A Theoretical Model of Jigsaw-Puzzle Pattern Formation by Plant Leaf Epidermal Cells

Plant leaf epidermal cells exhibit a jigsaw puzzle–like pattern that is generated by interdigitation of the cell wall during leaf development. The contribution of two ROP GTPases, ROP2 and ROP6, to the cytoskeletal dynamics that regulate epidermal cell wall interdigitation has already been examined; however, how interactions between these molecules result in pattern formation remains to be elucidated. Here, we propose a simple interface equation model that incorporates both the cell wall remodeling activity of ROP GTPases and the diffusible signaling molecules by which they are regulated. This model successfully reproduces pattern formation observed in vivo, and explains the counterintuitive experimental results of decreased cellulose production and increased thickness. Our model also reproduces the dynamics of three-way cell wall junctions. Therefore, this model provides a possible mechanism for cell wall interdigitation formation in vivo.植物叶片表皮细胞呈现出类似拼图镶嵌的构型，该构型在叶片发育过程中由细胞壁的相互穿插嵌合所形成。已有研究对两类ROP小GTP酶（ROP GTPases）——ROP2与ROP6——在调控表皮细胞壁穿插嵌合的细胞骨架动力学中的作用进行了探讨；然而，这类分子间的相互作用如何促成该图案形成，仍有待阐明。本研究提出一款简易的界面方程模型，该模型同时整合了ROP小GTP酶的细胞壁重塑活性，以及调控其活性的可扩散信号分子。该模型成功复现了体内观测到的图案形成过程，并解释了纤维素合成减少、细胞壁厚度增加这一违背直觉的实验结果。本模型还复现了细胞壁三叉连接点的动态变化过程。因此，该模型为体内细胞壁穿插嵌合的形成机制提供了一种可行的解释路径。