Comparative expression of miRNA genes and miRNA-based AFLP marker analysis in cultivated tetraploid cottons

MicroRNAs (miRNAs) are a class of small non-coding RNAs that down-regulate gene expression in a sequence specific manner to control plant growth and development. The identification and characterization of miRNAs are critical steps in finding their target genes and elucidating their functions. The objective of the present study was to assess the genetic variation of miRNA genes through expression comparisons and miRNA-based AFLP marker analysis. Seven miRNAs were first selected for RT-PCR and four for quantitative RT-PCR analysis that showed considerably high or differential expression levels in early stages of boll development. Except for miR160a, differential gene expression of miR171, 390a, and 396a was detected in early developing bolls at one or more timepoints between two cultivated cotton cultivars, Pima Phy 76 (Gossypium barbadense) and Acala 1517-99 (Gossypium hirsutum). Our further work demonstrated that genetic diversity of miRNA genes can be assessed by miRNA-AFLP analysis using primers designed from 22 conserved miRNA genes in combination with AFLP primers. Homologous miRNA genes can be also identified and isolated for sequencing and confirmation using this homology-based genotyping approach. This strategy offers an alternative to isolating a full length of miRNA genes and their up-stream and down-stream sequences. The significance of the expression and sequence differences of miRNAs between cotton species or genotypes needs further studies.     

胞质雄性不育白菜叶绿体ndhJ-trnF区域序列发生变异

以来自Polima胞质甘蓝型油菜雄性不育源转育获得的不育白菜'Bpol97-05A'和其回交亲本即保持系'Bajh97-01B'为材料,利用cDNA扩增片段长度多态性(cDNA-AFLP)技术获得一条长约330bp的特异片段P1708,RT-PCR验证确认该序列为不育白菜材料所特有,经测序和BLAST比对,发现该片段除54bp的插入序列外,其余部分与大白菜和甘蓝叶绿体ndhJ-trnF基因之间的一段序列完全一致.根据基因区域两端的保守部位设计引物,以Polima不育白菜DNA和可育甘蓝型油菜的DNA为模板,分别获得了长约1900bp的序列,比较序列发现:不育白菜与可育白菜、甘蓝型油菜的DNA序列存在一定差异,'Bpol97-05A'中除多个位点发生变异外,另有108bp的插入序列,该插入由2个长度为54bp的重复序列组成,重复序列中除5′端3个碱基CTT外,其余部分均与trnF基因3′端51bp完全相同.     

胞质雄性不育白菜叶绿体ndhJ-trnF区域序列发生变异

以来自Polima胞质甘蓝型油菜雄性不育源转育获得的不育白菜‘Bpol97-05A’和其回交亲本即保持系‘Bajh97-01B’为材料，利用cDNA扩增片段长度多态性(cDNA-AFLP)技术获得一条长约330 bp的特异片段P1708，RT-PCR验证确认该序列为不育白菜材料所特有，经测序和BLAST比对，发现该片段除54 bp的插入序列外，其余部分与大白菜和甘蓝叶绿体ndhJ-trnF基因之间的一段序列完全一致. 根据基因区域两端的保守部位设计引物，以Polima不育白菜DNA和可育甘蓝型油菜的DNA为模板，分别获得了长约1 900 bp的序列，比较序列发现：不育白菜与可育白菜、甘蓝型油菜的DNA序列存在一定差异，‘Bpol97-05A’中除多个位点发生变异外，另有108 bp的插入序列，该插入由2个长度为54 bp的重复序列组成，重复序列中除5′端3个碱基CTT外，其余部分均与trnF基因3′端51 bp完全相同.     

