title: Cell wall modifications in maize pulvini in response to gravitational stress.
abstract: Changes in cell wall polysaccharides, transcript abundance, metabolite profiles, and hormone concentrations were monitored in the upper and lower regions of maize (Zea mays) pulvini in response to gravistimulation, during which maize plants placed in a horizontal position returned to the vertical orientation. Heteroxylan levels increased in the lower regions of the pulvini, together with lignin, but xyloglucans and heteromannan contents decreased. The degree of substitution of heteroxylan with arabinofuranosyl residues decreased in the lower pulvini, which exhibited increased mechanical strength as the plants returned to the vertical position. Few or no changes in noncellulosic wall polysaccharides could be detected on the upper side of the pulvinus, and crystalline cellulose content remained essentially constant in both the upper and lower pulvinus. Microarray analyses showed that spatial and temporal changes in transcript profiles were consistent with the changes in wall composition that were observed in the lower regions of the pulvinus. In addition, the microarray analyses indicated that metabolic pathways leading to the biosynthesis of phytohormones were differentially activated in the upper and lower regions of the pulvinus in response to gravistimulation. Metabolite profiles and measured hormone concentrations were consistent with the microarray data, insofar as auxin, physiologically active gibberellic acid, and metabolites potentially involved in lignin biosynthesis increased in the elongating cells of the lower pulvinus.
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls and the Australian Centre for Plant Functional Genomics, Waite Research Institute, School of Agriculture, Food and Wine, University of Adelaide, South Australia 5064, Australia.
authors.forename: Qisen
authors.initials: Q
authors.lastname: Zhang
authors.forename: Filomena A
authors.initials: FA
authors.lastname: Pettolino
authors.forename: Kanwarpal S
authors.initials: KS
authors.lastname: Dhugga
authors.forename: J Antoni
authors.initials: JA
authors.lastname: Rafalski
authors.forename: Scott
authors.initials: S
authors.lastname: Tingey
authors.forename: Jillian
authors.initials: J
authors.lastname: Taylor
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Shirley
authors.forename: Kevin
authors.initials: K
authors.lastname: Hayes
authors.forename: Mary
authors.initials: M
authors.lastname: Beatty
authors.forename: Suzanne R
authors.initials: SR
authors.lastname: Abrams
authors.forename: L Irina
authors.initials: LI
authors.lastname: Zaharia
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Burton
authors.forename: Antony
authors.initials: A
authors.lastname: Bacic
authors.forename: Geoffrey B
authors.initials: GB
authors.lastname: Fincher
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D002473:Cell Wall / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism; D006112:Gravitation; D018522:Gravitropism; D008031:Lignin / Q000378:metabolism; D055432:Metabolomics; D008954:Models, Biological; D009711:Nucleotides / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010937:Plant Growth Regulators / Q000378:metabolism; D018547:Plant Stems / Q000502:physiology; D011134:Polysaccharides / Q000378:metabolism; D018516:Pulvinus / Q000166:cytology* / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological; D014158:Transcription, Genetic; D014990:Xylans / Q000378:metabolism; D003313:Zea mays / Q000166:cytology* / Q000201:enzymology / Q000235:genetics / Q000502:physiology*
chemical_list: D009711:Nucleotides; D010937:Plant Growth Regulators; D011134:Polysaccharides; D012333:RNA, Messenger; D014990:Xylans; D002482:Cellulose; D008031:Lignin; D016695:Glycosyltransferases