Multiple Quality Control Mechanisms in the ER and TGN Determine Subcellular Dynamics and Salt-Stress Tolerance Function of KORRIGAN1

Abstract

Among many glycoproteins within the plant secretory system, KORRIGAN1 (KOR1), a membrane-anchored endo-b-1,4glucanase involved in cellulose biosynthesis, provides a link between N-glycosylation, cell wall biosynthesis, and abiotic stress tolerance. After insertion into the endoplasmic reticulum, KOR1 cycles between the trans-Golgi network (TGN) and the plasma membrane (PM). From the TGN, the protein is targeted to growing cell plates during cell division. These processes are governed by multiple sequence motifs and also host genotypes. Here, we investigated the interaction and hierarchy of known and newly identified sorting signals in KOR1 and how they affect KOR1 transport at various stages in the secretory pathway. Conventional steady-state localization showed that structurally compromised KOR1 variants were directed to tonoplasts. In addition, a tandem fluorescent timer technology allowed for differential visualization of young versus aged KOR1 proteins, enabling the analysis of single-pass transport through the secretory pathway. Observations suggest the presence of multiple checkpoints/branches during KOR1 trafficking, where the destination is determined based on KOR1's sequence motifs and folding status. Moreover, growth analyses of dominant PM-confined KOR1-L 48 L 49 →A 48 A 49 variants revealed the importance of active removal of KOR1 from the PM during salt stress, which otherwise interfered with stress acclimation.

Complex-Type N-Glycans Influence the Root Hair Landscape of Arabidopsis Seedlings by Altering the Auxin Output

“…Especially glycoproteins that depend on complex-type N-glycan modification seem to be compromised in Arabidopsis and rice gntI mutants, leading to a reduced cellulose content ( Kang et al, 2008 ; Fanata et al, 2013 ). Moreover, impairments in complex N-glycosylation affect the function and stability of KORRIGAN1, a glycoprotein with eight mostly complex N-glycans ( Kang et al, 2008 ; Liebminger et al, 2013 ; Rips et al, 2014 ; Nagashima et al, 2020 ; Kaulfürst-Soboll et al, 2021 ), which plays an important role for cellulose synthesis at the PM ( Nicol et al, 1998 ; Sato et al, 2001 ).…”

Journey and Destination: KORRIGAN1 Subcellular Localization Dynamically Changes during Plant Growth and Stress Tolerance

“…For example, when there are mutations in the catalytic extracellular domain, KOR1 accumulates at the tonoplast (TP), likely for subsequent degradation (Rips et al, 2014). Nagashima et al (2020) investigated the multiple determinants for the subcellular localization of KOR1 and the related physiological significance in plant growth and stress tolerance. Nagashima et al (2020) identified a C-terminal Pro-rich motif (termed the P-motif) that retains KOR1 in the TGN network/PM cycle.…”

“…Nagashima et al (2020) investigated the multiple determinants for the subcellular localization of KOR1 and the related physiological significance in plant growth and stress tolerance. Nagashima et al (2020) identified a C-terminal Pro-rich motif (termed the P-motif) that retains KOR1 in the TGN network/PM cycle. To explore the development of KOR1, the authors created an estradiol-inducible KOR1 reporter construct with a tandem fluorescent timer (tdFT) protein to induce de novo synthesis and monitor newly synthesized and aged KOR1 en route to its final destination(s).…”

“…Scale bars 5 10 mm. (Adapted from Nagashima et al [2020], Figure 2.) [OPEN] Articles can be viewed without a subscription.…”

“…This indicates the need for saltinduced subcellular internalization of KOR1, and potentially subsequent activity, for establishing stress-acclimated root growth. Nagashima et al (2020) show the regulation of subcellular dynamics of KOR1 via various modified regulatory motifs, identified by the use of tdFT analysis. This study reveals new insight into how the fine-tuning of KOR1 localization and activity may be necessary for plants to adapt to salt stress.…”