Role of phytolectin in the life cycle of plants

Structural and functional analysis of a novel galactose-binding lectin derived from Chlorella sorokiniana MW769776

A freshwater green microalgal strain was isolated and the lectin was identified in it by a strong hemagglutination activity (HA) assay. Characterization of the algal strain was found to be Chlorella sorokiniana (MW769776). A single step affinity chromatographic technique was developed to purify Chlorella sorokiniana lectin (CSL) using guar gum as the affinity matrix. The precipitate showed a single active peak with a titer value of 1024 HU, with a concentration of 1111 U, and a purification fold of 9. The purified protein exhibited a single band in SDS-PAGE with a molecular weight of 16 kDa. Analysis by liquid chromatography-electrospray ionization-quadrupole-time of flight mass spectrometry (LC-ESI-Q-TOF-MS) of tryptic-digested purified lectin showed that it was a monomeric protein. A multiple sequence alignment analysis revealed that the peptide sequences of CSL exhibited similarity with the H-type lectin domain of Micractinium conductrix. The structure of CSL was studied by FTIR and homology modeling methods, indicating the presence of α-helix as well as β-sheet in its secondary structure. Whereas the 3D structure exhibited the similarity with the core protein of light-harvesting reaction center complex of photosystem I. The significance of this study suggests that the characteristics of CSL are consistent with its identification as a hemagglutinin, a type of novel lectin, which suggests its candidature for various biological purposes.Communicated by Ramaswamy H. Sarma.

Research advances and prospects of legume lectins

Lectins are widely distributed proteins having ability of binding selectively and reversibly with carbohydrates moieties and glycoconjugates. Although lectins have been reported from different biological sources, the legume lectins are the best-characterized family of plant lectins. Legume lectins are a large family of homologous proteins with considerable similarity in amino acid sequence and their tertiary structures. Despite having strong sequence conservation, these lectins show remarkable variability in carbohydrate specificity and quaternary structures. The ability of legume lectins in recognizing glycans and glycoconjugates on cells and other intracellular structures make them a valuable research tool in glycomic research. Due to variability in binding with glycans, glycoconjugates and multiple biological functions, legume lectins are the subject of intense research for their diverse application in different fields such as glycobiology, biomedical research and crop improvement. The present review specially focuses on structural and functional characteristics of legume lectins along with their potential areas of application.

Plant lectins and their many roles: Carbohydrate-binding and beyond

Lectins are ubiquitous proteins that reversibly bind to specific carbohydrates and, thus, serve as readers of the sugar code. In photosynthetic organisms, lectin family proteins play important roles in capturing and releasing photosynthates via an endogenous lectin cycle. Often, lectin proteins consist of one or more lectin domains in combination with other types of domains. This structural diversity of lectins is the basis for their current classification, which is consistent with their diverse functions in cell signaling associated with growth and development, as well as in the plant's response to biotic, symbiotic, and abiotic stimuli. Furthermore, the lectin family shows evolutionary expansion that has distinct clade-specific signatures. Although the function(s) of many plant lectin family genes are unknown, studies in the model plant Arabidopsis thaliana have provided insights into their diverse roles. Here, we have used a biocuration approach rooted in the critical review of scientific literature and information available in the public genomic databases to summarize the expression, localization, and known functions of lectins in Arabidopsis. A better understanding of the structure and function of lectins is expected to aid in improving agricultural productivity through the manipulation of candidate genes for breeding climate-resilient crops, or by regulating metabolic pathways by applications of plant growth regulators.

THE EFFECTIVENESS OF PHYTOLECTINS AND LECTIN COMPOSITIONS APPLICATION FOR SPRAYING PLANTS DURING VEGETATION

The effectiveness of the soybean plants spraying with the soybean seed lectin solution during vegetation (against the background of seed inoculation with nodule bacteria and without seed inoculation), as well as the effectiveness of the winter wheat plants spraying with lectin-bacterial composition in green-house and field experiments was investigated respectively. It was found that spraying of soybeans in the phase of two trifoliate leaves development with a specific lectin against the background of pre-sowing seed inoculation with rhizobia caused a significantly positive effect on the functional activity of the symbiotic apparatus. The nitrogen-fixing activity of the rhizosphere microbiota remained unchanged, which may indicate the vector of lectin action when sprayed through the plant. At the same time, the activation of plants vegetative growth was noted, which was maximally manifested by the height of their above ground part. The activity of exogenous sprayed lectin was less pronounced on the background of seed inoculation with rhizobia compared to non-inoculated plants. Plants spraying with soybean lectin against the background of seed inoculation provided an increase in harvest compared to non-inoculated control by 12.8 g/plant, but by the factor of lectin action this increase was only 1.15 g/plant and was insignificant. Non-inoculated soybean plants when sprayed with lectin formed a harvest that was significantly higher (by 3.86 g/plant) than that of plants in the absence of lectin. At this, the increase by the factor of lectin action was 22%. The spraying of winter wheat plants in the phase of mass spring germinations with the Azolec preparation (without pre-sowing seed inoculation) contributed to a significant increase in harvest by 1.6 c/ha. Therefore, the application of soybean and wheat plants spraying, respectively, with soybean seed lectin and lectin-bacterial Azolec preparation (wheat lectin),without involving pre-sowing seed inoculation, provided a greater degree of plants productive potential realization compared to control (without pre-sowing seed inoculation and plants spraying during vegetation).

Molecular Heterogeneity of Lectins in Wheat Seedlings under the Action of Stevioside and Heavy Metals

The effect of the diterpene glycoside stevioside and high concentrations of heavy metals on the molecular heterogeneity of lectins was studied in seedlings of Kazanskaya 560 winter wheat cultivar. Stevioside induced the emergence of a new 45-kDa lectin. Cultivation of wheat seedlings in CdSO₄ and ZnSO₄ solutions resulted in the emergence of the protein with Mr = 88 kDa. We detected the presence of both lectins in seedlings during combined treatment with stevioside and heavy metals.