Chibby functions in Xenopus ciliary assembly,embryonic development,and the regulation of gene expression

Wnt signaling and ciliogenesis are core features of embryonic development in a range of metazoans. Chibby (Cby), a basal-body associated protein, regulates β-catenin-mediated Wnt signaling in the mouse but not Drosophila. Here we present an analysis of Cby?s embryonic expression and morphant phenotypes in Xenopus laevis. Cby RNA is supplied maternally, negatively regulated by Snail2 but not Twist1, preferentially expressed in the neuroectoderm, and regulates β-catenin-mediated gene expression. Reducing Cby levels reduced the density of multiciliated cells, the number of basal bodies per multiciliated cell, and the numbers of neural tube primary cilia; it also led to abnormal development of the neural crest, central nervous system, and pronephros, all defects that were rescued by a Cby-GFP chimera. Reduction of Cby led to an increase in Wnt8a and decreases in Gli2, Gli3, and Shh RNA levels. Many, but not all, morphant phenotypes were significantly reversed by the Wnt inhibitor SFRP2. These observations extend our understanding of Cby?s role in mediating the network of interactions between ciliogenesis, signaling systems and tissue patterning.     

Isolation and characterization of a cDNA encoding a serine proteinase from the root-knot nematode Meloidogyne incognita

This report describes the first serine proteinase gene isolated from the sedentary nematode Meloidogyne incognita. Using degenerate primers, a 1372bp cDNA encoding a chymotrypsin-like serine proteinase (Mi-ser1) was amplified from total RNA of adult females by RT-PCR and 5' and 3' rapid amplification of cDNA ends. The deduced amino acid sequence of Mi-ser1 encoded a putative signal peptide and a prodomain of 22 and 33 amino acids, respectively, and a mature proteinase of 341 amino acids with a predicted molecular mass of 37,680Da. Sequence identity with the top serine proteinases matches from the databases ranged from 23 to 27%, including sequences from insects, mammals, and other nematodes. Southern blot analysis suggested that Mi-ser1 is encoded by a single or few gene copies. The pattern of developmental expression analyzed by Northern blot and RT-PCR indicated that Mi-ser1 was transcribed mainly in females. The domain architecture composed of a single chymotrypsin-like catalytic domain and the detection of a putative signal peptide suggested a digestive role for Mi-ser1.     

Identification of active VQ motif-containing genes and the expression patterns under low nitrogen treatment in soybean

Plant VQ motif-containing protein family plays crucial roles in plant growth, seed development, and defense responses in Arabidopsis. However, its function in soybean is still not well defined. We aim to identify the VQ gene family, and explore the genetic variation of active GmVQ genes in soybean and their expression patterns under low nitrogen stresses. A total of 74 VQ motif-containing genes were identified in soybean genome, and were clustered into five distinct subfamilies (GmVQI–V) with each gene having two or three copies except GmVQ55 (GmVQIV) with single copy. Fourteen genes with relatively high expression level, at least in one tissue, were defined as active GmVQ genes. Most of these active GmVQ genes specifically expressed in soybean pod shell (7/74), root (9/74) and/or nodule (10/74) respectively. Single nucleotide polymorphism (SNP) analysis in cultivated and wild soybeans revealed there were selected site(s) in GmVQ6, GmVQ7, GmVQ10, GmVQ26 and GmVQ61, which means that these genes have undergone artificial selection during soybean domestication. After low nitrogen treatment, enhanced expression of VQ genes was noticed in specific tissues, such as GmVQ53, GmVQ26, GmVQ58, GmVQ61, GmVQ70 and GmVQ6 in shoot, and GmVQ53, GmVQ58, GmVQ48 in root. On the contrary, suppressed expression of GmVQ57, GmVQ21 and GmVQ1 genes was noticed in root after the treatment. Duplicated copy of the active GmVQ genes showed similar expression pattern, suggesting that these genes might be complete copies. The results suggested that soybean VQ-motif containing genes may act as positive or negative regulators in soybean growth, development and nitrogen metabolism. Taken together, our results provided useful information for functional characterization of soybean GmVQ genes to unravel their biological roles.     

Methylenetetrahydrofolate reductase 677TT genotype might be associated with an increased lung cancer risk in Asians

Background

The association between methylenetetrahydrofolate reductase (MTHFR) 677C > T polymorphism and lung cancer risk has been studied in various populations with conflicting results. The aim of this study was to assess the association strength by a meta-analysis of published studies.

