Agriculture Reference
In-Depth Information
shock N-terminal domain-containing protein. It has been reported previously
that enhanced expression of the
B. gymnorhiza
gene encoding LAS occurs
under saline conditions [29]. The gene that encoded LTP was also up-
regulated in
B. gymnorhiza
by salt treatment, and its overexpression conferred
enhanced salt tolerance to
Agrobacterium
and
Arabidopsis
[61]. These results
strongly suggest that LAS and LTP participate in salt tolerance in
B.
gymnorhiza
. A metallothionein-like protein might also contribute to ROS
scavenging, thereby increasing the tolerance of mangroves to salt stress.
Clones encoding ribulose 1,5-bisphosphate carboxylase and DNAJ heat shock
N-terminal domain-containing protein were among the 107 putative salinity-
tolerance genes identified by
E. coli
functional assay of cDNAs from
Acanthus
ebracteatus
[63]. The identification of these photosynthesis- and heat shock-
related proteins in two independent mangrove species by bacterial functional
screening [62, 63] suggests that these proteins may have unknown roles in
conferring salinity tolerance.
Putative salinity tolerance genes have been isolated from
B. cylindrica
using suppressive subtractive hybridization (SSH) and functional screening in
bacteria [64]. In this study, 75 cDNA sequences from
B. cylindrica
were
identified that conferred salinity tolerance to
E. coli
. These cDNAs contained
29 genes that encoded proteins with putative functions in transportation and
metabolism, as well as 33 genes that encoded proteins of unknown function.
Bacterial functional screening of two mangrove species,
A. ebracteatus
and
B. gymnorhiza
, resulted in the identification of some coincident candidate
genes for salt tolerance [62, 63]; however, there was little coincidence among
the clones identified by other functional screenings of
B. sexangula
and
B.
cylindrical
[58-60, 64].
2.4.2. Transcriptional Analysis of Mangroves
Transcriptional analyses, including EST analysis and microarray analysis,
have been used to identify genes involved in salt tolerance in mangroves
(Table 4). Because mangroves are capable of responding to salt stress through
the activation of salt-tolerant or salt-adaptive mechanisms, a rational approach
is to analyze salt-responsive genes from mangrove species as candidate salt
tolerance genes. Differential screening of cDNAs from salt-treated and non-
treated mangroves has been performed to identify these salt-responsive genes.
Representational difference analysis of cDNA was used to identify ten
salt-responsive cDNAs from
K. candel
[65]. Of five genes expressed
preferentially under saline conditions, two were unknown, two were forms of
low molecular mass heat-shock proteins (sHSPs), and one was an ADP-
