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Legume Genomics and Genetics (online), 2010, Vol. 1, No.5, 24-29
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constitutive expression of
HvPIP2
;
1
raised salt sensi-
tivity of transgenic rice (Katsuhara et al., 2003).
Peanut is one of the major oilseed crops in the world,
and the increase of the soil salinity might heavily limit
its yield. To study the molecular mechanisms of pea-
nut to salt tolerance, in this research, we isolated seve-
ral salt-inducible genes from the salt tolerant variety
Huayu28, and then one of them, an aquaporin ene,
was chosen for further characterization.
1 Results
1.1 Cloning and characterization of
AhAQ1
gene
The full length of
AhAQ1
gene was cloned from salt-
treated peanut leaves by RT-PCR technology.
AhAQ1
encodes a protein consisting of 287 amino acids with
the calculated molecular mass of 30.57 kD and the
isoelectric point of 9.04 (Figure 1). Sequence analysis
of deduced amino acids indicated that AhAQ1 was an
highly hydrophobic with 6 possible transmembrane
domains linked by loop A~E, and two NPA boxes, which
can be found in most aquaporins that lies in loop B
and loop E (Figure 2). A comparison used the deduced
amino acids of AhAQ1 as a queryprobe to search gene
database (http://www.ncbi.nlm.nih.gov) though blastp
algorithm program showed that AhAQ1 was more
similar to the PIP2 family. Multiple sequence align-
ment showed that the amino acid sequence of AhAQ1
was highly conserved in other PIP2s from maize,
barley, tobacco, Arabidopsis
and olive, especially in
the transmembrane domains (Figure 3).
To investigate the evolutionary relationships among
plant aquaporins, a phylogenetic tree was constructed
using a neighbor-joining method with the full-length
amino acid residues (Figure 4). The result showed that
AhAQ1 was grouped into the big branch of PIP2-type
proteins, which including AtPIP2;3, ZmPIP2;1, HvPIP2;1,
OePIP2;1, BoPIP3 and NtPIP2;1. On the other hand,
PIP1 proteins including NtPIP1;1, AtPIP1;1, BoPI
P1b1, OePIP1;1, ZmPIP1;2 and HvPIP1;1, which have
longer N-terminal extensions and shorter C-terminal
ends compared with the PIP2 proteins (Schaffner,
1998), were categorized into another big branch.
1.2 Expression of
AhAQ1
in response to high salt stress
The expression pattern of
AhAQ1
in peanut tissues
under high salt treatment was examined by semi-
Figure 1 Nucleotide sequences and deduced amino acid residues of AhAQ1
Note: The amino acid residues are indicated by a single letter code; The transmembrane domains and NPA motifs are underlined and
double-underlined, respectively
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