| Abstract: | The ability of kappa (κ) and iota (ι) carrageenans to form gels is dependent upon the regular repeat of disaccharide units along the carbohydrate chain. Short, chemically- and enzymatically-purified fragments of κ and ι carrageenan were conjugated to fluorescein and used as specific hybridization probes for localization of κ and ι carrageenan gelling sequences within the cells walls and intercellular matrices of Kappaphycus alvarezii (Doty) Doty. The probes label cell walls and intercellular matrices under ionic conditions appropriate for gelation of κ and ι carrageenans. The distribution of κ and ι carrageenans in the matrix and cell walls of K. alvarezii was determined with respect to cell type (epidermis, cortex, medulla, and central axis) and age. The κ-probe labels the cell walls of all cell types except epidermal in both young and old tissues. In contrast, the ι-probe labels the cell walls of the epidermis in both young and old tissue and the cell walls of the thylles only in old tissue. Both probes label intercellular matrix material; however, ι-probe labelling is very much weaker than κ-probe labelling. The results indicate that FITC-conjugated carrageenan oligosaccharides are useful tools that provide information on gelling subunit distribution. |
