Abstract
Regulation of plant cell wall deposition and patterning is essential for the normal growth and development of plants. Small GTPases play pivotal roles in the modulation of primary cell wall formation by controlling cytoskeletal organization and membrane trafficking. However, the functions of small GTPases in secondary cell wall development are poorly understood. Recent studies on xylem cells revealed that the Rho of plants (ROP) group of small GTPases critically participates in the spatial patterning of secondary cell walls. In differentiating xylem cells, a specific GTPase-activating protein (GAP)/guanine nucleotide exchange factor (GEF) pair facilitates local activation of ROP11 to establish de novo plasma membrane domains. The activated ROP11 then recruits a microtubule-associated protein, MIDD1, to mediate the mutual inhibition between cortical microtubules and active ROP. Furthermore, recent works suggest that certain small GTPases, including ROP and Rab GTPases, regulate membrane trafficking to establish secondary cell wall deposition and patterning. Accordingly, this mini-review assesses and summarizes the current literature regarding the emerging functions of small GTPases in the development of secondary cell walls.
Highlights
Post-embryonic development of plants requires prominent cell growth and cell differentiation phases, during which cells dramatically increase their volume and assume appropriate shapes and functions
Co-introduction of ROPGEF4, ROPGAP3, and ROP11 into non-xylem cells resulted in the presence of disperse spots of active ROP11 on the plasma membrane in a manner reminiscent of the localization of active ROP11 in xylem cells. These findings demonstrate that ROPGEF4 and ROPGAP3 mediate de novo local activation of ROP11 to establish the fundamental patterning of secondary cell wall pits (Oda and Fukuda, 2012a)
Expression data indicate that at least eight Rho of plants (ROP) including ROP11 are expressed in xylem cells (Winter et al, 2007).Because ROP11 functions in ROP/MIDD1/kinesin-13A signaling to form secondary cell wall pits, ROPs other than ROP11 may participate in secondary cell wall development
Summary
Reviewed by: Viktor Zarsky, Charles University, Czech Republic Stephanie Robert, SLU/Umeå Plant Science Center, Sweden. The functions of small GTPases in secondary cell wall development are poorly understood. Recent studies on xylem cells revealed that the Rho of plants (ROP) group of small GTPases critically participates in the spatial patterning of secondary cell walls. A specific GTPase-activating protein (GAP)/guanine nucleotide exchange factor (GEF) pair facilitates local activation of ROP11 to establish de novo plasma membrane domains. Recent works suggest that certain small GTPases, including ROP and Rab GTPases, regulate membrane trafficking to establish secondary cell wall deposition and patterning. This mini-review assesses and summarizes the current literature regarding the emerging functions of small GTPases in the development of secondary cell walls
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