Gallemí Marçal, Montesinos Juan Carlos, Zarevski Nikola, Pribyl Jan, Skládal Petr, Hannezo Edouard, Benková Eva
Develomental Biology Department, Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria.
Central European Institute of Technology (CEITEC-MU), Masaryk University, Brno, Czechia.
Front Plant Sci. 2025 Jul 4;16:1612366. doi: 10.3389/fpls.2025.1612366. eCollection 2025.
Acid-growth theory has been postulated in the 70s to explain the rapid elongation of plant cells in response to the hormone auxin. More recently, it has been demonstrated that activation of the proton ATPs pump (H-ATPs) promoting acidification of the apoplast is the principal mechanism by which auxin and other hormones such as brassinosteroids (BR) induce cell elongation. Despite these advances, the impact of this acidification on the mechanical properties of the cell wall remained largely unexplored.
Here, we use elongation assays of hypocotyls and Atomic Force Microscopy (AFM) to correlate hormone-induced tissue elongation and local changes in cell wall mechanical properties. Furthermore, employing transgenic lines over-expressing Pectin Methyl Esterase (PME), along with calcium chelators, we investigate the effect of pectin modification in hormone-driven cell elongation.
We demonstrate that acidification of apoplast is necessary and sufficient to induce cell elongation through promoting cell wall softening. Moreover, we show that enhanced PME activity can induce both cell wall softening or stiffening in extracellular calcium dependent-manner and that tight control of PME activity is required for proper hypocotyl elongation.
Our results confirm a dual role of PME in plant cell elongation. However, further investigation is needed to assess the status of pectin following short- or long-term PME treatments in order to determine if pectin methyl-esterification might promote its degradation as well as the role of PME inhibitors upon PME induction.
酸生长理论于20世纪70年代被提出，用以解释植物细胞对激素生长素的快速伸长反应。最近，研究表明促进质外体酸化的质子ATP酶（H-ATP）的激活是生长素和其他激素（如油菜素内酯，BR）诱导细胞伸长的主要机制。尽管取得了这些进展，但这种酸化对细胞壁力学性质的影响在很大程度上仍未得到探索。
在这里，我们使用下胚轴伸长测定法和原子力显微镜（AFM）来关联激素诱导的组织伸长和细胞壁力学性质的局部变化。此外，利用过表达果胶甲酯酶（PME）的转基因系以及钙螯合剂，我们研究了果胶修饰在激素驱动的细胞伸长中的作用。
我们证明质外体酸化通过促进细胞壁软化来诱导细胞伸长是必要且充分的。此外，我们表明增强的PME活性可以以细胞外钙依赖的方式诱导细胞壁软化或硬化，并且下胚轴的正常伸长需要对PME活性进行严格控制。
我们的结果证实了PME在植物细胞伸长中的双重作用。然而，需要进一步研究以评估短期或长期PME处理后果胶的状态，以确定果胶甲基酯化是否可能促进其降解以及PME抑制剂在PME诱导后的作用。
