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were transplanted in 8 planters and 2 seedlings per planter with total of 16
seedlings. We observed that only 4 plants were growing in the case of wild-
type. However, in the case of R3-1 , 10 plants showed good growth. The
control experiment testing germination rates of the wild-type and the R3-1
mutant showed 90% of growth abilities in both lines, as indicated by Figure
1a.
D ISCUSSION
Phytochrome mediated responses of pea seedlings were extension of hook
and opening of first leaf. In the R3-1 mutant transit peptide-NDPK2 Ile12Leu
Glu205Lys working under the control of phytochrome (Hamada and
Hasunuma, 1994; Tanaka et al., 1998; Ogura et al., 1999) showed 2-fold
excessive phosphorylation and 2-fold excessive enzyme activity compared to
those of the wild-type transit peptide-NDPK2.
These phenomena could well explain the faster extension of hook and
faster opening of the first leaf in the R3-1 . The assumption of the function of
phytochrome is that phytochrome had open tetrapyrrole as the prosthetic
group, which will function as a photosensitizer (Hasunuma et al., 2012). The
acceptance of strong sunlight by phytochrome, as well as chlorophyll will
transfer the energy to ambient triplet oxygen 3 O 2 and generate singlet
oxygen ( 1 O 2 ), which moves with very fast speed to a length of 500µm. Singlet
oxygen will react with unsaturated fatty acids in plasma membrane forming
MDA (Haque et al., 2010) and vacuoler and microsomal menbranes generating
the channels for Ca 2+ . As a result, [Ca 2+ ]cyt will increase and mobilize the
cytoskeleton to open its hook and open the first leaf in the early stage of
seedlings. However, this process will not explain the faster opening of the
hook and faster opening of the first leaflet in R3-1 mutant than those in the
wild-type.
Rather catalases in the cytosol form complex with transit peptide-NDPK2
Ile12Leu Glu205Lys in the R3-1 , and rapidly moving singlet oxygen will be
captured by catalases. The capture of singlet oxygen by catalase resulted
negatively charged state in the catalase and there appear some space between
transit peptide-NDPK2 Ile12Leu Glu205Lys. Because catalase function as an
inhibitor of phosphorylation of transit peptide-NDPK2 in the wild-type, the
capture of singlet oxygen by catalase will make the inhibiting state to relaxed
state conferring the activity to accept ATP for autophosphorylation.
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