Over-Expression of a NAD-Malic Enzyme Gene from Rice in Arabidopsis thaliana Confers Tolerances to Several Abiotic Stresses

In order to investigate the role of a rice NAD-malic enzyme gene (OsNAD-ME1) under different abiotic stresses, OsNAD-ME1 was constructed into plant expression vector and transformed into Agrobacterium for infecting Arabidopsis thaliana. There were higher transcriptional levels of OsNAD-ME1 in homozygous transgenic lines compared with WT plants as well as higher NAD-ME activity. WT and transgenic Arabidopsis were treated with NaCl, NaHCO3, mannitol and H2O2. And then their root lengths, crown widths and fresh weights were measured and compared. The results showed that over-expression of OsNAD-ME1 in transgenic Arabidopsis increased the resistance to abiotic stresses, which indicated that OsNAD-ME1 was related to stress tolerance.

Molecular Cloning and Characterization Analysis of Malic Enzyme Gene from Dunaliella parva

Malic enzymes are a class of oxidative decarboxylases which catalyze the oxidative decarboxylation of malate to pyruvate and carbon dioxide. the former studies on lipid pathways and genetic engineering test for enhanced lipid synthesis suggests that ME are the most promising targets gene for enhanced lipid synthesis. The full-length cDNA encoding NADP malic enzyme was obtained from oleaginous microalgae Dunaliella parva, which include 1293 bp open reading frame (ORF) and 26 bp 3′-untranslated sequence. NCBI-CD search revealed that there are two mainly domains predicted in the Dunaliella parva ME protein. In addition, a 724 bp promoter was obtained. The potential regulatory elements associated with hormone and light responses were also found in the ME promoter region. Similarity analysis revealed that the highest identity was found between Dunaliella parva and Chlamydomonas reinhardtii. The Dunaliella parva ME also showed wide similarity with other species.

Transcriptional Regulation of an Iron-Inducible Gene by Differential and Alternate Promoter Entries of Multiple Myb Proteins in the Protozoan Parasite Trichomonas vaginalis

ABSTRACT Iron-inducible transcription of a malic enzyme gene (also reputed to be ap65-1) in Trichomonas vaginalis was previously shown to involve a Myb1 repressor and a Myb2 activator, each of which may preferentially select two closely spaced promoter sites, MRE-1/MRE-2r, which comprises overlapping promoter elements, and MRE-2f. In the present study, an iron-inducible ∼32-kDa Myb3 nuclear protein was demonstrated to bind only the MRE-1 element. Changes in the iron supply, which produced antagonistic effects on the levels of Myb2 and Myb3 expression, also resulted in temporal and alternate entries of Myb2 and Myb3 into the ap65-1 promoter. Repression or activation of basal and iron-inducible ap65-1 transcription was detected in transfected cells when Myb3 was, respectively, substantially knocked down or overexpressed. In the latter case, increased Myb3 promoter entry was detected with concomitant decrease in Myb2 promoter entry under specific conditions, while Myb3 promoter entry was inhibited under all test conditions in cells overexpressing Myb2. In contrast, concomitant promoter entries by Myb2 and Myb3 diminished in cells overexpressing Myb1, except that Myb3 promoter entry was slightly affected under prolonged iron depletion. Together, these results suggest that Myb2 and Myb3 may coactivate basal and iron-inducible ap65-1 transcription against Myb1 through conditional and competitive promoter entries.