Manzano Concepcion, Morimoto Kevin W, Shaar-Moshe Lidor, Mason G Alex, Cantó-Pastor Alex, Gouran Mona, De Bellis Damien, Ursache Robertas, Kajala Kaisa, Sinha Neelima, Bailey-Serres Julia, Geldner Niko, Del Pozo J Carlos, Brady Siobhan M
Department of Plant Biology and Genome Center, University of California Davis, Davis, CA, USA.
Centro de Biotecnología y Genómica de Plantas (UPM-INIA/CSIC), Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria-CSIC (INIA/CSIC), Campus Montegancedo, Madrid, Spain.
Nat Plants. 2025 Jan;11(1):118-130. doi: 10.1038/s41477-024-01864-z. Epub 2024 Dec 2.
Multicellular organisms control environmental interactions through specialized barriers in specific cell types. A conserved barrier in plant roots is the endodermal Casparian strip (CS), a ring-like structure made of polymerized lignin that seals the endodermal apoplastic space. Most angiosperms have another root cell type, the exodermis, that is reported to form a barrier. Our understanding of exodermal developmental and molecular regulation and function is limited as this cell type is absent from Arabidopsis thaliana. We demonstrate that in tomato (Solanum lycopersicum), the exodermis does not form a CS. Instead, it forms a polar lignin cap (PLC) with equivalent barrier function to the endodermal CS but distinct genetic control. Repression of the exodermal PLC in inner cortical layers is conferred by the SlSCZ and SlEXO1 transcription factors, and these two factors genetically interact to control its polar deposition. Several target genes that act downstream of SlSCZ and SlEXO1 in the exodermis are identified. Although the exodermis and endodermis produce barriers that restrict mineral ion uptake, the exodermal PLC is unable to fully compensate for the lack of a CS. The presence of distinct lignin structures acting as apoplastic barriers has exciting implications for a root's response to abiotic and biotic stimuli.
多细胞生物通过特定细胞类型中的专门屏障来控制与环境的相互作用。植物根中的一种保守屏障是内皮层凯氏带（CS），它是由聚合木质素构成的环状结构，封闭了内皮层质外体空间。大多数被子植物还有另一种根细胞类型，即外皮层，据报道它能形成一种屏障。由于拟南芥中不存在这种细胞类型，我们对其发育、分子调控及功能的了解有限。我们证明，在番茄（Solanum lycopersicum）中，外皮层不形成凯氏带。相反，它形成了一个极性木质素帽（PLC），其屏障功能与内皮层凯氏带相当，但遗传控制不同。SlSCZ和SlEXO1转录因子可抑制内皮层中PLC在外皮层的形成，这两个因子通过遗传相互作用来控制其极性沉积。我们还鉴定了在外皮层中位于SlSCZ和SlEXO1下游起作用的几个靶基因。虽然外皮层和内皮层都会产生限制矿质离子吸收的屏障，但外皮层的PLC无法完全弥补凯氏带的缺失。不同的木质素结构作为质外体屏障的存在，对根对非生物和生物刺激的反应具有令人兴奋的意义。
