Biology Reference
In-Depth Information
10.1.3.2 Biosynthesis of MV Chlorophyll
in DDV-LDV-LDDV
Plants via a Combination of Routes 1 and 3 in Etiolated
DDV-LDV-LDDV Plants After Exposure to Light
a
During prolonged dark-incubation of DDV-LDV-LDDV plants, small amounts of
MV Pchlide
a
are formed via route 3. Upon exposure to light, MV Pchlide
a
is
photoconverted to MV Chlide
a
by PORA. Most probably, conversion of the
nascent MV Chlide
a
to MV Chl a via route 3 takes place via Chl a-GG followed
by stepwise hydrogenation to Chl
a
-Phytol. Since during the initial phases of
greening of etiolated tissues, most of the Chl consists of MV Chl
a
, located in
PSI and PSII (Akoyunoglou et al.
1981
; Alberte et al.
1972
), we propose that
the MV Chl
a
formed via route 3 is destined to PSI and/or PSII Chl-protein
complexes.
10.1.3.3 Biosynthesis of MV Chlorophyll
in DDV-LDV-LDDV Plants
via a Combination of Routes 1, 4, and 5 in Etiolated Plants
After Exposure to Light, and in Greening Plants During
the Initial Dark Phases of the Photoperiod
a
Etiolated DDV-LDV-LDDV plants accumulate mostly DV Pchlide
a
. Upon exposure
to light, DV Pchlide
a
is converted to DV Chlide
a
by PORA via route 1. Then DV
Chlide
a
is converted to MV Chlide
a
via route 4 by 4-vinyl reduction catalyzed by
4VCR, and finallyMVChlide a is converted toMVChl
a
via route 5. Since in etiolated
tissues, MV Chlide
a
conversion to MV Chl
a
takes place via esterification with GG
(Schoch
1978
), it is our guess that, conversion of the nascent MV Chlide
a
to MV Chl
a
via route 5 takes place via Chl
a
-GG followed by stepwise hydrogenation to Chl
a
-
Phytol as described in Sect.
1.1
. This route is also most probably functional in
DDV-LDV-LDDV plants growing under photoperiodic conditions, at the onset of
illumination, during the first few dark cycles of the photoperiod when t-LW-Pchlide
a accumulation is substantial (Cohen et al.
1977
; Cohen and Rebeiz
1978
). Since during
the initial phases of greening of etiolated tissues, most of the Chl consists of MV Chl
a
,
located in PSI and PSII (Akoyunoglou et al.
1981
; Alberte et al.
1972
), we propose
that the MV Chl
a
formed via route 3 is destined to PSI and/or PSII Chl-protein
complexes.
10.1.3.4 Biosynthesis of MV Chlorophyll
in DDV-LDV-LDDV Plants
via Route a Combination of Routes 1 and 7 in Etiolated Plants
After Exposure to Light, and in Greening Plants During
the Initial Dark Phases of the Photoperiod
a
In etiolated DDV-LDV-LDDV plants exposed to light, DV Pchlide
a
is converted
to DV Chlide
a
by PORA via route 1. Then DV Chlide
a
is rapidly converted to MV
Search WWH ::
Custom Search