Abstract
BackgroundInvolvement of conservative molecular modules and cellular mechanisms in the widely diversified processes of eukaryotic cell morphogenesis leads to the intriguing question: how do similar proteins contribute to dissimilar morphogenetic outputs. Formins (FH2 proteins) play a central part in the control of actin organization and dynamics, providing a good example of evolutionarily versatile use of a conserved protein domain in the context of a variety of lineage-specific structural and signalling interactions.ResultsIn order to identify possible plant-specific sequence features within the FH2 protein family, we performed a detailed analysis of angiosperm formin-related sequences available in public databases, with particular focus on the complete Arabidopsis genome and the nearly finished rice genome sequence. This has led to revision of the current annotation of half of the 22 Arabidopsis formin-related genes. Comparative analysis of the two plant genomes revealed a good conservation of the previously described two subfamilies of plant formins (Class I and Class II), as well as several subfamilies within them that appear to predate the separation of monocot and dicot plants. Moreover, a number of plant Class II formins share an additional conserved domain, related to the protein phosphatase/tensin/auxilin fold. However, considerable inter-species variability sets limits to generalization of any functional conclusions reached on a single species such as Arabidopsis.ConclusionsThe plant-specific domain context of the conserved FH2 domain, as well as plant-specific features of the domain itself, may reflect distinct functional requirements in plant cells. The variability of formin structures found in plants far exceeds that known from both fungi and metazoans, suggesting a possible contribution of FH2 proteins in the evolution of the plant type of multicellularity.
Highlights
Involvement of conservative molecular modules and cellular mechanisms in the widely diversified processes of eukaryotic cell morphogenesis leads to the intriguing question: how do similar proteins contribute to dissimilar morphogenetic outputs
A phosphatase/tensin/PTEN-related domain in most Class II formins While screening for known domains in plant formins using the SMART package [44], we found a significant match to the undefined specifity protein phosphatase domain (PTPc_DSPc, SM0012, BLAST E = 9. 10-6) in the N-terminal part of AtFH18
One of the most intriguing questions of contemporary molecular biology is how can vastly dissimilar organisms develop utilizing a limited repertoire of basically similar molecules derived from a relatively small set of conserved protein domains? Processes of eukaryotic cell morphogenesis, such as shaping of the actin cytoskeleton, provide a good example of such a versatile usage of conserved molecular mechanisms
Summary
Involvement of conservative molecular modules and cellular mechanisms in the widely diversified processes of eukaryotic cell morphogenesis leads to the intriguing question: how do similar proteins contribute to dissimilar morphogenetic outputs. The FH2 domain, whose structure has been recently determined [14,15], acts as a dimer, nucleating new actin filaments by a novel Arp2/3 independent mechanism, which has been well documented in both yeast and metazoans [16,17,18,19]. This provides a mechanistic basis for the observed morphogenetic role of formins. Other formins communicate with universal "adaptor" domains such as SH3 or WW
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