Premium
A distinct class of vesicles derived from the trans ‐Golgi mediates secretion of xylogalacturonan in the root border cell
Author(s) -
Wang Pengfei,
Chen Xinshi,
Goldbeck Cameron,
Chung Eric,
Kang ByungHo
Publication year - 2017
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13704
Subject(s) - golgi apparatus , vesicle , secretion , microbiology and biotechnology , epitope , cytoplasm , secretory vesicle , cell plate , secretory pathway , biology , chemistry , biochemistry , cell , endoplasmic reticulum , membrane , antigen , cell division , immunology , cytokinesis
Summary Root border cells lie on the surface of the root cap and secrete massive amounts of mucilage that contains polysaccharides and proteoglycans. Golgi stacks in the border cells have hypertrophied margins, reflecting elevated biosynthetic activity to produce the polysaccharide components of the mucilage. To investigate the three‐dimensional structures and macromolecular compositions of these Golgi stacks, we examined high‐pressure frozen/freeze‐substituted alfalfa root cap cells with electron microscopy/tomography. Golgi stacks in border cells and peripheral cells, precursor cells of border cells, displayed similar morphological features, such as proliferation of trans cisternae and swelling of the trans cisternae and trans ‐Golgi network ( TGN ) compartments. These swollen margins give rise to two types of vesicles larger than other Golgi‐associated vesicles. Margins of trans ‐Golgi cisternae accumulate the LM 8 xylogalacturonan ( XGA ) epitope, and they become darkly stained large vesicles ( LV s) after release from the Golgi. Epitopes for xyloglucan ( XG ), polygalacturonic acid/rhamnogalacturonan‐I ( PGA / RG ‐I) are detected in the trans ‐most cisternae and TGN compartments. LV s produced from TGN compartments ( TGN ‐ LV s) stained lighter than LV s and contained the cell wall polysaccharide epitopes seen in the TGN . LV s carrying the XGA epitope fuse with the plasma membrane only in border cells, whereas TGN ‐ LV s containing the XG and PGA / RG ‐I epitopes fuse with the plasma membrane of both peripheral cells and border cells. Taken together, these results indicate that XGA is secreted by a novel type of secretory vesicles derived from trans ‐Golgi cisternae. Furthermore, we simulated the collapse in the central domain of the trans ‐cisternae accompanying polysaccharide synthesis with a mathematical model.