Agriculture Reference
In-Depth Information
The major storage proteins of most cereal grains are glutelin
and prolamin. In rice grains, however, glutelin is the major
protein of the starchy endosperm, constituting at least 80% of
the total protein, prolamin accounting for less than 5%. The
increase in glutelin in the developing rice grain coincide, with
the appearance of Protein body (PB) in the starchy endosperm
7 to 8 DAF and glutelin is found exclusively in PB. In a study it
had been reported that there are two types of PB in the starchy
endosperm of rice grains. One PBI is spherical with a concentric
ring structure, whereas the other PBII is stained homogeneously
by osmium tetraoxide and does not have this structure. PBI
contains prolamin and PBII is rich in glutelin and globulin.
Little, however, is known about the molecular mechanisms
which control the synthesis of the storage proteins of rice seeds.
Studies showed that storage proteins begin to accumulate about
5 days after fl owering. The components of glutelin, the major
storage protein in rice, appeared 5 days after fl owering. Smaller
peptides, including prolamin appeared about 10 days after
fl owering. PBII type protein grows faster than PBI type protein.
Rice grains from 3 varieties and 3 pairs of lines with different
protein content were collected at 4 days intervals from 4 to
32 days after fl owering. Analysis for protein, free amino acid
nitrogen, ribonucleic acid, protease and ribonuclease activities,
in addition, the capacity of the intact grain to incorporate amino
acids showed maximal level of free amino acid nitrogen and
the capacity of the developing grain to incorporate amino acids
were consistently found to be higher with high protein content
grains (Fig. 37). The ribonucleic acid content of the grain also
tended to be higher in high protein grains (Cruz et al. 1970).
The rice with high percentage of protein tended to translocate
more leaf N to the developing grains than the rice with average
grain protein content. The leaf blades of the former had also
