Biology Reference
In-Depth Information
9.4.4 Photoconversion of MV Pchlide a to MV
Chlorophyllide a in DMV-LDV-LDMV Plants
via Routes 10, 0
0
and 12
9.4.4.1 Photoconversion of MV Pchlide
a
to MV Chlorophyllide
a
via Route 10 in Greening DMDV-LDV-LDMV Plants
During the Light Phase of the Photoperiod
During the light phases of the photoperiod, in DMV-LDV-LDMV plant species such
as corn wheat and barley, MV Pchlide
a
can be formed from DV Pchlide
a
via route
10, which involves reduction of the vinyl group of DV Pchlide
a
at position 4 of the
macrocycle to ethyl, a reaction catalyzed by 4VPideR (Tripathy and Rebeiz
1986
).
The nascent MV Pchlide
a
can then be rapidly photoconverted to MV Chlide
a
most
probably by PORB which predominates in the light. The latter is active in green
tissues, and is assigned to route 10 on the basis of the continuous detection of DV
Pchlide
a
in the light, which in DMV-LDV-LDMV plant species is rapidly converted
to MV Pchlide
a
and MV Chlide
a
(Abd-El-Mageed et al.
1977
)(Fig.
9.5
).
a
9.4.4.2 Photoconversion of MV Pchlide
to MV Chlorophyllide
a
in DMV-LDV-LDMV Plants via Route 0
0
In this biosynthetic route, MV Chlide
a
is formed by photoconversion of MV
Pchlide. The Operation of biosynthetic route 0
0
in DMV-LDV-LDMV plants during
photoperiodic greening is justified by the detection and solubilization of 4-Vinyl
Mpe reductase (4VMpeR) in greening barley etiochloroplasts (Kolossov and
Rebeiz
2010
). Such etiochloroplasts can actively convert MV Mpe to MV Pchlide
a
(Tripathy and Rebeiz
1986
).
9.4.4.3 Photoconversion of MV Pchlide
a
to MV Chlorophyllide
a
in
DMV-LDV-LDMV Plants via Route 12 in Etiolated DMV-LDV-
LDMV Plants in Darkness, and in Greening DMV-LDV-LDMV
Plants During the Initial Dark Phases of the Photoperiod
Etiolated DMV-LDV-LDMV tissues accumulate massive amounts of MV Pchlide
a
in darkness and form most of their Chl via regenerated MV Pchlide
a
during the
dark and light cycles of the photoperiod (Abd-El-Mageed et al.
1977
; Carey and
Rebeiz
1985
; Tripathy and Rebeiz
1986
). In etiolated barley for example, the
resulting MV Pchlide
a
pool can be rapidly photoconverted to MV Chlide
a
(Belanger et al.
1982
). In etiolated tissues and during the initial dark phases of
the photoperiod when t-LW-Pchlide
a
accumulation is substantial (Cohen
et al.
1977
; Cohen and Rebeiz
1978
), the photoreduction of MV Pchlide
a
is most
probably catalyzed by PORA which predominates in etiolated tissues.
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