1]. We have recently reported a phylogenetic analysis of RIP sequences [2]. In the
present work, we performed exhaustive searches for novel RIP genes in genomic and EST databases. We found
novel RIP encoding sequences from bacteria, and more interestingly, eleven RIP genes in fungal WGS. These
results suggest that the current view of RIPs phylogeny should be revisited. Therefore, we performed sequence
alignments using different algorithms (CLUSTALW, T-COFEE, MAFFT), and new phylogeny inferences including the
novel sequences. The resulting data were analyzed in the context of phylogenetic relationships among species, in
order to propose the most plausible hypothesis. Altogether, the data can be explained by at least two alternative
models (see Figure 1):
I. RIPs genes originated in plants and were acquired via HGT by fungi and bacteria. This model implies at
least three independent HGT events.
II. RIPs genes were present in the common ancestor of eukaryotes and bacteria, and were lost in several
lineages through evolution. This model implies several loss events in different lineages; archaea, metazoan,
many bacteria, etc.
The pros and cons of these models are discussed in this work.
Figure