“…While major β-(1,3)-glucan sources reside in fungal and bacterial cell walls (11)(12)(13), in plants, callose accumulates in specialized cells and interfaces including pollen tube walls (14), cell plates (2), sieve pores (15) and surrounding membranous intercellular channels named plasmodesmata (4,10,(16)(17)(18). Despite its low abundance, callose plays diverse and critical roles in plant development: forming protective papillae during pathogen attacks, controlling pollen development and thereby fertilization, and regulating cell-to-cell signalling and the transport of developmental proteins, RNAs and hormones via plasmodesmata (2,4,9,14,19,20). However, our knowledge of callose's physical properties, interactions with other cell wall components, and its overall impact on cell wall functions is limited (8,10).…”