Laticifer growth pattern is guided by cytoskeleton organization

Abstract

Laticifers are secretory structures that produce latex, forming a specialized defense system against herbivory. Studies using anatomical approaches to investigate laticifer growth patterns have described their origin; however, their mode of growth, i.e., whether growth is intrusive or diffuse, remains unclear. Studies investigating how cytoskeleton filaments may influence laticifer shape establishment and growth patterns are lacking. In this study, we combined microtubule immunostaining and developmental anatomy to investigate the growth patterns in different types of laticifers. Standard anatomical methods were used to study laticifer development. Microtubules were labelled through immunolocalization of α-tubulin in three types of laticifers from three different plant species: nonanastomosing (Urvillea ulmacea), anastomosing unbranched with partial degradation of terminal cell walls (Ipomoea nil), and anastomosing branched laticifers with early and complete degradation of terminal cell walls (Asclepias curassavica). In both nonanastomosing and anastomosing laticifers, as well as in differentiating meristematic cells, parenchyma cells and idioblasts, microtubules were perpendicularly aligned to the cell growth axis. The analyses of laticifer microtubule orientation revealed an arrangement that corresponds to those cells that grow diffusely within the plant body. Nonanastomosing and anastomosing laticifers, branched or not, have a pattern which indicates diffuse growth. This innovative study on secretory structures represents a major advance in the knowledge of laticifers and their growth mode.

Development and Holocrine Secretion of Resin Ducts in Kielmeyera appariciana (Calophyllaceae)

“…In other cases, pectinase and cellulase activities were related to secretion release into the duct lumen, as described in Protium [26]. The participation of the cytoskeleton has never been identified during the splitting off of the epithelial cells, but its reorganization to promote diffuse or polarized growth is well-known in several cell types [23,27]. The cytoskeleton arrangement may also be involved in the secretory process, especially in granulocrine secretion, due to its coordination of vesicle trafficking within the cell during exocytosis [28].…”

“…The protocol of Medina et al [23] was used for microtubule labeling. Free-hand sections of shoot apices were fixed in PMET buffer (100 mM PIPES, 5 mM EGTA, 1 mM magnesium sulfate, pH 6.9) containing 0.5% glutaraldehyde, 1.5% formaldehyde fixative solution for 40 min.…”

“…Resin ducts of K. appariciana have been described as schizogenous, but there are no data on cellular changes related to the separation of cells or to the process of secretion release into the lumen [19]. Our knowledge of the action of enzymes and cytoskeleton in gland development and secretion release is still incipient, with studies carried out in ducts, glandular trichomes and laticifers of very few species [20][21][22][23]. In light of the scarcity of data and the many questions yet to be answered, the objective of this work was to analyze the development of the resin ducts of K. appariciana and the processes involved in the synthesis and release of the secretion.…”