The identification of inducible cytoplasmic/nuclear carbohydrate-binding proteins urges to develop novel concepts about the role of plant lectins

Abstract

During the last few years compelling evidence has been presented for the occurrence of cytoplasmic/nuclear plant lectins that are not detectable in normal plants but are only induced upon application of well-defined stress conditions. Since both the regulation of the expression and the subcellular location indicate that these 'non-classical lectins' are good candidates to play a physiologically important role as mediators of specific protein-carbohydrate-interactions within the plant cell, a critical assessment is made of the impact of these findings on the development of novel concepts about the role of plant lectins. Based on an analysis of the biochemical, molecular and evolutionary data of a jasmonate-induced chitin-binding lectin from tobacco leaves and a salt/jasmonate-induced leaf lectin from rice it is concluded that these lectins most probably interact with endogenous glycans located within the cytoplasmic/nuclear compartment of the plant cell. Several working mechanisms are proposed to explain how these inducible lectins may fulfill an important regulatory or structural role in stressed cells. In addition, the question of the evolutionary relationship(s) between the newly discovered inducible lectins and their 'classical' constitutively expressed homologs is addressed. Evidence is presented that the 'non-classical lectins' represent the main evolutionary line and that some of their corresponding genes were used as templates for genes encoding storage protein-like 'classical' homologs.

Purification, partial characterization and antimicrobial activity of Lectin from Chenopodium Quinoa seeds

“…Lectins are defined as proteins/glycoproteins that have at least one domain with no catalytic properties that reversibly bind to some mono or oligosaccharides (Van Damme et al, 2003). The specific amino acid residues are essential for maintaining the carbohydrate binding and hemagglutinating activity of the lectins (Baiimiev et al, 2007).…”

Localization and in vitro binding studies suggest that the cytoplasmic/nuclear tobacco lectin can interact in situ with high‐mannose and complex N‐glycans

“…In addition, plant lectins and target glycoproteins are often expressed in different cells. Evidently, this reasoning does not apply to some recently identified plant lectins that reside in the cytoplasmic/nuclear compartment where they have access to physiologically important glycoproteins or other glycoconjugates [5]. One example of a cytoplasmic/nuclear lectin is the Nicotiana tabacum agglutinin, called Nictaba.…”

The Two DUF642 At5g11420 and At4g32460-Encoded Proteins Interact In Vitro with the AtPME3 Catalytic Domain

“…This group of proteins has interacting domains but does not show catalytic activity. The group presents with varying cellular localisation, which suggests a role in signal transduction between the different cellular compartments (Van Damme et al, 2004).…”