23 24 Short title: SUB mediates cell wall stress signaling 25 26 Abstract 29 Plant cells are encased in a semi-rigid cell wall of complex build. As a consequence, 30 cell wall remodeling is essential for the control of growth and development as well as 31 the regulation of abiotic and biotic stress responses. Plant cells actively sense physico-32 chemical changes in the cell wall and initiate corresponding cellular responses. 33 However, the underlying cell wall monitoring mechanisms remain poorly understood.34 In Arabidopsis the atypical receptor kinase STRUBBELIG (SUB) mediates tissue 35 morphogenesis. Here, we show that SUB-mediated signal transduction also regulates 36 the cellular response to a reduction in the biosynthesis of cellulose, a central 37 carbohydrate component of the cell wall. SUB signaling affects early increase of 38 intracellular reactive oxygen species, stress gene induction as well as ectopic lignin 39 and callose accumulation upon exogenous application of the cellulose biosynthesis 40 inhibitor isoxaben. Moreover, our data reveal that SUB signaling is required for 41 maintaining cell size and shape of root epidermal cells and the recovery of root 42 growth after transient exposure to isoxaben. SUB is also required for root growth 43 arrest in mutants with defective cellulose biosynthesis. Genetic data further indicate 44 that SUB controls the isoxaben-induced cell wall stress response independently from 45 other known receptor kinase genes mediating this response, such as THESEUS1 or 46 MIK2. We propose that SUB functions in a least two distinct biological processes: the 47 control of tissue morphogenesis and the response to cell wall damage. Taken together, 48 our results reveal a novel signal transduction pathway that contributes to the 49 molecular framework underlying cell wall integrity signaling. 50 51 52 3 53 Author Summary54 Plant cells are encapsulated by a semi-rigid and biochemically complex cell wall. This 55 particular feature has consequences for multiple biologically important processes, 56 such as cell and organ growth or various stress responses. For a plant cell to grow the 57 cell wall has to be modified to allow cell expansion, which is driven by outward-58 directed turgor pressure generated inside the cell. In return, changes in cell wall 59 architecture need to be monitored by individual cells, and to be coordinated across 60 cells in a growing tissue, for an organ to attain its regular size and shape. Cell wall 61 surveillance also comes also into play in the reaction against certain stresses, 62 including for example infection by plant pathogens, many of which break through the 63 cell wall during infection, thereby generating wall-derived factors that can induce 64 defense responses. There is only limited knowledge regarding the molecular system 65 that monitors the composition and status of the cell wall. Here we provide further 66 insight into the mechanism. We show that the cell surface receptor STRUBBELIG, 67 previously known to control organ development in Ar...

Combination of calcium and potassium (Ca-K) influences cadmium and zinc uptake and translocation in dwarf Polish wheat (Triticum polonicum), but its effects remain unclear. In the present study, a high concentration of Ca-K reduced uptake of Cd and Zn by roots and promoted their translocations to shoots under Cd and Zn excess. Whatever under a low or high concentration of Ca-K, Zn inhibited Cd uptake and translocation under Cd+Zn stress when compared with Cd stress alone. However, the reduced Cd content caused by Zn under the high concentration of Ca-K was significantly lower than under the low concentration of Ca-K. Under both Ca-K treatments, Cd promoted Zn uptake and inhibited Zn translocation under Cd+Zn stress when compared with those under Zn stress. The high concentration of Ca-K reinforced the promotion of Zn uptake and the inhibition of Zn translocation caused by Cd. The Ca-K or Zn affected the expression of several metal transporters and influenced cell wall metabolism, the subcellular distribution of Cd, and the Cd chemical forms. Meanwhile, Ca-K or Cd also affected the expressions of several metal transporters and changed the subcellular distribution of Zn. The differentially expressed metal transporters and changes in subcellular distributions and Cd chemical forms were associated with Cd and Zn uptake and translocation. In summary, the application of Ca-K caused changes in gene expression, Cd and Zn uptake, translocation, and subcellular distribution.

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