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Objective: To study the association of single nucleotide polymorphisms (SNPs) of transcription factors (NKX2.5, GATA4, TBX5, and FOG2) with congenital heart disease (CHD) in the Chinese population., Methods: PubMed, Google Scholar, CNKI, Wanfang Data, and Weipu Data were searched for articles on the association of SNPs of target genes with CHD in the Chinese population. If one locus was mentioned in at least two articles, the random or fixed effect model was used to perform a pooled analysis of study results and to calculate the pooled OR and its 95%CI. If a locus was mentioned in only one article, related data were extracted from this article to analyze the association between the SNPs of this locus and CHD., Results: Twenty-three articles were included. The Meta analysis showed that there were significant differences between the CHD and control groups in the genotype and allele frequencies of GATA4 rs1139244 and rs867858 and the genotype frequency of GATA4 rs904018, while there were no significant differences in the SNPs of the other genetic loci between the two groups. The single-article analysis showed that there were significant differences between the two groups in the allele frequencies of NKX2.5 rs118026695/rs703752, GATA4 rs884662/rs12825/rs12458/rs3203358/rs4841588, and TBX5 rs6489956. There were no significant differences in the SNPs of FOG2 locus between the two groups., Conclusions: The SNPs of some loci in NKX2.5, GATA4, and TBX5 are associated with CHD in the Chinese population, but the association between the SNPs of FOG2 locus and the development of CHD has not been found yet.

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. Within this operon, matP, matQ and the M region of the fused gene matMA encode an extracytoplasmic solute receptor, a small transmembrane protein and a large transmembrane protein, consisting of three components of the tripartite ATP-independent periplasmic (TRAP) transporter for malonate transport. The A region of the fused gene matMA and matB encode malonate-metabolizing enzymes, malonyl-CoA decarboxylase and malonyl-CoA synthetase. The null mutant of each matPQMAB gene is unable to grow on M9 minimal medium containing malonate as the sole carbon source. However, these mutants can induce the formation of efficient nitrogen-fixing root nodules on alfalfa. The matPQMAB operon is expressed in free-living bacterial cells and symbiotic bacterial cells from infection threads and root nodules. The GntR family transcriptional regulator, GtrA, specifically binds the promoter of the matPQMAB operon, positively regulating its expression. Moreover, the matPQMAB can be transcriptionally induced by malonate. These results suggested that a C(3)-dicarboxylic acid TRAP transporter is responsible for malonate transport in S. meliloti., (Copyright 2010 Elsevier Masson SAS. All rights reserved.)

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. Here, we identified another spliced transcript isoform, MsHSF1c, containing a 177-base tandem repeat, and showed that the low-abundance MsHSF1c is a nodule-specific transcript of MsHSF1. We also found that MsHSF1 presents multiple alleles with single-base variations and the expression of MsHSF1 alleles has allele-specific differences in alfalfa nodules. Because single-base variations at position 1006 change the AT of MsHSF1b to GT in MsHSF1b-3, creating a pair of donor/acceptor sites with the AG of MsHSF1b/1b-1 at position 827-828 for pre-mRNA splicing, we suggest that MsHSF1c may be generated by trans-splicing between alleles MsHSF1b-3 and MsHSF1b or MsHSF1b-1. These results provide new insight into the role of tissue-specific contribution in the transcription of plant HSF genes.

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. Alternative splicing of MsHSF1 has generated five transcript isoforms. Spliced transcript MsHSF1b consisted of exon1 and exon4, encodes a class A1 HSF protein that can specifically bind to the heat shock elements in vitro. Other four spliced transcripts (MsHSF1a-1 to 4) consist of exon1, part of the intervening sequence and exon4. These transcripts carry the premature termination codon and are low-abundant. Apparently these transcripts are the targets of nonsense-mediated mRNA decay (NMD). These results provide new insight into roles in the expression regulation of plant HSF genes.

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. These expression levels were subsequently confirmed by reverse Northern blot and RT-polymerase chain reaction. Sequence analyses revealed that 21 cDNA fragments corresponded to genes involved in signal communication, protein degradation, nutrient metabolism, cell growth and development.

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. All 90 putative lysR genes were mutagenized using plasmid insertions as a first step toward determining their roles in symbiosis. Two new LysR-type symbiosis regulator genes, lsrA and lsrB, were identified in the screening. Both the lsrA and lsrB genes are expressed in free-living S. meliloti cells, but they are not required for cell growth. An lsrA1 mutant was defective in symbiosis and elicited only white nodules that exhibited no nitrogenase activity. Cells of the lsrA1 mutant were recovered from the white nodules, suggesting that the lsrA1 mutant was blocked early in nodulation. An lsrB1 mutant was deficient in symbiosis and elicited a mixture of pink and white nodules on alfalfa plants. These plants exhibited lower overall nitrogenase activity than plants inoculated with the wild-type strain, which is consistent with the fact that most of the alfalfa plants inoculated with the lsrB1 mutant were short and yellow. Cells of the lsrB1 mutant were recovered from both pink and white nodules, suggesting that lsrB1 mutants could be blocked at multiple points during nodulation. The identification of two new LysR-type symbiosis transcriptional regulators provides two new avenues for understanding the complex S. meliloti-alfalfa interactions which occur during symbiosis.

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. This oxyR gene is located next to and divergently from katA on the chromosome. To investigate the possible roles of oxyR in regulating the expression of catalases at the transcriptional level in S. meliloti, an insertion mutant of this gene was constructed. The mutant was more sensitive and less adaptive to H2O2 than the wild type strain, and total catalase/peroxidase activity was reduced approximately fourfold with the OxyR mutation relative to controls. The activities of KatA and KatB and the expression of katA::lacZ and katB::lacZ promoter fusions were increased in the mutant strain compared with the parental strain grown in the absence of H2O2, indicating that katA and katB are repressed by OxyR. However, when exposed to H2O2, katA expression was also increased in both S. meliloti and Escherichia coli. When exposed to H2O2, OxyR is converted from a reduced to an oxidized form in E. coli. We concluded that the reduced form of OxyR functions as a repressor of katA and katB expression. Thus, in the presence of H2O2, reduced OxyR is converted to the oxidized form of OxyR that then results in increased katA expression. We further showed that oxyR expression is autoregulated via negative feedback.