Research Highlights

Plant lectins: Sugar sensing for pollen development

Arabidopsis thaliana wild type plant. © 2008 Nature Publishing Group

Plant — predominantly legume — lectins are frequently used tools in glycobiology research. Plants are also known to have lectin receptor-like kinases (RLKs), a large family of receptor-like kinases with an extracellular legume lectin-like domain. Little is known about lectin RLKs, and now Wan et al., reporting to Plant Molecular Biology, show that the lectin RLK encoded by the gene At3g53810 — named SGC lectin RLK — is required for pollen development in Arabidopsis thaliana.

Gene function in plants can be analyzed by insertion of a portion of the Agrobacterium tumefaciens tumor-inducing plasmid into the genome, a technique called T-DNA insertion. The authors observed that male T-DNA insertion mutants of the analyzed lectin RLK were sterile, however, the pollen release from the anthers was not disrupted. Instead, Wan et al. found that male infertility was caused by pollen grains that were deformed and smaller than their wild-type counterparts. As the mutant pollen grains also stuck to the inside wall of the anther, Wan et al. named the A. thaliana mutant sgc — small, glued-together and collapsed pollen. These findings indicated that the SGC Lectin RLK has an important role in pollen development.

Although some RLKs have been shown to regulate pollen development in A. thaliana, none of them possesses a lectin-like domain. Wan et al. point out that due to the domain's amino acid composition, the SGC Lectin RLK more likely binds oligosaccharides rather than monosaccharides. Free oligosaccharides such as oligoglucans or oligogalacturonic acids occur during pollen development when the tetrad callose walls or pectin are degraded. Thus, such oligosaccharides may bind to the SGC Lectin RLK and initiate intracellular signaling events that regulate pollen development.

Author: Mirko von Elstermann