FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
Date
2010-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
JEJU NATIONAL UNIVERSITY
Abstract
hreonine synthase (TS) and dihydrodipicolinate synthase (DHDPS) are enzymes of the
aspartate family pathway leading to biosynthesis of Thr and Lys in plants and
microorganisms, respectively. Sequence analysis of the cDNA of those enzymes from rice
revealed that they harbor a full-length open reading frame for OsTS encoding for 521 amino
acids, corresponding to a protein of approximately 57.2 kDa and OSDHDPS also encoding
for 380 amino acids, corresponding to a protein of approximately 41.4 kDa. The predicted
amino acid sequence of OsTS and OsDHDPS are highly homologous to those of
Arabidopsis and many bacterial respective sequences that are encoded for thrC and dapA
gene, respectively. The OsTS protein harbors a signature binding motif for pyridoxal-5’-
phosphate at the amino terminus. The Os7S expression was complemented by a thrC mutant
strain of E. coli. The OsTS expression was correlated with the survival of the thrC mutant,
which is affected by the supplementation of an Asp pathway metabolite, Met. Expression of
OsDHDPS in dapA mutants of E. coli showed that the gene was able to functionally
complement with the mutant. The result suggested that the OsTS and OsDHDPS encode a
protein TS and DHDPS, respectively in rice.
Description
Rice (Oryza sativa) is a very important crop as the staple food for more than half of
the world’s population. Rice is an ideal model plant among the monocot cereal crop species
for genetic and molecular studies because of its genome compared to those of other cereals,
in additional, its suitable for efficient genetic analysis and transformation (Rakwal and
Agrawal, 2003). Rice is also an important protein source for humans especially in Asian
countries. The demand for rice as a dietary protein source is expected to increase
dramatically in the future since the world population will be doubled by 2030 (Mann, 1997).
Furthermore, to feed the increasing population of the world, it is essential to improve yield
and quality of rice (Khan and Komatsu, 2004). Similar to other cereals, rice seed protein is
deficient in some essential amino acids (Sotelo ef al., 1994).
Keywords
Sequence analysis of OsTS and OSDHDPS, PHILOSOPHY, DOCTOR