Plant cell growth requires the coordinated expansion of the protoplast and the cell wall, which is controlled by an elaborate system of cell wall integrity (CWI) sensors linking the different cellular compartments. LRR-eXtensins (LRXs) are cell wall-attached extracellular regulators of cell wall formation and high-affinity binding sites for RALF (Rapid ALkalinization Factor) peptide hormones that trigger diverse physiological processes related to cell growth. LRXs function in CWI sensing and in the case of LRX4 of Arabidopsis thaliana, this activity was shown to involve interaction with the transmembrane Catharanthus roseus Receptor-Like Kinase1-Like (CrRLK1L) protein FERONIA (FER). Here, we demonstrate that binding of RALF1 and FER is common to most tested LRXs of vegetative tissue, including LRX1, the main LRX protein of root hairs. Consequently, an lrx1-lrx5 quintuple mutant line develops shoot and root phenotypes reminiscent of the fer-4 knock-out mutant. The previously observed membrane-association of LRXs, however, is FER-independent, suggesting that LRXs bind not only FER but also other membrane-localized proteins to establish a physical link between intra- and extracellular compartments. Despite evolutionary diversification of various LRX proteins, overexpression of several chimeric LRX constructs causes cross-complementation of lrx mutants, indicative of comparable functions among members of this protein family. Suppressors of the pollen-growth defects induced by mutations in the CrRLK1Ls ANXUR1/2 also alleviate lrx1 lrx2-induced mutant root hair phenotypes. This suggests functional similarity of LRX-CrRLK1L signaling processes in very different cell types and indicates that LRX proteins are components of conserved processes regulating cell growth.

植物细胞的生长需要原生质体和细胞壁的协调膨胀，这由连接不同细胞区室的精细细胞壁完整性（CWI）传感器系统控制。LR R-e X肌腱蛋白（LRXs）是细胞壁附着的细胞壁形成细胞外调节剂，并且是RALF（R apid AL kalinization F actor）肽激素的高亲和力结合位点，可触发与细胞生长相关的各种生理过程。在CWI感测和在LRX4的情况下LRXs功能拟南芥，此活性显示与跨膜涉及相互作用Ç atharanthus ř oseus ř eceptor-大号IKE ķ inase 1 -大号IKE（CrRLK1L）蛋白FER ONIA（FER）。在这里，我们证明了RALF1和FER的结合对于大多数经过测试的营养组织LRX（包括根毛的主要LRX蛋白LRX1）都是常见的。因此，一个lrx1 - lrx5五倍体突变株形成芽和根表型，使人联想到fer-4敲除突变体。然而，先前观察到的LRX的膜缔合是与FER无关的，这表明LRX不仅结合FER，而且还结合其他膜定位的蛋白，从而在细胞内和细胞外区室之间建立了物理联系。尽管各种LRX蛋白在进化上多样化，但几种嵌合LRX构建体的过表达导致lrx突变体的交叉互补，表明该蛋白家族成员之间具有可比的功能。CrRLK1Ls ANXUR1 / 2突变引起的花粉生长缺陷抑制因子也减轻了lrx1 lrx2-诱导的突变根毛表型。这表明在非常不同的细胞类型中LRX-CrRLK1L信号传导过程的功能相似性，并表明LRX蛋白是调节细胞生长的保守过程的组成部分。