Agriculture Reference
In-Depth Information
At low temperature glutamine synthatase and isocitrate
dehydrogenase activities were increased by 80 and 75%
respectively thus a positive parallel correlation was observed
between the two enzymes. Native PAGE analysis, together
with activity staining and Western blot assays, showed that
both GSrb activity and GSrb protein level were enhanced under
low temperature. Meanwhile, NADHGDH and NADGDH
activity were both reduced, though to different extents. At
low temperature, ammonium absorption was stimulated by
the elevation of GS activity. Proline content was increased
twofold by low temperature and this accumulation was in
good agreement with the induction of GS activity. Similar
observations were made in the rice roots fed with sucrose,
indicating that at least partially low temperature has the same
effect as carbon compounds on the modulation of nitrogen
metabolism (Lu et al. 2005).
Polyamines are ubiquitous low molecular weight aliphatic
that are involved in regulation of plant growth and development
(Martin-Tanguy 2001). Because of their polycationic nature
at physiological pH. Polyamines are able to interact with
proteins, nucleic acids, membrane phospholipids and cell wall
constituents, thereby activating or stabilizing these molecules.
The most commonly found polyamines in higher plants, the
diamine putrescine (Put), the triamine spermidine (Spd) and
the tetramine supermidine (Spm) may be present in the free,
soluble, conjugated and insoluble bound forms (Fig. 21).
Cold stress stimulated the phosphorylation of a 60K da
protein in the cold sensitive rice variety IR 36, in an
in vitro
study. However, in the cold tolerant rice variety, Kitaibuki,
this protein had already been phosphorylated (Komatsu and
Kato 1997).
