Cotton fiber annexins: a potential role in the regulation of callose synthase

Abstract

SummaryCotton fibers contain a characteristic set of proteins which interact with plasma membranes in a Ca2+-dependent manner. The association of these proteins with the membrane is correlated with a reduced level of UDP-glucose: (1+3)-p-glucan (callose) synthase activity. Analysis of the proteins released from membranes by EDTA treatment shows that the most abundant proteins comprise a family of at least three polypeptides (p34) which resemble annexins. This resemblance includes similarity in size (about 34 kDa), sequence homology, Ca*+-dependent precipitation or interaction with the plasma membrane, and ability to serve as a substrate for phosphorylation by endogenous protein kinase(s) which also bind to the membranes in a Ca*+-dependent manner. A purified fraction of these annexins binds to, and inhibits, the activity of a partially purified cotton fiber callose synthase. These findings suggest that one possible function of annexin(s) in plants is to modulate the activity and/or localization of callose synthase.

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

“…From a functional point of view, plant annexins have been implicated in Ca 2ϩ -dependent exocytosis , regulation of callose synthase activity in cotton fibers (Andrawis et al, 1993), Ca 2ϩ signal transduction events in the vacuole (Seals et al, 1994), and in the interaction with actin (Calvert et al, 1996). Some of the plant annexins have been shown to possess intrinsic phosphodiesterase activity (Calvert et al, 1996;McClung et al, 1994).…”

Annexins of Plant Cells

“…Vol. 109, 1995 In pea plumules a single 35-kD annexin band on SDS-PAGE yields three isoforms with pls of 6.5, 6.8, and 7.0 when subjected to two-dimensional gel analysis, and in cotton fibers the 34-kD annexin band is made up of three isoforms ranging from pI of 6.1 to 6.5 (Clark et al, 1992;Andrawis et al, 1993). These different isoforms may represent a single gene product that has undergone posttranslational modification, such as phosphorylation, or different gene products, such as seen in rat liver, where three different annexin gene products co-migrate at 35 kD on SDS-PAGE (Kaetzel et al, 1989).…”

“…Peptide sequences obtained from tomato (Smallwood et al, 1990), corn (Blackbourn et al, 19921, pea (Clark et al, 19921, and cotton (Andrawis et al, 1993) proteins a11 indicated a degree of primary sequence conservation between plant and animal annexins. In animal cells most of the annexins are acetylated on their N terminus, although there is one report of an annexin with a myristolated N terminus (Wice and Gordon, 1992).…”

“…It will also be interesting to determine whether actin or phospholipids stimulate/inhibit the ATPase activity associated with maize annexins. Andrawis et al (1993) described a 34-kD annexin in cotton fibers that inhibits the activity of callose synthase, a plasma membrane-localized enzyme. The inhibition of activity is apparently due to a direct interaction of the 34-kD annexin with the enzyme, but further experiments will be needed to confirm that callose synthase is a molecular binding partner of the 34-kD annexin.…”

“…Annexin V forms trimers, hexamers, and higher aggregates in the presence of Ca2+ and anionic phospholipids. The formation of annexin multimer sheets on the surface of a membrane is proposed to alter membrane properties such as fluidity and phospholipid segregation, which in turn can affect membrane protein function (Andree et al, 1992;Concha et al, 1992). It appears that plant annexins may share this property, based on a report that a 35-kD annexin purified from green peppers forms homodimers during the process of vesicle aggregation (Hoshino et al, 1995).…”