The TOR Pathway Modulates the Structure of Cell Walls inArabidopsis 

Abstract

Plant cell growth is limited by the extension of cell walls, which requires both the synthesis and rearrangement of cell wall components in a controlled fashion. The target of rapamycin (TOR) pathway is a major regulator of cell growth in eukaryotes, and inhibition of this pathway by rapamycin reduces cell growth. Here, we show that in plants, the TOR pathway affects cell wall structures. LRR-extensin1 (LRX1) of Arabidopsis thaliana is an extracellular protein involved in cell wall formation in root hairs, and lrx1 mutants develop aberrant root hairs. rol5 (for repressor of lrx1) was identified as a suppressor of lrx1. The functionally similar ROL5 homolog in yeast, Ncs6p (needs Cla4 to survive 6), was previously found to affect TOR signaling. Inhibition of TOR signaling by rapamycin led to suppression of the lrx1 mutant phenotype and caused specific changes to galactan/rhamnogalacturonan-I and arabinogalactan protein components of cell walls that were similar to those observed in the rol5 mutant. The ROL5 protein accumulates in mitochondria, a target of the TOR pathway and major source of reactive oxygen species (ROS), and rol5 mutants show an altered response to ROS. This suggests that ROL5 might function as a mitochondrial component of the TOR pathway that influences the plant's response to ROS.

Glutaredoxin GRXS17 Associates with the Cytosolic Iron-Sulfur Cluster Assembly Pathway

“…As reported previously, ctu1 and ctu2 T-DNA insertion lines did not contain thiolated tRNA ( Fig. 3C; Leiber et al, 2010;Philipp et al, 2014). In contrast, in grxs17-1 plants, levels of thiolated total tRNA were similar to wild type (Fig.…”

“…3A; Leidel et al, 2009;Philipp et al, 2014). Although only the protein encoded by AT2G44270 was described as the Arabidopsis CTU1 ortholog (Leiber et al, 2010), several peptides copurified with GRXS17 could not be distinguished from the product of locus AT1G76170 with 93% sequence similarity to CTU1 (Table I) and was named CTU1-like (CTU1L). To verify the interaction between GRXS17 and CTU1 and CTU2, we performed Y2H and BiFC assays.…”

“…grxs17-1 (SALK_021301), grxs17-2 (antisense line), rol5-2/ctu1-2 (GK-709D04), ctu2-2 (GK-686B10), elo3-6 (GK-555H06), met18-1 (SALK_121963), and met18-2 (SALK_147068) mutants were described previously (Leiber et al, 2010;Nelissen et al, 2010;Chen et al, 2011;Luo et al, 2012;Philipp et al, 2014). Arabidopsis (Arabidopsis thaliana) seeds were sterilized by the chlorine gas method and sown on sterile plates containing Murashige and Skoog medium supplemented with 1% (w/v) Suc, 0.8% (w/v) agarose, pH 5.7.…”

Arabidopsis Molybdopterin Biosynthesis Protein Cnx5 Collaborates with the Ubiquitin-like Protein Urm11 in the Thio-modification of tRNA

“…This may explain why many organisms have retained the two distinct types of Ubls for cytosolic tRNA thio-modification and MPT biosynthesis even though both types of proteins can be activated to form a thiocarboxylate at their C terminus and donate sulfur via the common Cnx5/MOCS3/Uba4-type sulfur transfer UBA proteins. As demonstrated previously, two additional conserved proteins, Ncs2 and Ncs6, in S. cerevisiae and the recently found plant Ncs6 ortholog (Rol5) (34) are also required for cytosolic tRNA thio-modification (6); therefore, they are potential candidates for Urm1 downstream sulfur acceptor proteins.…”

Cell wall integrity

“…[124][125][126][127] In addition, arabinogalactan proteins, COBRA and extensin-like receptor kinases are examples of GPI-containing proteins that are attached to the plasma membrane and implicated in connecting intracellular and extracellular space, thus affecting cell wall development. 17 These transmembrane receptor proteins are good candidates for transducing signals from the extracellular space to the cytoplasm.…”