DNA methylation of the CDC2L1 gene promoter region decreases the expression of the CDK11p58 protein and reduces apoptosis in keloid fibroblasts.

The excessive growth of fibroblasts in keloid is closely related to the status of gene methylation. The aim of this project was to study whether keloid development is related to DNA methylation in the CDC2L1 gene promoter region. DNA methylation of the promoter of this gene was analyzed by bisulfite sequencing and verified by DNA methylation-specific polymerase chain reaction.

Identification of a TRAP transporter for malonate transport and its expression regulated by GtrA from Sinorhizobium meliloti.

Sinorhizobium meliloti can live as a saprophyte in soil or as a nitrogen-fixing symbiont inside the root nodule cells of alfalfa and related legumes by utilizing different organic compounds as its carbon source. Here we have identified the matPQMAB operon in S. meliloti 1021.

Characterization and expression analysis of Medicago truncatula ROP GTPase family during the early stage of symbiosis.

ROPs (Rho-related GTPases of plants) are small GTPases that are plant-specific signaling proteins. They act as molecular switches in a variety of developmental processes. In this study, seven cDNA clones coding for ROP GTPases have been isolated in Medicago truncatula, and conserved and divergent domains are identified in these predicted MtROP proteins.

Maturation of the nodule-specific transcript MsHSF1c in Medicago sativa may involve interallelic trans-splicing.

In nonplant species, many heat-shock transcription factors (HSFs) undergo spatiotemporal-specific alternative splicing. However, little is known about the spatiotemporal-specific splicing of HSFs in plants. Previously, we reported that the alfalfa HSF gene MsHSF1 undergoes multiple alternative splicing events in various tissues.

Structure and alternative splicing of a heat shock transcription factor gene, MsHSF1, in Medicago sativa.

Plant heat shock transcription factors (HSF) are highly complex. In this study, we identified an alfalfa HSF gene MsHSF1 that is composed of four exons and three introns in the encoding region. The intron1-exon2-intron2-exon3-intron3 as an intervening sequence was inserted at the conserved position that separates the coding region for the DNA-binding domain by single intron in other known plant HSF genes.

Sinorhizobium meliloti nifA mutant induces different gene expression profile from wild type in Alfalfa nodules.

Several studies have demonstrated that the Rhizobium nifA gene is an activator of nitrogen fixation acting in nodule bacteria. To understand the effects of the Sinorhizobium meliloti nifA gene on Alfalfa, the cDNA-AFLP technique was employed to study the changes in gene expression in nifA mutant nodules. Among the approximately 3,000 transcript-derived fragments, 37 had differential expression levels.

[A LuxR family regulator, ExpR regulates the expression of motC operon from Sinorhizobium meliloti].

In Sinorhizobium meliloti strain Rm1021, ExpR+ mutation results in the overproduction of EPS II, which is required for efficient invasion of root nodules on the host plant alfalfa. When rhizobia were grown in LB/MC medium for 36-hour then placed at room temperature, most of ExpR+ mutant (Rm8530) cells aggregated at the bottom of the tubes, but ExpR+ sinR double mutant Rm11528 and wild type Rm1021 did not. The ExpR+ mutant was also found to swim slower than Rm1021 on swarming plates, but the ExpR+ sinR- mutant showed almost the same as wild type.

Two new Sinorhizobium meliloti LysR-type transcriptional regulators required for nodulation.

The establishment of an effective nitrogen-fixing symbiosis between Sinorhizobium meliloti and its legume host alfalfa (Medicago sativa) depends on the timely expression of nodulation genes that are controlled by LysR-type regulators. Ninety putative genes coding for LysR-type transcriptional regulators were identified in the recently sequenced S. meliloti genome.

Role of oxyR from Sinorhizobium meliloti in regulating the expression of catalases.

The process of symbiotic nitrogen fixation results in the generation of reactive oxygen species such as the superoxide anion (O2-) and hydrogen peroxide (H2O2). The response of rhizobia to these toxic oxygen species is an important factor in nodulation and nitrogen fixation. In Sinorhizobium meliloti, one oxyR homologue and three catalase genes, katA, katB, and katC were detected by sequence analysis.

nifH promoter activity is regulated by DNA supercoiling in Sinorhizobium meliloti.

In prokaryotes, DNA supercoiling regulates the expression of many genes; for example, the expression of Klebsiella pneumoniae nifLA operon depends on DNA negative supercoiling in anaerobically grown cells, which indicates that DNA supercoiling might play a role in gene regulation of the anaerobic response. Since the expression of the nifH promoter in Sinorhizobium meliloti is not repressed by oxygen, it is proposed that the status of DNA supercoiling may not affect the expression of the nifH promoter. We tested this hypothesis by analyzing nifH promoter activity in wild-type and gyr- Escherichia coli in the presence and absence of DNA gyrase inhibitors.

Sinorhizobium meliloti ExoR and ExoS proteins regulate both succinoglycan and flagellum production.

The production of the Sinorhizobium meliloti exopolysaccharide, succinoglycan, is required for the formation of infection threads inside root hairs, a critical step during the nodulation of alfalfa (Medicago sativa) by S. meliloti. Two bacterial mutations, exoR95::Tn5 and exoS96::Tn5, resulted in the overproduction of succinoglycan and a reduction in symbiosis.

Improvement of Bacterial Two Hybrid System.

Bacterial two-hybrid system is a newly developed method for studying protein-protein interactions, especially for effects of the environmental factors on the interaction. In our studies of the effect of NH(4)( ) or oxygen on the NifL-NifA interaction, it was found that E.coli strain DHP1 cya(-), when transformed by T18-NifL together with T25-NifA, exhibited high activity of beta-galactosidase in the presence of NH(4)( ), and appeared as red colonies when grown in MacConkey/maltose agar.