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region of the enzyme. We established that NDPKs in the membrane fraction
and soluble fraction were signal transducers of phytochromes (Hamada and
Hasunuma 1994; Tanaka et al., 1998; Ogura et al., 1999). The results of signal
transduction of phytochrome in various plants are well known to increase in
[Ca
2+
]cyt from unknown storage site of Ca
2+
(Shacklock et al., 1992). The
transient increases in Ca
2+
concentration in the cytosol via the phytochrome
has been well established, although no information on the release of Ca
2+
from
Ca
2+
storage sites was presented.
As a photoreceptor with an open tetrapyrrole as the prosthetic group,
phytochrome will function as a photosensitizer and red light energy adsorbed
by phytochrome will be transferred to an ambient triplet oxygen (
3
O
2
) emitting
singlet oxygen, (
1
O
2
), which will move very fast at a range of 500 µm over the
region of neighboring cell (Luksiene 2003; Ayaru et al., 2005; Hasunuma et
al., 2012) and may react with unsaturated fatty acids in the vacuolar and
microsomal membranes, as well as the plasma membrane. The reaction of the
singlet oxygen to the double bond of unsaturated fatty acids, which forms
malone-dialdehyde (MDA) in the vacuolar and plasma membranes (Haque et
al., 2010), facilitates pore formation, permitting the influx of Ca
2+
to the
cytosol and the release of Ca
2+
from the vacuole and the microsome to the
cytosol, thus increasing the [Ca
2+
]cyt.
We have also established that the singlet oxygen emitted by the
phytochrome will be captured by catalases in the cytosol. The catalases in the
cytosol formed a protein complex, with NDPK functioning as an inhibitor of
NDPK phosphorylation (Fukamatsu et al., 2003; Yoshida et al., 2006; Wang et
al., 2007; Haque et al., 2008; Haque et al., 2010). By the acceptance of the
singlet oxygen by catalase, catalase binds the singlet oxygen making it
negatively charged, and causing some space in the catalase/NDPK protein
complex (Fukamatsu et al., 2003; Yoshida et al., 2006; Haque et al., 2010) and
facilitating it to accept ATP and allow phosphorylation. NDPK has also been
demonstrated to bind NADH (Wang et al., 2007; Haque et al., 2010) and
therefore NDPK/NADH will transfer electrons to catalase/singlet oxygen,
releasing superoxide (O
2
.-
) (Hasunuma et al., 2011). The resulting superoxide
will react with the unsaturated fatty acids of the vacuolar and microsomal
membranes and plasma membrane forming MDA (Haque et al., 2010); pores
are formed that permit the influx of Ca
2+
via plasma membrane and the release
of Ca
2+
to the cytosol from calcium storage sites of vacuole and microsome
increasing [Ca
2+
]cyt.
The increase in [Ca
2+
]cyt resulted in the increase in the respiration by
mitochondria, resulting in the production of a greater amount of ATP and the
