Agriculture Reference
In-Depth Information
acids were known to be involved in the changes of protein
concentration (Zhao and Yu 2005). Integrating the previous
reports in wheat and other crops, Xie et al. (2003) concluded
that enhanced ABA contents generally increase protein
concentration, the relationship between the IAA contents
and protein accumulation in grains was negative at the grain
enlargement stage, but positive at the grain fi lling stage and
the effects of enhanced ABA and IAA contents on protein
accumulation were mediated mainly via enhancing mRNA
production and protein gene expression. Thus, grain fi lling
process and protein concentration were infl uenced by changes
of endogenous hormone levels. Application of exogenous GA
3
in grain fi lling stage or even in earlier stage may be benefi cial for
grain fi lling in rice cultivation under low temperature, as low
temperature enhanced ABA concentration, increased protein
content in grain and tends to behave like inferior grains.
Rice grain fi lling is a process of conversion of sucrose into
starch catalyzed by a series of enzymes. Sucrose synthase
(SUS) is considered as a key enzyme regulating this process.
Field grown rice plants and detached cultured panicles under
varying treatments including spikelet thinning, leaf cutting and
application of different concentrations of exogenous sucrose
and ABA during grain fi lling indicates that a higher SUS
activity was found in superior grains than in inferior grains
in the earlier stage of grain fi lling, which was signifi cantly
and closely related to a higher grain fi lling rate and starch
accumulation. An increase in sucrose concentration in grains
as a result of different treatments increased both SUS activity
and SUS protein expression in grains. An increase in ABA
concentration gave similar results. Furthermore, effects of
interactions between sucrose and ABA on the activity and
expression of SUS protein in grains suggests that sucrose and
