Exploring the role of β-1,3-glucanase in aerenchyma development in sugarcane roots

Aerenchyma formation has emerged as a promising model for understanding cell wall modifications. Certain cells undergo programmed cell death, whereas others do not, suggesting the existence of a tightly regulated signalling dispersion mechanism. Cell-to-cell communication occurs via plasmodesmata, whose permeability is regulated by the deposition of callose (β-1,3-glucan) and its degradation by β-1,3-glucanase. These processes might be key to understanding the selection of specific cells, which modify their cell walls for aerenchyma formation. Therefore, the aim of this study was to characterize the role of callose and β-1,3-glucanase during aerenchyma formation.

Sugarcane roots were segmented into five sections, each 1 cm in length, and embedded in LR White resin. Semi-thin sections were obtained, and immunolocalization was performed using monoclonal antibodies for the polysaccharides callose (β-1,3-glucan) and mixed-linkage β-1,3-1,4-glucan. The protein for in situ localization was chosen based on its ontology and protein domain structure. A super-resolution microscope was used to identify the antibody signal deposition pattern.

The antibody signal against mixed-linkage β-1,3-1,4-glucan was detected continuously along the cell wall in the early root segments. Its removal and degradation became evident from the third segment onwards, coinciding with aerenchyma formation. In contrast, callose exhibited a punctate signal, possibly marking regions of plasmodesmata. Callose degradation followed a similar pattern to that of mixed-linkage β-1,3-1,4-glucan (segment 3-segment 5), although its signal was less abundant. The β-1,3-glucanase showed peak signal from segment 3 to segment 4, accompanied by a punctate signal, suggesting its action at regions of plasmodesmata and callose degradation sites.

The presence of callose raises critical questions about how cells transmit signals and why only certain cells undergo programmed cell death. Managing the permeability and selectivity of intercellular communication might be a key factor in various biological processes. Gaining insight into these mechanisms and identifying potential enzymes and polysaccharides could provide new perspectives for future research.