Spatial gradients in cell wall composition and transcriptional profiles along elongating maize internodes
1 Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide, 5064 Adelaide, South Australia, Australia
2 Australian Research Council Centre of Excellence in Plant Cell Walls, School of Botany, University of Melbourne, 3010 Parkville, Victoria, Australia
3 Genetic Discovery Group, Crop Genetics Research and Development, Pioneer Hi-Bred International Inc. 7300 NW 62nd Avenue, 50131-1004 Johnston, IA, USA
4 Genetic Discovery Group, DuPont Crop Genetics Research, DuPont Experimental Station, Building E353, 198803 Wilmington, DE, USA
BMC Plant Biology 2014, 14:27 doi:10.1186/1471-2229-14-27Published: 14 January 2014
The elongating maize internode represents a useful system for following development of cell walls in vegetative cells in the Poaceae family. Elongating internodes can be divided into four developmental zones, namely the basal intercalary meristem, above which are found the elongation, transition and maturation zones. Cells in the basal meristem and elongation zones contain mainly primary walls, while secondary cell wall deposition accelerates in the transition zone and predominates in the maturation zone.
The major wall components cellulose, lignin and glucuronoarabinoxylan (GAX) increased without any abrupt changes across the elongation, transition and maturation zones, although GAX appeared to increase more between the elongation and transition zones. Microarray analyses show that transcript abundance of key glycosyl transferase genes known to be involved in wall synthesis or re-modelling did not match the increases in cellulose, GAX and lignin. Rather, transcript levels of many of these genes were low in the meristematic and elongation zones, quickly increased to maximal levels in the transition zone and lower sections of the maturation zone, and generally decreased in the upper maturation zone sections. Genes with transcript profiles showing this pattern included secondary cell wall CesA genes, GT43 genes, some β-expansins, UDP-Xylose synthase and UDP-Glucose pyrophosphorylase, some xyloglucan endotransglycosylases/hydrolases, genes involved in monolignol biosynthesis, and NAM and MYB transcription factor genes.
The data indicated that the enzymic products of genes involved in cell wall synthesis and modification remain active right along the maturation zone of elongating maize internodes, despite the fact that corresponding transcript levels peak earlier, near or in the transition zone.