MOLECULAR MECHANISMS OF SALT TOLERANCE IN MANGROVE PLANTS - Agricultural Research Updates - page 81

stress [44], and those that constitutively expressed glutathione-S-transferase
were resistant to both cold and salt stresses [45]. There are several reports of
the up-regulation of antioxidative enzymes and their corresponding genes in
mangroves under saline conditions (Table 2). In B. gymnorhiza , there is an
immediate increase in the activities of the antioxidant enzymes SOD and CAT
after salt treatment [13]. Salt-treated B. gymnorhiza also shows induction of
mRNAs encoding cytosolic Cu/Zn-SOD and CAT [46]. In B. parviflora , salt
treatment preferentially enhances H 2 O 2 content as well as the activity of APX,
GPX, GR and SOD, whereas it decreases CAT activity [42]. Jithesh et al . [43]
used mRNA expression analysis to study changes in the expression of the A.
marina antioxidant genes that encode Cu-Zn SOD ( Sod1 ), catalase ( Cat1 ), and
ferritin ( Fer1 ) in response to salt, iron, hydrogen peroxide, mannitol and light
stress (Table 2).

Table 2. Molecular researches of the antioxidant production in
mangroves. Modified from Tada [57]

Mangrove
species

Methods Genes/proteins Description References

Enhanced gene
expression under
osmotic stress but not
under salinity.

Cu/Zn superoxide
dismutase (sod1)

cDNA
cloning and
Northern
analysis

Avicennia
marina

[43]

Enhanced gene
expression under
salinity and oxidative
stress.

Cat1 (catalase)
Fer1(ferritin)

LAS (lipoic acid
synthase)

Enhanced gene
expression under salt
stress.

Differential
display

[29]

Dihydrolipoamide
dehydrogenase

Enhanced enzyme
activity under salinity
stress.

Bruguiera
gymnorhiza

Enzyme
assay

SOD
Catalase

[13]

cDNA
cloning and
Northern
analysis

Enhanced gene
expression with salt,
mannitol and ABA
treatments.

Cu/Zn SOD
Catalase

[46]

In response to NaCl stress, Cat1 and Fer1 expression were induced for a
short period, while Sod1 transcript levels were unaltered. Sod1 , Cat1 and Fer1
mRNA levels were induced by iron, light stress and direct H 2 O 2 stress
treatment, thus confirming their role in the oxidative stress response. In B.