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Callose, a linear (1,3)-β-glucan, is an indispensable carbohydrate polymer required for plant growth and development. Advances in biochemical, genetic, and genomic tools, along with specific antibodies, have significantly enhanced our understanding of callose biosynthesis. As additional components of the callose synthase machinery emerge, the elucidation of molecular biosynthetic mechanisms is expected to follow. Short-term objectives involve defining the stoichiometry and turnover rates of callose synthase subunits. Long-term goals include generating recombinant callose synthases to elucidate their biochemical properties and molecular mechanisms, potentially culminating in the determination of callose synthase three-dimensional structure. This review delves into the structures and intricate molecular processes underlying callose biosynthesis, emphasizing regulatory elements and assembly mechanisms. [Display omitted] • Highlighting the critical role of callose biosynthesis in plant growth and defense. • Reviewing the composition of callose synthase complexes and the current understanding of callose assembly mechanisms. • Exploring genes encoding callose synthase and regulatory elements across various plant developmental stages. [ABSTRACT FROM AUTHOR]

Abiotic stress affects plants' growth and development. Soybean is an important crop of the world, however, its production is affected by abiotic stresses. Callose Synthase is the most crucial enzyme response to environmental and developmental signals. However, in soybean, information on the callose synthase genes is limited. In this study, we analyzed the callose synthase gene family of soybean at the genome-wide scale. We also studied the genes positions, gene structure, evolutionary relations, miRNAs target sites, and expression of CalS genes. Resultantly 24 CalS genes were found in soybean, with diverse chromosomal locations, cis -acting elements, conserved motifs, and gene structures. Further, GmCalS genes were divided into four phylogenetic classes. The evolutionary classification of CalSs was supported by the motif and gene structure analyses. Phytohormones, abiotic stresses, and growth-responsive elements were identified in the promoter of GmCalSs. In addition, the GmCalS genes higher expression in roots, leaves, flowers, and nodules tissues provided their significance in development. Furthermore, the higher expression of GmCalS17 and GmCalS19 genes in response to salt stress indicated their importance against salt stress. These findings will be helpful for further investigation of the CalS genes in other crops. [ABSTRACT FROM AUTHOR]

Abstract: Callose is the major polysaccharide present in the callose wall of developing microspores and the growing pollen tube wall. It is also an essential component of other specialized cell walls and its synthesis can be induced by pathogen infection, wounding and environmental cues. Among the 12 callose synthase genes (CalS) present in the Arabidopsis genome, CalS5 plays the predominant role in the synthesis of the callose wall, callose plugs and pollen tube wall. When expressed as a GFP-tagged protein in cultured tobacco BY-2 cells, CalS5 was found to be present in the plasma membrane and the Golgi-related endomembranes. Unlike the cell plate-specific CalS1 isozyme, CalS5 was not concentrated to the cell plate at cytokinesis. Expression of CalS5 resulted in callose accumulation only in the cell wall of BY-2 cells. The fact that no callose was found in the endomembranes suggests that CalS5 is not functional in that compartment. These cells exhibited a decreased plasmolysis rate in hypotonic solutions and an increased cytolysis rate in hypertonic conditions. This study demonstrates that an artificial callose wall could be synthesized by expressing a callose synthase enzyme. [Copyright &y& Elsevier]

Summary: Callose or β-1,3-glucan performs multiple functions during male and female gametophyte development. Callose is synthesized by 12 members of the glucan synthase-like (GSL) gene family in Arabidopsis thaliana. To elucidate the biological roles of Arabidopsis GSL family members during sexual development, we initiated a reverse genetic approach with T-DNA insertional mutagenesis lines. We screened T-DNA insertion lines for all members of the GSL gene family and detected homozygous mutant seedlings for all members except GSL10. Three independent alleles in GSL10, gsl10-1, gsl10-3 and gsl10-4 showed distorted segregation (1:1:0) of T-DNA inserts rather than Mendelian segregation (1:2:1). By genetic analysis through reciprocal cross, we determined that gsl10 pollen could not be transmitted to descendent. The mutant pollen of GSL10/gsl10 plants at tetrad and microspore stages were not different from that of wild type, suggesting that GSL10 is not essential for normal microspore growth. Analysis of GSL10/gsl10 hemizygous pollen during development revealed abnormal function in asymmetric microspore division. gsl10 mutant microspores failed to enter into mitosis. Unlike the previously described functions of GSL1, GSL2 and GSL5, GSL10 involves an independent process of pollen development at the mitotic division stage. [Copyright &y& Elsevier]

Abstract: Callose ((1,3)-β-glucan) is important during basic developmental processes of plants, but only little is known about the regulation of callose biosynthesis on molecular level. Growing evidence indicates that glucan synthase-like (GSL) genes in higher plants are involved in callose synthesis. We analyzed the expression of eight GSL genes (TaGSL) as well as callose synthase activity and total callose content in the stem, leaf blade and spike of wheat (Triticum aestivum L.). Organ-specific expression of six TaGSL genes and strong differences in expression levels were detected by quantitative real-time PCR. Differences were also determined in callose synthase (EC 2.4.1.34) activity and total amount of callose in the examined organs. Aniline blue staining in tissue sections localized callose depositions. These results allow a comprehensive reflection of callose regulation, considering gene expression, enzyme activity and enzyme product quantification as well as localization. Our data suggests that callose synthesis is highly regulated by a combination of GSL genes, which are involved either in general or in organ-specific developmental processes. [Copyright &y& Elsevier]