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Effects of modulating endogenous polyamines on stress response
Changes in cellular polyamines under stress only provide
clues on its possible implication in stress response, but
they do not provide evidence of its role in counteracting
stress. Therefore, in order to understand whether
polyamines actually protect cells from stress-derived
injuries, an exogenous application of polyamines, which
is expected to increase endogenous polyamines, has been
attempted before or during stress (Borrel et al. 1996;
Velikova et al. 1998, 2000; Navakoudis et al. 2003; Wang
et al. 2006). Most of this research demonstrated that
exogenous polyamines could, in varying degrees, reverse
growth or minimize growth inhibition caused by stress,
indicating that polyamines are effective at mitigating
stress-derived cell injury. However, the protective effects
of individual polyamines are somewhat different. For
example, Spm and/or Spd was shown to be effective for
reversing the inhibitory effect of acid rain (pH 1.
on
bean (Velikova et al. 1998, 2000), mitigating salt injury
on wheat (Iqbal and Ashraf 2005), reducing ozonederived
injury on potato (Ormord and Beckerson 1986),
and enhancing copper tolerance in Nymphoides peltatum
(Wang et al. 2006). In contrast, Tang and Newton (2005)
and Ndayiragije and Lutts (2006) reported that Put was
more effective for reducing salt-induced oxidative
damage in Virginia pine and alleviating NaCl-derived
cell damage in rice, respectively.
Plant species or cultivars
Under stress, different plant species vary in theirChanges in cellular polyamines under stress only provide
clues on its possible implication in stress response, but
they do not provide evidence of its role in counteracting
stress. Therefore, in order to understand whether
polyamines actually protect cells from stress-derived
injuries, an exogenous application of polyamines, which
is expected to increase endogenous polyamines, has been
attempted before or during stress (Borrel et al. 1996;
Velikova et al. 1998, 2000; Navakoudis et al. 2003; Wang
et al. 2006). Most of this research demonstrated that
exogenous polyamines could, in varying degrees, reverse
growth or minimize growth inhibition caused by stress,
indicating that polyamines are effective at mitigating
stress-derived cell injury. However, the protective effects
of individual polyamines are somewhat different. For
example, Spm and/or Spd was shown to be effective for
reversing the inhibitory effect of acid rain (pH 1.
onbean (Velikova et al. 1998, 2000), mitigating salt injury
on wheat (Iqbal and Ashraf 2005), reducing ozonederived
injury on potato (Ormord and Beckerson 1986),
and enhancing copper tolerance in Nymphoides peltatum
(Wang et al. 2006). In contrast, Tang and Newton (2005)
and Ndayiragije and Lutts (2006) reported that Put was
more effective for reducing salt-induced oxidative
damage in Virginia pine and alleviating NaCl-derived
cell damage in rice, respectively.
Plant species or cultivars
response in terms of polyamine fluctuation. Some might
accumulate polyamines in response to stress, while
others do not or even decrease their endogenous
polyamine contents when exposed to harsh
environments. When suspensions of tobacco and alfalfa,
which differed in thermosensitivity, were exposed to
heat, they showed differences in the accumulation of free
or conjugated polyamines (Königshofer and Lechner
2002). In addition, cultivars from the same species
differing in stress sensitivity might also show a diverse
change in the pattern of polyamines under stress.
Krishnamurthy and Bhagwat (1989) compared
polyamine accumulation of nine rice cultivars with
different salt sensitivity, in which they showed that the
118 Polyamines and their ability to provide environmental stress tolerance to plants
Figure 1. Pathways of polyamine biosynthesis (A) and degradation (B). ADC, arginine decarboxylase; dcSAM, decarboxylated Sadenosylmethionine;
ODC, ornithine decarboxylase; DAO, diamine oxidase; PAO, polyamine oxidase; SAM, S-adenosylmethionine; SAMDC, Sadenosylmethionine
decarboxylase; SPDS, spermidine synthase; SPMS, spermine synthase.
salt-tolerant cultivars accumulated high concentrations of
Spd and Spm, while the salt-sensitive ones accumulated
excessive Put and low levels of Spd and Spm. Liu et al.
(2004) reported that, when two wheat cultivars with
different degrees of drought tolerance were treated with
PEG, a marked increase in free Spd and Spm was
observed in the tolerant cultivar, while a significant
increase in free Put was detected in the sensitive cultivar.
Similar results were also reported in groundnut by
Vakharia et al. (2003) and in tomato by Santa-Cruz et al.
(199
.Polyamines and their ability to provide environmental stress
tolerance to plants
Ji-Hong Liu1, Hiroyasu Kitashiba2, Jing Wang1, Yusuke Ban3, Takaya Moriguchi3,4,*
1 National Key Laboratory of Crop Genetic Improvement, National Center of Crop Molecular Breeding, Huazhong
Agricultural University, Wuhan 430070, China; 2 Graduate School of Agricultural Science, Tohoku University, Sendai,
Miyagi 981-8555, Japan; 3 Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba,
Ibaraki 305-8572, Japan; 4 National Institute of Fruit Tree Science, Tsukuba, Ibaraki 305-8605, Japan
To stress or not to stress?
thats my question to you guys