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ABI4 downregulates expression of the sodium transporter HKT1;1 in Arabidopsis roots and affects salt tolerance
Author(s) -
ShkolnikInbar Doron,
Adler Guy,
BarZvi Dudy
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12091
Subject(s) - xylem , stele , mutant , arabidopsis , sodium , endodermis , microbiology and biotechnology , chemistry , biology , biochemistry , botany , gene , organic chemistry
Summary A plant's ability to cope with salt stress is highly correlated with their ability to reduce the accumulation of sodium ions in the shoot. Arabidopsis mutants affected in the ABSCISIC ACID INSENSITIVE ( ABI ) 4 gene display increased salt tolerance, whereas ABI 4 ‐overexpressors are hypersensitive to salinity from seed germination to late vegetative developmental stages. In this study we demonstrate that abi4 mutant plants accumulate lower levels of sodium ions and higher levels of proline than wild‐type plants following salt stress. We show higher HKT 1;1 expression in abi4 mutant plants and lower levels of expression in ABI 4 ‐overexpressing plants, resulting in reduced accumulation of sodium ions in the shoot of abi4 mutants. HKT 1;1 encodes a sodium transporter which is known to unload sodium ions from the root xylem stream into the xylem parenchyma stele cells. We have shown recently that ABI 4 is expressed in the root stele at various developmental stages and that it plays a key role in determining root architecture. Thus ABI 4 and HKT 1;1 are expressed in the same cells, which suggests the possibility of direct binding of ABI 4 to the HKT 1;1 promoter. In planta chromatin immunoprecipitation and in vitro electrophoresis mobility shift assays demonstrated that ABI 4 binds two highly related sites within the HKT 1;1 promoter. These sites, GC (C/G) GCTT (T), termed ABI 4‐binding element ( ABE ), have also been identified in other ABI 4 ‐repressed genes. We therefore suggest that ABI 4 is a major modulator of root development and function.