A role for pectin de‐methylesterification in a developmentally regulated growth acceleration in dark‐grown Arabidopsis hypocotyls

Abstract

Summary We focused on a developmentally regulated growth acceleration in the dark‐grown Arabidopsis hypocotyl to study the role of changes in cell wall metabolism in the control of cell elongation. To this end, precise transcriptome analysis on dissected dark‐grown hypocotyls, Fourier transform infrared (FT‐IR) microspectroscopy and kinematic analysis were used. Using a cellulose synthesis inhibitor, we showed that the growth acceleration marks a developmental transition during which growth becomes uncoupled from cellulose synthesis. We next investigated the cellular changes that take place during this transition. FT‐IR microspectroscopy revealed significant changes in cell wall composition during, but not after, the growth acceleration. Transcriptome analysis suggested a role for cell wall remodeling, in particular pectin modification, in this growth acceleration. This was confirmed by the overexpression of a pectin methylesterase inhibitor, which caused a delay in the growth acceleration. This study shows that the acceleration of cell elongation marks a developmental transition in dark‐grown hypocotyl cells and supports a role for pectin de‐methylesterification in the timing of this event.

Demethylesterification of Cell Wall Pectins in Arabidopsis Plays a Role in Seed Germination

“…through PME inhibition) could lead to either enhanced or reduced elongation growth, implying an increased or decreased wall extensibility, respectively. For example, reduced elongation is the case for the growth of hypocotyls and pollen tubes (Bosch and Hepler, 2005;Derbyshire et al, 2007;Pelletier et al, 2010). As far as germination is concerned, in this study, the overexpressing PMEI lines exhibited a higher degree of cell wall pectin methylesterification, and the seeds completed germination faster.…”

“…PMEI1 and PMEI2 (Wolf et al, 2003) are highly expressed in flowers; PMEI1 expression is specific to pollen, while the expression of PMEI3 is particularly high in the apical meristem (Peaucelle et al, 2008). PMEI4 is up-regulated during growth acceleration in skotomorphic hypocotyls (Pelletier et al, 2010). PMEI5 is not represented on the most commonly used microarray chips; thus, no prior information was available about its expression patterns.…”

“…S3) are likely indicative of this inhibitor interacting with a number of different PMEs, similar to the findings of others in which PMEIs show cross-species and even cross-family interactions . Pelletier et al (2010) overexpressed the PMEI3 gene in Arabidopsis to study the role of pectin methylesterification in dark-induced hypocotyl elongation. Interestingly, they did not observe several of the morphological phenotypes evident in our PMEI5 OE line, including the looping stem growth (Supplemental Fig.…”

“…S1) supported the view that these activity changes affect the degree of pectin methylesterification. The samples were separated based on principal component 1, whose loading was strong in the region associated with ester bonds (Derbyshire et al, 2007;Pelletier et al, 2010).…”

Neighbor Detection Induces Organ-Specific Transcriptomes, Revealing Patterns Underlying Hypocotyl-Specific Growth

“…To test whether the gene expression signature observed in rapidly growing shade-treated hypocotyls is also observed in other situations leading to hypocotyl elongation, we compared our data with gene expression patterns in rapidly elongating etiolated hypocotyls (Pelletier et al, 2010). In this study, gene expression was compared among hypocotyls at 45 to 48 h, 48 to 52 h, and 52 to 55 h postgermination, with rapid hypocotyl elongation starting after 48 h (Pelletier et al, 2010).…”