Carbohydrate Metabolism in Rice Tissue Culture

Plant cells possess totipotency that
means whole plants could be
regenerated from single cell by
modulating culture conditions. The
mechanisms of totipotency, however,
were limitedly understood so far. The
purpose of this project is to explore the
possible roles of carbohydrate
metabolism in osmotic-stressed rice
callus during shoot regeneration. After
thorough studies, we already got good
understanding of the changes of soluble
sugars, starch, and the enzymes related
to sugar and starch metabolisms. From
the other study in our lab, it had found the contents of endogenous IAA and
ABA were increased significantly in rice
callus by osmotic stress treatment, and
were correlated to the ability of shoot
regeneration. We, therefore, did
further studies to explore the correlation
among phytohormones, carbohydrate
metabolism and osmotic stress during
shoot regeneration.
Two Kinds of callus were used in the
studies. TN5 callus was induced on
MSD10 basal medium and used as
control. TN5-AnA callus was induced
on MSD10 basal medium containing
2mM anthranilic acid and 100μM ABA.
The results showed that during callus
induction stage, TN5-AnA callus has
lower callus growth rate, cellular water
content, water potential, and osmotic
potential than TN5 callus. After being
transferred to regeneration medium,
TN5-AnA showed prosperous shoot
regeneration. Besides, both soluble
sugars and starch contents are
prominently higher in TN5-AnA callus.
All these phenomenon in TN5-AnA
callus are similar to those in osmoticstressed
callus. It proved that the
osmotic stress could be replaced with the
treatment of exogenous phytohormones
to induce shoot regeneration feature.
Therefore, we proposed that osmotic
stress might affect the contents of
endogenous IAA and ABA which serve
as signals to regulate carbohydrate
metabolism, and finally cause the shoot
regeneration of rice callus.