Browsing by Author "Gray, William M"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Raw data for Xyloglucan deficiency leads to a reduction in turgor pressure and changes in cell wall properties affecting early seedling establishment
    (2024-04-08) Bou Daher, Firas; Serra, Leo; Carter, Ross; Jönsson, Henrik; Robinson, Sarah; Meyerowitz, Elliot M; Gray, William M; grayx051@umn.edu; Gray, William M; William Gray Lab
    Xyloglucan is believed to play a significant role in cell wall mechanics of dicot plants. Surprisingly, Arabidopsis plants defective in xyloglucan biosynthesis exhibit nearly normal growth and development. We investigated a mutant line, cslc-Δ5, lacking activity in all five Arabidopsis CSLC genes responsible for xyloglucan backbone biosynthesis. We observed that this xyloglucandeficient line exhibited reduced cellulose crystallinity and increased pectin levels, suggesting the existence of feedback mechanisms that regulate wall composition to compensate for the absence of xyloglucan. These alterations in cell wall composition in the xyloglucan-absent plants were further linked to a decrease in cell wall elasticity and rupture stress, as observed through atomic force microscopy and extensometer-based techniques. This raised questions about how plants with such modified cell wall properties can maintain normal growth. Our investigation revealed two key factors contributing to this phenomenon. Firstly, measurements of turgor pressure, a primary driver of plant growth, revealed that cslc-Δ5 plants have reduced turgor, preventing the compromised walls from bursting while still allowing growth to occur. Secondly, we discovered the conservation of elastic asymmetry (ratio of axial to transverse wall elasticity) in the mutant, suggesting an additional mechanism contributing to the maintenance of normal growth. This novel feedback mechanism between cell wall composition and mechanical properties, coupled with turgor pressure regulation, plays a central role in the control of plant growth and is critical for seedling establishment in a mechanically challenging environment by affecting shoot emergence and root penetration.
  • Thumbnail Image
    Item
    Raw data for: Biphasic Control of Cell Expansion by Auxin Coordinates Etiolated Seedling Development
    (2021-07-27) Du, Minmin; Bou Daher, Firas; Liu, Yuanyuan; Steward, Andrew; Tillman, Molly; Zhang, Xiaoyue; Wong, Jeh Haur; Ren, Hong; Cohen, Jerry D; Li, Chuanyou; Gray, William M; grayx051@umn.edu; Gray, William M; William Gray Lab
    Seedling emergence is critical for food security. It requires rapid hypocotyl elongation and apical hook formation, both of which are mediated by regulated cell expansion. How these events are coordinated in etiolated seedlings is unclear. Here, we show that biphasic control of cell expansion by the phytohormone auxin underlies this process. Shortly after germination, high auxin levels restrain elongation. This provides a temporal window for apical hook formation, involving a gravity-induced auxin maximum on the eventual concave side of the hook, triggering PP2C.D1-controlled asymmetrical H+-ATPase activity, resulting in differential cell elongation. Subsequently, auxin concentrations decline acropetally and switch from restraining to promoting elongation, driving hypocotyl elongation. Our findings elucidate how differential auxin concentrations throughout the hypocotyl coordinate etiolated development, leading to successful soil emergence.