The Role of Annexin 1 in Drought Stress in Arabidopsis  

Abstract

Annexins act as targets of calcium signals in eukaryotic cells, and recent results suggest that they play an important role in plant stress responses. We found that in Arabidopsis (Arabidopsis thaliana), AnnAt1 (for annexin 1) mRNA levels were upregulated in leaves by most of the stress treatments applied. Plants overexpressing AnnAt1 protein were more drought tolerant and knockout plants were more drought sensitive than ecotype Columbia plants. We also observed that hydrogen peroxide accumulation in guard cells was reduced in overexpressing plants and increased in knockout plants both before and after treatment with abscisic acid. Oxidative protection resulting from AnnAt1 overexpression could be due to the low level of intrinsic peroxidase activity exhibited by this protein in vitro, previously linked to a conserved histidine residue found in a peroxidase-like motif. However, analyses of a mutant H40A AnnAt1 protein in a bacterial complementation test and in peroxidase activity assays indicate that this residue is not critical to the ability of AnnAt1 to confer oxidative protection. To further examine the mechanism(s) linking AnnAt1 expression to stress resistance, we analyzed the reactive S3 cluster to determine if it plays a role in AnnAt1 oligomerization and/or is the site for posttranslational modification. We found that the two cysteine residues in this cluster do not form intramolecular or intermolecular bonds but are highly susceptible to oxidation-driven S-glutathionylation, which decreases the Ca 2+ affinity of AnnAt1 in vitro. Moreover, S-glutathionylation of AnnAt1 occurs in planta after abscisic acid treatment, which suggests that this modification could be important in regulating the cellular function of AnnAt1 during stress responses.

Proteomic Study of Low-Temperature Responses in Strawberry Cultivars (Fragaria×ananassa) That Differ in Cold Tolerance

“…Interestingly, distinct annexin1 isoforms were found in 'Jonsok' and 'Frida'. The difference in mass and charge may be due to posttranslational glutathionylation as observed in Arabidopsis (Konopka-Postupolska et al, 2009). …”

“…Arabidopsis annexin1 has peroxidase activity and overexpression and knockout experiments have demonstrated a significant contribution to stress tolerance (Konopka-Postupolska et al, 2009). Interestingly, distinct annexin1 isoforms were found in 'Jonsok' and 'Frida'.…”

Annexins: Components of the Calcium and Reactive Oxygen Signaling Network

“…Manipulation of AtANN1 abundance inversely correlates with abscisic acidinduced ROS accumulation in guard cells, but the mode of action remains unclear (Konopka-Postupolska et al, 2009). It has been proposed that annexin peroxidase activity could protect membranes against peroxidation (Jami et al, 2008) or locally terminate a peroxide-based signal in membrane microdomains ).…”

“…The stress conditions that increase plant annexin abundance and recruitment to membranes (e.g. exogenous abscisic acid, drought, salinity, metal stress [Bianchi et al, 2002;Repetto et al, 2003;Lee et al, 2004;Vandeputte et al, 2007;Konopka-Postupolska et al, 2009]) can also result in ROS production (Demidchik et al, 2003;Boudsocq and Laurière, 2005;Konopka-Postupolska et al, 2009;Rodríguez-Serrano et al, 2009) and the lipid peroxidation that is typified by increases in MDA content (Demiral and Turkan, 2005;Collin et al, 2008). This suggests that annexins could function in integrating ROS and Ca 2+ in stress signaling.…”

“…Annexin involvement in such pathways is likely to be complex, as the annexins identified to date as transport competent (CaANN24, ZmANN33/35, and Arabidopsis thaliana annexin 1 [AtANN1]) also exhibit peroxidase activity in soluble or membrane-bound form (Hofmann et al, 2000;Gorecka et al, 2007;Konopka-Postupolska et al, 2009;Mortimer et al, 2009). Manipulation of AtANN1 abundance inversely correlates with abscisic acidinduced ROS accumulation in guard cells, but the mode of action remains unclear (Konopka-Postupolska et al, 2009).…”