Clapham, "Genome-wide RNAi screen identifies Letm1 as a mitochondrial [Ca.sup.2+]/[H.sup.+] antiporter
," Science, vol.
In addition, many other genes, including NHA1 (encoding a [Na.sup.+]/[H.sup.+] antiporter
located at the plasma membrane), TRK1/TRK2 (encoding [K.sup.+] transporters located at the plasma membrane), and NHX1 (encoding a [Na.sup.+]/[H.sup.+] antiporter
localized in the vacuole), also participate in the salt stress response [24, 25].
Net [Na.sup.+] uptake in the roots is mediated by antiporters
or ion channel-type transporters (HKT, LCT1 and NSCC).
Among them, [Na.sup.+]/[H.sup.+] antiporter
genes have been proved to play an important role in salt tolerance, which are considered as promising genes for breeding salt-tolerant crops via genetic engineering.
System [b.sup.0,+], one of the heterodimeric amino acid transporters (HATs), is composed of a heavy subunit (related to [b.sup.0,+] amino acid transport, rBAT) and a light subunit ([b.sup.0,+] amino acid transport, [b.sup.0,+]AT), which mediates high-affinity transport of cystine and cationic amino acids in a tightly coupled equimolar exchange with neutral amino acids in the plasma membrane as antiporters
(Chillaron et al., 2001; Kanai1 et al., 2001; Wagner et al., 2001).
During the premolt phase, calcium solubilized from the old exoskeleton enters the hemolymph and, following its electrochemical gradient, flows into hepatopancreatic cells through channels or reversal antiporters
in the basolateral membrane (Wheatly, 1999; Zanotto and Wheatly, 2003).
These NSTs are antiporters
in which nucleotide sugar entry into the ER/Golgi is coupled to equimolar exit of the corresponding nucleoside monophosphate from the ER/Golgi lumen (38).
Hence, the wildtype ABI2 may negatively regulate salt tolerance either by inactivating SOS2, or the SOS2 regulated [Na.sup.+]/[H.sup.+] antiporters
such as SOS1 or NHX1 (Fig.
Based on transport mode, MFS transporters are divided into three main groups: uniporters which transport a single substrate; symporters which transport a substrate in association with a coupling ion; and antiporters
which transport a substrate and a cosubstrate in opposite directions .
hydrolysis or indirectly as symporters and antiporters
(Morth et al.,
Differential expression and nction of Arabidopsis thaliana NHX Na+/H+ antiporters
in the salt stress response.
In saline soils, [Na.sup.+] that entered root cells in the outer part of root was likely pumped back out again via plasma membrane [Na.sup.+]/[H.sup.+] antiporters
encoded by the gene SOS1 .