Polysaccharide compositions of collenchyma cell walls from celery (Apium graveolens L.) petioles

• Published in: BMC plant biology 2017-06, Vol.17 (1), p.104-104, Article 104
• Main Authors: Chen, Da, Harris, Philip J, Sims, Ian M, Zujovic, Zoran, Melton, Laurence D
• Format: Article
• Language: English
• Subjects: Anatomy; Antimicrobial Cationic Peptides; Apium graveolens - chemistry; Apium graveolens - cytology; Apium graveolens - growth & development; Celery; Cell Wall - chemistry; Cell walls; Cellulose; Chemical analysis; Chemical composition; Collenchyma; Cross polarization; Elongation; Esterification; Excitation spectra; Genetic aspects; Glycosylation; Ground tissues; Hemicelluloses; Linkage analysis; Magnetic resonance spectroscopy; Microscopy; Monosaccharides - analysis; NMR; NMR spectroscopy; Nuclear magnetic resonance; Parenchyma; Pectin; Plant cell walls; Plant Cells - chemistry; Plant Proteins; Plant Stems - chemistry; Polarization; Polysaccharides; Polysaccharides - analysis; Properties; Rhamnogalacturonan; Saccharides; Segments; Strands; Walls; Xyloglucan
• ISSN: 1471-2229; 1471-2229
• DOI: 10.1186/s12870-017-1046-y

Collenchyma serves as a mechanical support tissue for many herbaceous plants. Previous work based on solid-state NMR and immunomicroscopy suggested collenchyma cell walls (CWs) may have similar polysaccharide compositions to those commonly found in eudicotyledon parenchyma walls, but no detailed chemical analysis was available. In this study, compositions and structures of cell wall polysaccharides of peripheral collenchyma from celery petioles were investigated. This is the first detailed investigation of the cell wall composition of collenchyma from any plant. Celery petioles were found to elongate throughout their length during early growth, but as they matured elongation was increasingly confined to the upper region, until elongation ceased. Mature, fully elongated, petioles were divided into three equal segments, upper, middle and lower, and peripheral collenchyma strands isolated from each. Cell walls (CWs) were prepared from the strands, which also yielded a HEPES buffer soluble fraction. The CWs were sequentially extracted with CDTA, Na CO , 1 M KOH and 4 M KOH. Monosaccharide compositions of the CWs showed that pectin was the most abundant polysaccharide [with homogalacturonan (HG) more abundant than rhamnogalacturonan I (RG-I) and rhamnogalacturonan II (RG-II)], followed by cellulose, and other polysaccharides, mainly xyloglucans, with smaller amounts of heteroxylans and heteromannans. CWs from different segments had similar compositions, but those from the upper segments had slightly more pectin than those from the lower two segments. Further, the pectin in the CWs of the upper segment had a higher degree of methyl esterification than the other segments. In addition to the anticipated water-soluble pectins, the HEPES-soluble fractions surprisingly contained large amounts of heteroxylans. The CDTA and Na CO fractions were rich in HG and RG-I, the 1 M KOH fraction had abundant heteroxylans, the 4 M KOH fraction was rich in xyloglucan and heteromannans, and cellulose was predominant in the final residue. The structures of the xyloglucans, heteroxylans and heteromannans were deduced from the linkage analysis and were similar to those present in most eudicotyledon parenchyma CWs. Cross polarization with magic angle spinning (CP/MAS) NMR spectroscopy showed no apparent difference in the rigid and semi-rigid polysaccharides in the CWs of the three segments. Single-pulse excitation with magic-angle spinning (SPE/MAS) NMR spectroscopy, which detects high