Agriculture Reference
In-Depth Information
Fig. 17.2
Schematic representation of PA catabolic pathways in plants. Copper-binding diamine
oxidases (CuAO)/diamine oxidases ( DAO) catalyses the oxidation of di-amine putrescine, at the
primary amine group producing hydrogen peroxide (H
2
O
2
), ammonia (NH
3
) and 4-aminobutanal
as reaction products. Polyamine oxidase ( PAO) catalyses the oxidation of spermidine and sperm-
ine at the secondary amine group producing 4-aminobutanal and
N
-(3-aminopropyl)-4 aminobu-
tanal respectively, in addition to 1,3-diaminopropane and H
2
O
2
. 4-aminobutanal produced through
putrescine and spermidine oxidation is further converted to γ-aminobutyric acid (GABA) via
Δ
1
-pyrroline. Besides terminal catabolic pathway, back-conversion pathway takes place produc-
ing spermidine and putresine. H
2
O
2
and 3-aminopropanal is produced as reaction products in the
polyamine back conversion pathway. (Modified from Angelini et al.
2010
)
PA-mediated stress tolerance. A number of recent studies indicate that cross talk of
PA signalling with other signalling pathways in a variety of abiotic stress responses
(Alcázar et al.
2010a
).
SaltStress
Plant growth is restricted when the soil contains excess amounts of minerals. Salin-
ity affects a considerable amount of crop loss worldwide specifically in arid and
semiarid regions. Salt injury is caused by decrease in water potential and by accu-
mulation of ions to toxic levels. Tolerance levels to soil salinity differ dramatically
among plant species. The mechanisms by which plants tolerate salinity are complex
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