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.
Highlights
Cell proliferation and differentiation, including cell expansion, are crucial processes needed for organogenesis in multicellular organisms
Growth rate and final cell length are enhanced in tetraploid Arabidopsis seedlings To investigate the growth effects of increased ploidy in A. thaliana, we compared hypocotyl growth between diploid plants and tetraploid plants
This suggests that the promotion of hypocotyl elongation in tetraploid plants occurred as a result of a higher elongation rate in these plants compared to diploid plants (Fig 1E)
Summary
Cell proliferation and differentiation, including cell expansion, are crucial processes needed for organogenesis in multicellular organisms. Compared with animal tissues, organ growth in plants is more heavily dependent on cellular expansion. The size of the mature plant organ is largely determined by individual cell size. Cell size is regulated by a number of factors, including the timing of cell expansion onset, the cellular expansion rate, and the timing of expansion cessation. The regulatory mechanisms responsible for these processes have been investigated from two main perspectives. One perspective focuses on changes to the mechanical properties of the cell wall. These changes, which affect cellular water uptake, are regulated by environmental cues and plant hormones [2]. The other perspective focuses on PLOS ONE | DOI:10.1371/journal.pone.0134547 August 5, 2015
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