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.

Brassinosteroids Influence Arabidopsis Hypocotyl Graviresponses Through Changes In Mannans And Cellulose

“…Interestingly, our data are consistent with the fact that 528 gravistimulation of wild type Arabidopsis seedlings is accompanied by a strong 529 downregulation of one CSLA gene responsible for mannan biosynthesis (Millar and Kiss, 530 2013). Additionally, the level of galactoglucomannans was decreased by about 50% in 531 maize stem pulvini as a result of gravistimulation (Zhang et al, 2011). The negative 532 influence of mannans on shoot gravitropism is interesting from an evolutionary 533 perspective.…”

“…Mannans could interfere with the activities of xyloglucan 551 endotransglucosylase/hydrolases (XTHs) that seem to participate in the mechanism of 552 gravitropic bending (Zhang et al, 2011;Hu et al, 2013). XTHs were shown to use non-553 xyloglucan polysaccharides as donor substrates, although much less efficiently than 554 xyloglucans (Maris et al, 2011;Shinohara et al, 2017).…”

Spatial gradients in cell wall composition and transcriptional profiles along elongating maize internodes

“…The transcript levels of these genes increase substantially in the lower pulvini, where cell elongation is induced by gravitational stress [44]. The (1,3;1,4)-β-glucanase and the β-1,3-glucananase genes are also showed to be involved in gravitation-induced cell elongation in the lower region of maize pulvini [44].…”

Analysis of cellulose synthase genes from domesticated apple identifies collinear genes WDR53 and CesA8A: partial co-expression, bicistronic mRNA, and alternative splicing of CESA8A

“…The presence of a cell wall integrity (CWI) signalling pathway similar to that present in the yeast Saccharomyces cerevisiae (Levin, 2005) has been demonstrated in plants (Hématy et al ., 2009; Ringli, 2010; Hamann and Denness, 2011): the cell wall senses perturbations of its own structural and functional integrity, which is usually altered in situations of exogenous stresses (Steinwand and Kieber, 2010). Signalling cascades are then triggered, which activate hormone responses (Zhang et al ., 2011), ectopic lignin deposition (Caño-Delgado et al ., 2003; Denness et al ., 2011), and/or the synthesis of antimicrobial secondary metabolites (Hernández-Blanco et al ., 2007).…”