Agriculture Reference
In-Depth Information
Fig. 17.1
Schematic representation of PA biosynthetic pathways in plants.
ADC
arginine decar-
boxylase,
AIH
agmatine iminohydrolase,
CPA
N-carbamoylputrescine amidohydrolase,
ODC
ornithine decarboxylase,
SPDS
spermidine synthase,
SPMS
spermine synthase,
SAM synthase
S
-adenosylmethionine synthase,
SAMDC
S
-adenosylmethionine decarboxylase,
ACC synthase
1-amino-cyclopropane-1-carboxylic-acid synthase,
ACC oxidase
1-amino-cyclopropane-1-
carboxylic-acid oxidase. (Adapted from Wimalasekara et al.
2011a
)
(CPA). The tri-amine spd and tetra-amine spm are synthesised by successive ad-
dition of aminopropyl groups to put and spd respectively in reactions catalyzed by
spermidine synthase (SPDS) and spermine synthase (SPMS) (Slocum et al.
1984
;
Tiburcio et al.
1997
). The aminopropyl groups are produced from decarboxylation
of
S
-adenosylmethionine (SAM) catalyzed by SAM decarboxylase (SAMDC) (Slo-
cum et al.
1984
; Tiburcio et al.
1997
) (Fig.
17.1
). The presence of ODC pathway
and characterization of genes coding for ODC is reported from many plant species
(Michael et al.
1996
). However,
Arabidopsis
lacks ODC pathway and biosynthesis
of put occurs exclusively through the ADC pathway (Hanfrey et al.
2001
).
ADC1
and
ADC2
are the two genes that encode ADC of
Arabidopsis
and they are shown
to be expressed in a tissue specific manner (Soyka and Heyer
1999
).
Arabidopsis
has single genes that code for AIH and CPA (Janowitz et al.
2003
; Piotrowski et al.
2003
), two genes namely
SPDS1
and
SPDS2
that code for spermidine synthase
(Panicot et al.
2002
), genes
SPMS
and
ACL5
coding, spermine synthase (Hanzawa
et al.
2000
) and at least four genes coding SAM decarboxylase (Urano et al.
2004
).
In some plant species, subcellular compartmentalization of ADC pathway is re-
ported which probably lead to a concentration gradient of put in a cell (Borrell et al.
1995
; Bortolotti et al.
2004
). A number of studies indicate that genes coding for PA
biosynthesis is highly regulated by an array of abiotic and biotic factors and PA me-
tabolism interacts largely with other metabolic pathways (Bouchereau et al.
1999
;
Soyka and Heyer
1999
; Urano et al.
2003
; Alcázar et al.
2006b
,
2010a
).
Search WWH ::
Custom Search