Immunolocalization of a novel annexin‐like protein encoded by a stress and abscisic acid responsive gene in alfalfa

Abstract

SummaryWe report here on the isolation and characterization of a full-length cDNA clone from alfalfa termed AnnMs2 encoding a 333 amino acid long polypeptide that shows 32-37% sequence identity with both mammalian and plant annexins, and has four tandem repeats. While other plant annexins exhibit a high level of sequence similarity to each other (up to 77% identity at amino acid level), AnnMs2 appears to be a distinct type of plant annexins. All the four endonexin folds contain the conserved eukaryotic motif within this alfalfa protein, but this element is considerably different in the second repeat. The AnnMs2 gene is expressed in various tissues of alfalfa with elevated mRNA accumulation in root and flower. This gene is activated in cells or tissues exposed to osmotic stress, abscisic acid (ABA) or water deficiency. The recombinant AnnMs2 protein is able to bind to phospholipid in the presence of Ca 2ϩ . Indirect immunofluorescence studies using affinity purified rabbit anti-AnnMs2 peptide antibody show mainly nucleolar localization, but the protein sequence lacks the usual nuclear localization signal. The potential role of this novel annexin-like protein in the basic and stress-induced cellular functions is discussed.

Over‐expression of the water and salt stress‐regulated Asr1 gene confers an increased salt tolerance

“…Many nuclear proteins can also be found in the cytosol (Yoneda 2000), and the translocation of proteins into and out of the nucleus can be employed by cells to regulate of the activity of such proteins. Induction of plant nuclear proteins by abiotic stresses has also been described previously (Godoy et al 1994;Kovacs et al 1998;Ascenzi & Gantt 1999;Munnik et al 1999;Castillo et al 2000;Scippa et al 2000). Not surprisingly, some of these proteins were also found localized both in the nucleus and cytosol (Godoy et al 1994;Houde et al 1995;Scippa et al 2000).…”

Abscisic Acid Biosynthesis and Response

“…This is accompanied by up to two-fold changes in membrane surface area, accomplished by vesicle secretion and endocytosis (reviewed in Schroeder et al, 2001). Consistent with this, ABA induces expression of an annexin-like gene (Kovacs et al, 1998), requires syntaxin function for normal ion channel response (Leyman et al, 1999) and reorganization of the actin cytoskeleton to a randomly oriented pattern (Eun and Lee, 1997).…”

The Role of Annexin 1 in Drought Stress in Arabidopsis

“…In contrast to previous reports (Kovacs et al, 1998;Cantero et al, 2006), we tested for expression changes in fully expanded leaves of 6-to 8-week-old plants. We found that AnnAt1 mRNA levels were significantly elevated after virtually all applied treatments, reaching the highest level and being the most sustained after treatment with ABA and during drought (Fig.…”

“…One of the first reports indicating a role for annexin in stress responses documented the up-regulation of an alfalfa (Medicago sativa) annexin in response to osmotic stress, abscisic acid (ABA), and drought (Kovacs et al, 1998). Transcriptome studies in Arabidopsis (Arabidopsis thaliana) have also revealed changes in annexin gene expression in response to a variety of abiotic stresses (Kreps et al, 2002).…”