Dynamic Aspects of Ion Accumulation by Vesicle Traffic Under Salt Stress in Arabidopsis

Abstract

The intracellular membrane dynamics of Arabidopsis cells under high salt treatment were investigated. When Arabidopsis was treated with high levels of NaCl in hydroponic culture, root tip cells showed rapid changes in the vacuolar volume, a decrease in the number of small acid compartments, active movement of vesicles and accumulation of Na(+) both in the central vacuole and in the vesicles around the main vacuole observed with the Na(+)-dependent fluorescence of Sodium Green. Detailed observation of Arabidopsis suspension-cultured cells under high salt treatment showed a similar pattern of response to that observed in root tip cells. Immunostaining of suspension-cultured cells with antibodies against AtNHX1 clearly showed the occurrence of dotted fluorescence in the cytoplasm only under salt treatment. We also confirmed the existence of AtNHX1 in the vacuolar membrane isolated from suspension-cultured cells with immunofluorescence. Knockout of the vacuolar Q(a)-SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein VAM3/SYP22 caused an increase in salt tolerance. In mutant plants, the distribution of Na(+) between roots and shoots differed from that of wild-type plants, with Na(+) accumulating more in roots and less in the shoots of the mutant plants. The role of vesicle traffic under salt stress is discussed.

Salt-Induced Remodeling of Spatially Restricted Clathrin-Independent Endocytic Pathways in Arabidopsis Root

“…No large vacuole-like bodies accumulated stain in endodermis or stele, which have small, dispersed acidic vesicles ( Figure 7A, right). However, on treating the plants with 100 mM NaCl for 24 h, vacuolar structures in the cortex became more extensive, consistent with previous reports (Hamaji et al, 2009). In addition, large acidic compartments, reminiscent of vacuoles, were seen in the endodermis and the stele (Figure 7B, right).…”

“…In the meristematic region of control plants, only the epidermal layer has a well-developed and extensive vacuolar structure, Salt Alters Endocytosis in Arabidopsiswith rather smaller vacuoles seen in the cortex (Hamaji et al, 2009). Staining roots with LysoTracker Red, which stains acidic compartments (Laxmi et al, 2008), recapitulated these earlier findings ( Figure 7A).…”

“…In the stele region, the vacuolar area increased almost 2.5-fold (from 22% of stele cells under control conditions compared with 56% of the cellular area after 24 h of salt stress) in response to salt ( Figure 7E). We also observed the vacuolar structures in the stele using the GFP-tagged form of the vacuolar SNARE SYP22 (Hamaji et al, 2009); salt stress for 24 h caused a similar expansion of vacuolar structures marked with SYP22-GFP in stele cells (Supplemental Figure 12) compared with control plants, where the vacuoles in stele cells appear to be organized in thin tubular structures (Viotti et al, 2013). Intriguingly, in the vps9a-2 mutant, wherein induction of salt-induced clathrin-independent endocytosis is inhibited, salinity-induced development of vacuolar structures in the inner cell layers was also not observed ( Figures 7C to 7E).…”

TNO1 Is Involved in Salt Tolerance and Vacuolar Trafficking in Arabidopsis

“…Knockdown of AtVAMP7C, a v-SNARE involved in vesicle fusion with the vacuole, was found to confer salt tolerance by preventing hydrogen peroxidecontaining vesicles from fusing with the tonoplast (Leshem et al, 2006). Knockout of SYP22, a t-SNARE in the PVC and tonoplast, also increased salt tolerance in shoots, and a decreased level of Na + in shoots was observed (Hamaji et al, 2009). Thus, vesicle fusion appears to directly or indirectly affect salt tolerance at the PVC and vacuoles.…”

Acclimation improves salt stress tolerance in Zea mays plants

“…Vacuolar NHX proteins (NHX1 and NHX2; NHX = Na + /H + exchanger) are considered the main players in sodium compartmentalization in the vacuoles (Apse et al, 1999(Apse et al, , 2003Blumwald, 2000). More recently, vesicle trafficking has been described as a contributor for sodium compartmentation (Liu et al, 2007;Hamaji et al, 2009;Qiu, 2012). Control of Na + -permeable slow (SV) and fast (FV) vacuolar channels is also essential for effective Na + retention in vacuole (Bonales-Alatorre et al, 2013).…”