Annexins

Abstract

SummaryAnnexins are multifunctional lipid-binding proteins. Plant annexins are expressed throughout the life cycle and are under environmental control. Their association or insertion into membranes may be governed by a range of local conditions (Ca 2+ , pH, voltage or lipid identity) and nonclassical sorting motifs. Protein functions include exocytosis, actin binding, peroxidase activity, callose synthase regulation and ion transport. As such, annexins appear capable of linking Ca 2+ , redox and lipid signalling to coordinate development with responses to the biotic and abiotic environment. Significant advances in plant annexin research have been made in the past 2 yr. Here, we review the basis of annexin multifunctionality and suggest how these proteins may operate in the life and death of a plant cell.

Arabidopsis Annexin1 Mediates the Radical-Activated Plasma Membrane Ca2+- and K+-Permeable Conductance in Root Cells

“…in Laohavisit and Davies, 2011a;Konopka-Postupolska et al, 2011). The ligon mutant of cotton (Gossypium hirsutum) is impaired in fiber elongation, and proteomic analysis revealed significant downregulation of five annexin isoforms when compared with the wild type, consistent with roles for annexins in growth (Zhao et al, 2010).…”

“…However, no studies have causally linked in vitro annexin transport activity to that in native membrane (KonopkaPostupolska et al, 2011). Annexins are abundant throughout the plant kingdom (reviewed in Laohavisit and Davies, 2011a), and some contain the charged residues found in the hydrophobic pore of channel-forming animal annexins (Kourie and Wood, 2000;Laohavisit et al, 2009;Laohavisit and Davies, 2011a). Of these, Capsicum annuum annexin32/24 (ANN32/24) mediates Ca 2+ influx in liposomes (Hofmann et al, 2000), while maize annexins ANN33 and ANN35 support a Ca 2+ -permeable conductance in planar lipid bilayers (PLBs) (Laohavisit et al, 2009(Laohavisit et al, , 2010, and Arabidopsis ANN1 forms a K + -permeable channel in PLB (Gorecka et al, 2007).…”

“…annexins have been proposed to act as sensors of stress and stress-evoked ROS (Gorecka et al, 2007;Laohavisit et al, 2010;Laohavisit and Davies, 2011a). In roots of Arabidopsis under salt stress, preventing the formation of or scavenging OH _ compromises the stability of the newly made mRNAs encoding for the PM Na + /H + exporter Salt Overly Sensitive1 (SOS1; Chung et al, 2008).…”

Multivesicular Bodies Mature from the Trans-Golgi Network/Early Endosome in Arabidopsis

“…On the basis of our EM data, showing MVBs/LEs containing bottleneck structures after ConcA washout, it is tempting to speculate that such structures might be a target for annexin action. However, the function of plant annexins with respect to the modulation of membrane dynamics remains to be established (Laohavisit and Davies, 2011).…”

Insight into plant annexin function

“…Alternatively, Ntann12 may promote other proteins to bind tightly to a membrane, forming a 'multidomain cooperation'. 5 Since in root cells, Ntann12 is mainly localized in the nucleus, it is tempting to speculate that at least one of the Ntann12-protein partner's possess a nuclear localization signal that help the complex to reach the cell nucleus. Another possibility is that Ntann12 could be modified by ubiquitination and/or sumoylation, which are involved in nucleo-cytoplasmic trafficking (for a review see ref.…”