Abstract
Cellulose is an important component of cell wall, yet its location and function in pollen tubes remain speculative. In this paper, we studied the role of cellulose synthesis in pollen tube elongation in Pinus bungeana Zucc. by using the specific inhibitor, 2, 6-dichlorobenzonitrile (DCB). In the presence of DCB, the growth rate and morphology of pollen tubes were distinctly changed. The organization of cytoskeleton and vesicle trafficking were also disturbed. Ultrastructure of pollen tubes treated with DCB was characterized by the loose tube wall and damaged organelles. DCB treatment induced distinct changes in tube wall components. Fluorescence labeling results showed that callose, and acidic pectin accumulated in the tip regions, whereas there was less cellulose when treated with DCB. These results were confirmed by FTIR microspectroscopic analysis. In summary, our findings showed that inhibition of cellulose synthesis by DCB affected the organization of cytoskeleton and vesicle trafficking in pollen tubes, and induced changes in the tube wall chemical composition in a dose-dependent manner. These results confirm that cellulose is involved in the establishment of growth direction of pollen tubes, and plays important role in the cell wall construction during pollen tube development despite its lower quantity.
Highlights
Pollen tubes are cells that grow from their tips
Pollen tubes elongate by tip growth, whereas many other cells expand by diffuse growth, and the pollen tube attains its tubular shape via a polarized tipgrowth mechanism [7,39,40]
When DCB was added to the medium at the start of the culture period, the pollen grains were able to germinate at all DCB concentrations examined, with no significant differences in germination percentages among the DCB concentrations tested
Summary
Pollen tubes are cells that grow from their tips. Their elongation exhibits a polarized pattern of growth similar to that of fungal hyphae, root hairs and neuronal axon guidance in animals [1,2]. During the process of pollen tube growth, secretory vesicles derived from the Golgi apparatus transport large amounts of membrane and cell wall precursors to the tip [3,4]. Secretory vesicle membranes fuse with the plasma membrane, releasing the precursors and forming a new cell wall at the pollen tube tip, and pollen tube elongates [5,6,7]. The deposition and construction of angiosperm pollen tube wall have been extensively studied, our knowledge of the pollen tube wall of gymnosperms remain limited [17,18]
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