Stimulation of Cell Elongation by Tetraploidy in Hypocotyls of Dark-Grown Arabidopsis Seedlings

Abstract

Plant size is largely determined by the size of individual cells. A number of studies showed a link between ploidy and cell size in land plants, but this link remains controversial. In this study, post-germination growth, which occurs entirely by cell elongation, was examined in diploid and autotetraploid hypocotyls of Arabidopsis thaliana (L.) Heynh. Final hypocotyl length was longer in tetraploid plants than in diploid plants, particularly when seedlings were grown in the dark. The longer hypocotyl in the tetraploid seedlings developed as a result of enhanced cell elongation rather than by an increase in cell number. DNA microarray analysis showed that genes involved in the transport of cuticle precursors were downregulated in a defined region of the tetraploid hypocotyl when compared to the diploid hypocotyl. Cuticle permeability, as assessed by toluidine-blue staining, and cuticular structure, as visualized by electron microscopy, were altered in tetraploid plants. Taken together, these data indicate that promotion of cell elongation is responsible for ploidy-dependent size determination in the Arabidopsis hypocotyl, and that this process is directly or indirectly related to cuticular function.

MYB30 links ROS signaling, root cell elongation, and plant immune responses

“…This is in line with a known function of the regulator MYB30, which has been reported to be a transcriptional activator for VLCFA metabolism genes in the leaf (23). Importantly, the cuticule has been implicated in cell elongation and plant growth (28). However, root cells of Arabidopsis do not accumulate cuticular wax on their surface.…”

Ploidy and Size at Multiple Scales in the Arabidopsis Sepal

“…For example, genes involved in hormone signaling (Yu et al, 2010;Zhao et al, 2017) and stress response (Lu et al, 2006;Yu et al, 2010;Kim and Chen, 2011;del Pozo and Ramirez-Parra, 2014) tend to be upregulated in diverse autopolyploids. Many transcriptional responses to autopolyploidy appear to represent adjustments to increased cell size; cell surface and cell wall proteins are differentially expressed in polyploid lineages of yeast and Arabidopsis (Wu et al, 2010;Yu et al, 2010;Narukawa et al, 2015). Thus, transcriptional responses to WGM may reflect a cell sizesensing mechanism (Wu et al, 2010) and may provide valuable insights into how such size sensing is achieved.…”

Possible pathways linking ploidy level to cell elongation and cuticular function in hypocotyls of dark-grown Arabidopsis seedlings

“…This developmental process is entirely governed by cell elongation, in both diploid and colchicine-induced tetraploid seedlings. 6 Final hypocotyl length was longer by 19% in tetraploid than in diploid as a result of additional stimulation of cell elongation in the tetraploid plants. The difference in hypocotyl length was particularly apparent in darkgrown seedlings.…”

“…Some of these genes encoded lipid transfer proteins (LTPs), which were proposed as carriers of cuticular lipids or as lipid-derived signaling molecules. 7 Cuticle permeability, as determined using toluidine blue (TB), a hydrophilic dye that only penetrates impaired cuticle, 8 was higher in tetraploid plants than in diploid plants 6 : In the tetraploid, the hypocotyl is stained by TB more broadly than in diploid plants, from the apical down the middle part of the hypocotyl. Cuticular structure was also disorganized and diffused in tetraploid plants, as visualized using transmission electron microscopy (TEM).…”

“…Previously, we suggested that cell elongation and cuticular function might be functionally linked during ploidy-dependent cell size elevation in Arabidopsis hypocotyls. 6 We proposed 2 possible models to explain the putative pathways. The first model envisages that the cuticle functions as a load-bearing surface that mechanically constrains cell wall expansion and hence controls expansion growth of the whole hypocotyl.…”