Adrienne Elizabeth Clarke

Hydroxyproline-rich plant glycoproteins

This review summarizes the structures of the four major groups of hydroxyproline-rich glycoproteins from plants; extensins, proline/hydroxyproline-rich glycoproteins, arabinogalactan-proteins, and solanaceous lectins. Similarities and differences within and between the groups are discussed.

Studies on the cell surface of zoospores and cysts of the fungus Phytophthora cinnamomi: nature of the surface saccharides as determined by quantitative lectin binding studies.

The nature of the surface saccharides of zoospores, partially encysted zoospores and cysts of the root-rotting fungus Phytophthora cinnamomi, has been examined by quantitative lectin binding studies. Zoospores bound concanavalin A (Con A), but did not bind any of a variety of other lectins tested. In contrast, both cysts and partially encysted zoospores bound soybean agglutinin (SBA) as well as Con A. This indicates that accessible alpha-D-glucosyl/alpha-D-mannosyl-containing glycoconjugates predominate at the zoospore surface, whereas both alpha-D-glucosyl/alpha-D-mannosyl and galactosyl and/or N-acetyl-D-galactosaminosyl residues are accessible at the surface of cysts and partially encysted zoospores. Neither Ulex europeus lectin nor wheat germ agglutinin (WGA) bound to any of the three cell preparations, indicating the absence of accessible alpha-L-fucosyl and N-acetyl-D-glucosaminosyl residues.

Influence of α-Helices on the Emulsifying Properties of Proteins

A peptide derived from apomyoglobin by cyanogen bromide cleavage was found to be an active emulsifier. This molecule, peptide 1-55, has two potential amphipathic α-helices and a hydrophilic C-terminal domain. The importance of this molecule was investigated by testing the products of gene constructs based on the sequence of peptide 1-55, but lacking one of the three domains. The emulsifying activity of the peptides lacking either of the α-helices was correlated with the hydrophobic moments of their respective helices. The hydrophobic moment is a measure of the amphipathicity of α-helices; a hydrophobic moment analysis of other emulsifying peptides supports the hypothesis that a high hydrophobic moment contributes to good emulsifying properties in a molecule which contains α-helices.

Molecular Genetics of Self-incompatibility in Nicotiana alata

Self-incompatibility is a genetically controlled mechanism which prevents inbreeding in plants (de Nettancourt, 1977). In many, but not all cases, it is controlled by a multi-allelic, single gene, the S-gene. The system operates to enhance outcrossing and to ensure that a plant is fertilized by a genetically distinct individual of the same species. There are two major types of self-incompatibility. The most widespread is gametophytic self-incompatibility which involves interaction of a product of the haploid genome of the male gametophyte (carried within the pollen grain) and a product of the diploid genome of the female tissue of the sporophyte, the pistil. In incompatible matings, as is the case when the S-allele carried by the haploid pollen matches either of the S-alleles present in the diploid style, pollen tube growth is arrested within the transmitting tract (Figure 1).