Two bean cell wall proteins more abundant during water deficit are high in proline and interact with a plasma membrane protein

Abstract

SummaryTwo antigenically related glycoproteins, called p33 and p36, accumulate in the soluble fraction of the cell wall in response to water de®cit in Phaseolus vulgaris. In this report, we show that p33 and p36 are able to adhere to leaf protoplasts, and that they bind to plasma membrane (PM) vesicles in a divalent cationdependent manner. Data from the partial amino acid sequence of the p33 and p36 proteins indicate that they contain repeats of the decapeptide POVYKPOVEK; therefore, they are related to proline-rich proteins. Binding assays demonstrate that both proteins speci®cally bind to an 80 kDa PM protein. This binding is competed with a peptide that contains the RGD motif, as well as with ®bronectin, which also includes this sequence, suggesting that the 80 kDa PM protein has an integrin-like function whose natural ligands are p33 and p36. This is the ®rst case where a PM ligand for a higher plant cell wall protein has been identi®ed.

Mutations in the Arabidopsis Phosphoinositide Phosphatase Gene SAC9 Lead to Overaccumulation of PtdIns(4,5)P2 and Constitutive Expression of the Stress-Response Pathway

“…Cold and osmotic stress lead to changes in cell turgor pressure, profoundly affecting membrane structure (Ristic and Ashworth, 1993;Kubitscheck et al, 2000). Stress also induces expression of numerous cell walllocalized proteins thought to aid in stress tolerance, including extensins, Gly-and Pro-rich proteins, and annexins (Kovacs et al, 1998;Garcia-Gomez et al, 2000;Wu and Cosgrove, 2000;Bray, 2002;Lee et al, 2004). PtdIns(4,5)P 2 could play a role in stress response by reorganizing the actin cytoskeleton, affecting the targeting of vesicles or proteins to the plasma membrane or wall.…”

High affinity recognition of a Phytophthora protein by Arabidopsis via an RGD motif

“…Finally, the 80 kDa plasma membrane protein is an RGD binding protein capable of strong selectivity towards the RGD sequence. Only few RGD dependent protein-protein interactions have been described in plants [27][28], and their involvement in cell wall-membrane attachments remains to be elucidated. In contrast, the wall-associated kinases (WAKs) are bound to both the plasma membrane and the extracellular matrix [29], but these links are not mediated by an RGD sequence.…”

Transcriptional profiling of sunflower plants growing under low temperatures reveals an extensive down-regulation of gene expression associated with chilling sensitivity

“…Genes encoding PRPs have not been identified as being regulated by lowtemperature tolerance. However, an increase in PRP mRNA in response to water deficit has been observed (Creelman and Mullet, 1991;García-Gómez et al, 2000). It is well known that cell walls contain various types of proteins, including those highly enriched in proline residues (Cassab and Varner, 1988).…”

“…Because PRPs are presumably insoluble in the cell wall matrix, it has been suggested that they play a role in structural strengthening (Cassab, 1998). García-Gómez et al (2000) reported that PRPs interact with the plasma membrane through a specific protein, suggesting that PRPs may perform additional functions involving a contribution to the maintenance of a rigid adhesion of the plasma membrane to the cell wall. During development and environmental stress the composition and structure of the cell wall is continuously rearranged.…”