Patterns of Cell Division, Cell Differentiation and Cell Elongation in Epidermis and Cortex of Arabidopsis pedicels in the Wild Type and in erecta

Abstract

Plant organ shape and size are established during growth by a predictable, controlled sequence of cell proliferation, differentiation, and elongation. To understand the regulation and coordination of these processes, we studied the temporal behavior of epidermal and cortex cells in Arabidopsis pedicels and used computational modeling to analyze cell behavior in tissues. Pedicels offer multiple advantages for such a study, as their growth is determinate, mostly one dimensional, and epidermis differentiation is uniform along the proximodistal axis. Three developmental stages were distinguished during pedicel growth: a proliferative stage, a stomata differentiation stage, and a cell elongation stage. Throughout the first two stages pedicel growth is exponential, while during the final stage growth becomes linear and depends on flower fertilization. During the first stage, the average cell cycle duration in the cortex and during symmetric divisions of epidermal cells was constant and cells divided at a fairly specific size. We also examined the mutant of ERECTA, a gene with strong influence on pedicel growth. We demonstrate that during the first two stages of pedicel development ERECTA is important for the rate of cell growth along the proximodistal axis and for cell cycle duration in epidermis and cortex. The second function of ERECTA is to prolong the proliferative phase and inhibit premature cell differentiation in the epidermis. Comparison of epidermis development in the wild type and erecta suggests that differentiation is a synchronized event in which the stomata differentiation and the transition of pavement cells from proliferation to expansion are intimately connected.

Vascular Cambium Development

“…ER has a general effect on inflorescence architecture; er loss-of-function mutants shoots have reduced size and compact stature (Torii et al, 1996;Bundy et al, 2012). Both ER and the closely related ERECTA-LIKE 1 (ERL1) are expressed in the phloem and xylem parenchyma tissue inside the vascular bundles of the inflorescence stem (Uchida and Tasaka, 2013).…”

Diverse Roles of ERECTA Family Genes in Plant Development

“…The mesophyll tissue of er leaves is made up of fewer cells that are more loosely packed (Masle et al ). A temporal study of pedicel development in wild type and the er mutant revealed that during early stages of organ growth ERECTA promotes elongation of epidermal and cortex cells along the proximodistal axis and thus impinges on the duration of cell cycle (Bundy et al ). At the same time, cell cycle progression in the er cortex is still coordinated with cell growth and the proliferative window is not affected, suggesting that ERECTA‐mediated signaling does not control the cortex cell cycle machinery (Bundy et al ).…”

“…A temporal study of pedicel development in wild type and the er mutant revealed that during early stages of organ growth ERECTA promotes elongation of epidermal and cortex cells along the proximodistal axis and thus impinges on the duration of cell cycle (Bundy et al ). At the same time, cell cycle progression in the er cortex is still coordinated with cell growth and the proliferative window is not affected, suggesting that ERECTA‐mediated signaling does not control the cortex cell cycle machinery (Bundy et al ). The regulation of cortex cell elongation is likely to be indirect, as expression of ERECTA in the phloem is sufficient to rescue cortical defects in the er mutant (Uchida et al ).…”

Endogenous hormonal equilibrium linked to bamboo culm development

“…In a growth curve analysis (total length vs time) of pedicels in A. thaliana, Bundy et al (2012) reported that growth is exponential for the first 16 days after which it becomes linear. However, the present study in bamboo found that cell lengths in culms increased in an essentially linear manner from initial to terminal stages ( Figure 3C).…”

“…Two factors determine the size of mature organs: cell number and cell size (Bundy et al, 2012). Plant hormones are natural compounds with the ability to affect physiological processes, particularly in the area of growth (Nemhauser et al, 2006), at concentrations far below those where either nutrients or vitamins can affect these processes (Davies, 2010).…”