The DapA gene encoding the lysine biosynthetic enzyme dihydrodipicolinate synthase from Coix lacryma-jobi: cloning, characterization, and expression analysis
Ra. Dante et al., The DapA gene encoding the lysine biosynthetic enzyme dihydrodipicolinate synthase from Coix lacryma-jobi: cloning, characterization, and expression analysis, PLANT MOL B, 41(4), 1999, pp. 551-561
Dihydrodipicolinate synthase (DHPS) is the main enzyme of a specific branch
of the aspartate pathway leading to lysine biosynthesis in higher plants.
We have cloned and characterized the DHPS-encoding DapA gene from the maize
-related grass Coix lacryma-jobi. The DapA open reading frame is interrupte
d by two introns and encodes the 326 amino acid-long Coix DHPS protein, whi
ch is 95% identical to the maize DHPS protein. Coix DNA gel blot analysis w
ith maize DHPS cDNA as a probe showed a single strongly hybridizing band al
ong with faint bands. RNA gel blot analysis showed that DHPS transcripts ar
e present in coleoptiles, embryos, endosperms, and roots but are almost und
etectable in blades of young leaves of both Coix and maize. The 5'-flanking
region of the DapA gene contains a TGACTC GCN4-like element located 372 bp
upstream the putative translation start codon. Steady-state levels of DHPS
mRNA were slightly reduced in the endosperms and embryos of the maize lysi
ne-rich opaque2 mutants when compared with those in normal kernels. Selecti
ve binding assay with the maize Opaque2 protein (O2) showed that the GCN4-l
ike element is not an O2 binding site, suggesting that the DHPS gene is not
under the control of O2.