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Plant Physiol. 2018 Mar;176(3):1981-1992. doi: 10.1104/pp.17.01374. Epub 2017 Dec 15.

LRX Proteins Play a Crucial Role in Pollen Grain and Pollen Tube Cell Wall Development.

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Institute of Plant and Microbial Biology and Zurich-Basel Plant Science Center, University of Zurich, 8008 Zurich, Switzerland.
Computational Physics for Engineering Materials Group, Institute for Building Materials, ETH Zürich, 8093 Zurich, Switzerland.
Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, LS2 9JT Leeds, United Kingdom.
Institute of Plant and Microbial Biology and Zurich-Basel Plant Science Center, University of Zurich, 8008 Zurich, Switzerland


Leu-rich repeat extensins (LRXs) are chimeric proteins containing an N-terminal Leu-rich repeat (LRR) and a C-terminal extensin domain. LRXs are involved in cell wall formation in vegetative tissues and required for plant growth. However, the nature of their role in these cellular processes remains to be elucidated. Here, we used a combination of molecular techniques, light microscopy, and transmission electron microscopy to characterize mutants of pollen-expressed LRXs in Arabidopsis (Arabidopsisthaliana). Mutations in multiple pollen-expressed lrx genes cause severe defects in pollen germination and pollen tube growth, resulting in a reduced seed set. Physiological experiments demonstrate that manipulating Ca2+ availability partially suppresses the pollen tube growth defects, suggesting that LRX proteins influence Ca2+-related processes. Furthermore, we show that LRX protein localizes to the cell wall, and its LRR-domain (which likely mediates protein-protein interactions) is associated with the plasma membrane. Mechanical analyses by cellular force microscopy and finite element method-based modeling revealed significant changes in the material properties of the cell wall and the fine-tuning of cellular biophysical parameters in the mutants compared to the wild type. The results indicate that LRX proteins might play a role in cell wall-plasma membrane communication, influencing cell wall formation and cellular mechanics.

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