The primary beta-galactosidase BGAL10 modulates pavement cell shape acquisition in <i>Arabidopsis</i>

Cell shape acquisition is a fundamental biological process that allows cells to establish and maintain morphologies adapted to their specialised functions while preserving tissue integrity. In plants, this process is strongly influenced by the presence of the cell wall, a dynamic extracellular network of polysaccharides and proteins that surrounds the plasma membrane and physically connects neighbouring cells. By constraining and directing cellular expansion, the cell wall plays a central role in controlling cell shape. In Arabidopsis leaves, epidermal pavement cells adopt a characteristic jigsaw-puzzle-like morphology through the formation of interdigitating lobes and necks, providing a powerful model system for dissecting the mechanisms underlying complex plant cell shape acquisition. Here, we demonstrate the involvement of the glycoside hydrolase BETA-GALACTOSIDASE 10 (BGAL10) in pavement cell morphogenesis. Using high-resolution time-series imaging, we analysed cell growth dynamics alongside the spatial expression and subcellular localisation of BGAL10, revealing a prominent role for BGAL10 in mature cells, particularly at curved regions of the cell wall along pavement cell lobes. Furthermore, Brillouin microscopy revealed altered mechanical properties in the bgal10-1 mutant, most notably at lobe-indentation interfaces and cell junctions. Together, our results indicate that BGAL10 fine-tunes lobe outgrowth, likely through modification of the hemicellulose matrix, thereby regulating cell wall extensibility and mechanical stress distribution during pavement cell shape acquisition.