Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN 55108, USA; Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK.
Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK.
Curr Biol. 2024 May 20;34(10):2094-2106.e6. doi: 10.1016/j.cub.2024.04.016. Epub 2024 Apr 26.
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 cellulose synthase like-C (CSLC) genes responsible for xyloglucan backbone biosynthesis. We observed that this xyloglucan-deficient 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 elastic modulus and rupture stress, as observed through atomic force microscopy (AFM) 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. First, 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. Second, 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.
木葡聚糖被认为在双子叶植物细胞壁力学中起着重要作用。令人惊讶的是，木葡聚糖生物合成缺陷的拟南芥植物表现出几乎正常的生长和发育。我们研究了一个突变体系 cslc-Δ5，该突变体系缺乏负责木葡聚糖骨架生物合成的五个拟南芥纤维素合酶样-C（CSLC）基因的全部活性。我们观察到，这个木葡聚糖缺乏的品系表现出纤维素结晶度降低和果胶水平升高，这表明存在反馈机制，可调节细胞壁组成以补偿木葡聚糖的缺失。木葡聚糖缺失植物细胞壁组成的这些变化与细胞壁弹性模量和破裂应力的降低进一步相关，这可以通过原子力显微镜（AFM）和基于拉伸计的技术观察到。这就提出了一个问题，即细胞壁特性如此改变的植物如何能够维持正常生长。我们的研究揭示了两个导致这种现象的关键因素。首先，对膨压（植物生长的主要驱动力）的测量表明，cslc-Δ5 植物的膨压低，防止受损的细胞壁破裂，同时仍允许生长发生。其次，我们发现突变体中弹性不对称性（轴向与横向细胞壁弹性的比值）的保守性，这表明存在另一种机制有助于维持正常生长。细胞壁组成和机械性能之间的这种新的反馈机制，加上膨压调节，在控制植物生长中起着核心作用，并且通过影响芽鞘萌发和根穿透，对在机械挑战性环境中幼苗的建立至关重要。
