Abstract
SH3P2 (At4g34660), an Arabidopsis thaliana SH3 and Bin/amphiphysin/Rvs (BAR) domain-containing protein, was reported to have a specific role in cell plate assembly, unlike its paralogs SH3P1 (At1g31440) and SH3P3 (At4g18060). SH3P family members were also predicted to interact with formins—evolutionarily conserved actin nucleators that participate in microtubule organization and in membrane–cytoskeleton interactions. To trace the origin of functional specialization of plant SH3Ps, we performed phylogenetic analysis of SH3P sequences from selected plant lineages. SH3Ps are present in charophytes, liverworts, mosses, lycophytes, gymnosperms, and angiosperms, but not in volvocal algae, suggesting association of these proteins with phragmoplast-, but not phycoplast-based cell division. Separation of three SH3P clades, represented by SH3P1, SH3P2, and SH3P3 of A. thaliana, appears to be a seed plant synapomorphy. In the yeast two hybrid system, Arabidopsis SH3P3, but not SH3P2, binds the FH1 and FH2 domains of the formin FH5 (At5g54650), known to participate in cytokinesis, while an opposite binding specificity was found for the dynamin homolog DRP1A (At5g42080), confirming earlier findings. This suggests that the cytokinetic role of SH3P2 is not due to its interaction with FH5. Possible determinants of interaction specificity of SH3P2 and SH3P3 were identified bioinformatically.
Highlights
In land plants, cytokinesis is a result of a precisely orchestrated sequence of events that include rearrangements of actin and microtubule cytoskeletons, leading to post-anaphase assembly of the microtubular scaffolding of the phragmoplast at a position that has been previously marked by an “actin-depleted zone”, i.e., an area largely devoid of microfilaments, whose location, in turn, reflects that of the microtubular preprophase band [1,2,3]
Streptophyte algae perform a variant of phragmoplast-based cytokinesis [7], while chlorophyte algae such as Chlamydomonas divide their cells by cleavage, employing a different microtubule-based structure termed the phycoplast [8]
It is found in proteins of signaling pathways regulating the cytoskeleton, modulating membrane dynamics, or serving as adaptors that link metazoan tyrosine kinases to specific target proteins
Summary
Cytokinesis is a result of a precisely orchestrated sequence of events that include rearrangements of actin and microtubule cytoskeletons, leading to post-anaphase assembly of the microtubular scaffolding of the phragmoplast at a position that has been previously marked by an “actin-depleted zone”, i.e., an area largely devoid of microfilaments, whose location, in turn, reflects that of the microtubular preprophase band [1,2,3]. Besides its association with clathrin-coated vesicles, SH3P2 localizes to autophagosomes, participates in the membrane deformation process during autophagosome formation, and interacts with the autophagy-related protein ATG8 [24,25]. Inducible RNAi knockdown of SH3P2 suppresses formation of autophagosomes and brings about root growth arrest, premature cotyledon senescence, and subsequent seedling lethality [24] Both SH3P2 and SH3P3 bind FYVE1, a FYVE domain protein participating in autophagy, degradation of ubiquitinated membrane proteins, and vacuole biogenesis [22]. Unlike the endocytosis- and autophagy-related functions, which involve more than one member of the SH3P protein family, the cytokinetic role of SH3P2 is specific to this SH3P paralog. Our results contribute to characterization of the functional diversity of Arabidopsis SH3Ps and to understanding the origins of the “cytokinetic” SH3P2 type of plant SH3Ps
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
