Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 24 (4), 511-22

Na+/myo-inositol Symporters and Na+/H+-antiport in Mesembryanthemum Crystallinum


Na+/myo-inositol Symporters and Na+/H+-antiport in Mesembryanthemum Crystallinum

S Chauhan et al. Plant J.


Mitr1 and Mitr2 from Mesembryanthemum crystallinum (common ice plant) are members of a family of genes homologous to H+[or Na+]/myo-inositol symporters (ITRs), not previously studied in plants. MITR1 complemented an Itr1-deficient yeast strain. Mitr1 is strongly expressed in roots, moderately in stems, and weakly in leaves. Its transcripts increased in all organs, most dramatically in roots, under salinity stress. Mitr2 constitutes a rare transcript, slightly upregulated by salt stress in leaves only. Mitr1 transcripts are present in all cells in the root tip, but become restricted to phloem-associated cells in mature roots. Peptide antibodies against the two proteins indicated the presence of MITR1 in all organs and of MITR2 in leaves. Both are located in the tonoplast. MITR1 acts in removing sodium from root vacuoles, correlated with findings of low root sodium, while leaf vacuoles accumulate sodium in the ice plant. Up-regulation in leaves and stems is also found for Na+/H+-antiporter (Nhx-type) transcripts. Under comparable stress conditions, Nhx-and Itr-like transcripts in Arabidopsis were regulated differently. In the ice plant, co-ordinate induction of Na+/H+-antiporters and Na+/myo-inositol symporters transfers sodium from vacuoles in root cells into the leaf mesophyll as a halophytic strategy that lowers the osmotic potential. The tissue-specific differential expression of Itr- and Nhx-type transcripts suggests that the vacuolar sodium/inositol symporters function to reduce sodium amounts in cells of the root and vascular tissue, while sodium/proton antiporters in leaf tissues function to partition sodium into vacuoles for storage.

Similar articles

See all similar articles

Cited by 32 PubMed Central articles

See all "Cited by" articles

Publication types

MeSH terms

Associated data

LinkOut - more resources