Abstract
Patterned cell wall deposition is crucial for cell shapes and functions. In Arabidopsis xylem vessels, ROP11 GTPase locally inhibits cell wall deposition through microtubule disassembly, inducing pits in cell walls. Here, we show that an additional ROP signaling pathway promotes cell wall growth at pit boundaries. Two proteins, Boundary of ROP domain1 (BDR1) and Wallin (WAL), localize to pit boundaries and regulate cell wall growth. WAL interacts with F-actin and promotes actin assembly at pit boundaries while BDR1 is a ROP effector. BDR1 interacts with WAL, suggesting that WAL could be recruited to the plasma membrane by a ROP-dependent mechanism. These results demonstrate that BDR1 and WAL mediate a ROP-actin pathway that shapes pit boundaries. The study reveals a distinct machinery in which two closely associated ROP pathways oppositely regulate cell wall deposition patterns for the establishment of tiny but highly specialized cell wall domains.
Highlights
Patterned cell wall deposition is crucial for cell shapes and functions
To identify potential factors connecting Rho-like GTPase from plant 11 (ROP11) signaling with the pit boundary, uncharacterized genes that were upregulated during metaxylem vessel differentiation in Arabidopsis[22] were identified, and the subcellular localization of their products in metaxylem vessel cells was investigated[23]
Induction for 2 days with estrogen resulted in the loss of pit localization of Boundary of Rho-like GTPases from plant (ROP) domain1 (BDR1)-tagRFP and uniform localization of BDR1-tagRFP in xylem vessel cells in association with GFP-ROP11G17V (Supplementary Figure 4), demonstrating that activated ROP11 could direct the localization of BDR1. These results indicate that the ROP-BDR-WAL-actin pathway is the central component of the machinery promoting cell wall deposition at pit boundaries (Fig. 4e)
Summary
Patterned cell wall deposition is crucial for cell shapes and functions. In Arabidopsis xylem vessels, ROP11 GTPase locally inhibits cell wall deposition through microtubule disassembly, inducing pits in cell walls. BDR1 interacts with WAL, suggesting that WAL could be recruited to the plasma membrane by a ROPdependent mechanism These results demonstrate that BDR1 and WAL mediate a ROP-actin pathway that shapes pit boundaries. Rho-like GTPases from plant (ROP) control cell wall deposition pattern by governing the behavior of microtubules[3,4,5,6] and actin filaments[6,7,8,9,10,11,12,13,14], which thereby determines cell shapes and functions[15,16,17].
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