Methods

We searched PubMed and Chinese Biomedical (CBM) databases for relevant literatures published by July 18, 2012. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated to assess the strength of the association.

Results

A total of 20 studies comprising 11,653 cases and 12,032 controls were included in the final meta-analysis. Using the random effect model, we found that MTHFR 677TT variant genotype was associated with an increased lung cancer risk (OR = 1.26, 95% CI = 1.05–1.50, P = 0.011 for TT vs. CC; OR = 1.19, 95% CI = 1.03–1.37, P < 0.001 for TT vs. CC + CT; OR = 1.11, 95% CI = 1.02–1.22, P = 0.017 for T allele vs. C allele). In the further stratified analyses, the increased lung cancer risk was found in Asian subjects (OR = 1.31, 95% CI = 1.01–1.71, P = 0.045 for TT vs. CC; OR = 1.17, 95% CI = 1.00–1.38, P = 0.048 for TT vs. CC + CT). There were no evidences for obvious publication bias in the overall meta-analysis and Asian subjects.

Conclusions

MTHFR 677TT genotype might increase the susceptibility of lung cancer, especially in Asians.     

Heat shock protein 70 is required for tabtoxinine-β-lactam-induced cell death in Nicotiana benthamiana

Tabtoxinine-β-lactam (TβL), a non-specific bacterial toxin, is produced by Pseudomonas syringae pv. tabaci, the causal agent of tobacco wildfire disease. TβL causes death of plant cells through the inhibition of glutamine synthetase, which leads to an abnormal accumulation of ammonium ions and the characteristic necrotic wildfire lesions. To better understand the mechanisms involved in TβL-induced cell death, we studied its regulation in Nicotiana benthamiana. TβL-induced lesions, similar to those in controls, could be observed in SGT1-, RAR1- and Hsp90-silenced plants. In contrast, Hsp70-silenced plants showed suppression of lesion formation. Expression of hin1, a marker gene for the hypersensitive response (HR), which is a characteristic of programmed cell death in plants, was strongly induced in controls by TβL treatment but only slightly in Hsp70-silenced plants. However, in these TβL-treated Hsp70-silenced plants, the amount of ammonium ions was considerably increased. Furthermore, the silencing of Hsp70 also suppressed l-methionine sulfoximine-induced cell death and hin1 expression and caused the over-accumulation of ammonium ions. When inoculated directly with P. syringae pv. tabaci, Hsp70-silenced plants showed only reduced symptoms. Our results suggest that the TβL-induced pathway to cell death in N. benthamiana is at least partially similar to HR response, and that Hsp70 might play an essential role in these events.     

Identification and mRNA expression profile of glutamate receptor-like gene in quinclorac-resistant and susceptible Echinochloa crus-galli

Animal ionotropic glutamate receptors (iGluRs) function as Ca^2 + ion channels during excitatory neurotransmission in nerve cells. Here, a glutamate receptor-like gene (GLR) was identified and characterized from a plant — Echinochloa crus-galli. The GLR gene was designated EcGLR1 with GenBank no: JX518597. It has a 2793 bp open reading frame predicted to encode a 101.7 kDa protein. Sequence alignment showed that EcGLR1 is a GLR homologue. Its expression in response to quinclorac treatment was assessed by real-time PCR in near-isogenic lines of quinclorac-resistant (R) and susceptible (S) biotypes of E. crus-galli. The expression of EcGLR1 in the seedling leaf and root at least increased 5 times in the S plants and 22 times in the R plants after exposure to quinclorac. In the adult plant leaves, roots and stems, its expression increased 11–14 times in the S plants and 23–25 times in the R plants after quinclorac stimulation. In the seed, its expression was 4 times less in the S plants than that in the R plants, but after treatment, the levels all increased by about 24 times in the two biotypes. EcGLR1 expression was 1–4 times greater in the R plants than in that in the S plants, and after treatment by quinclorac, the difference increased to a ratio of 4 to 9. Its expression was higher in all tissues tested of R biotypes than in that of S plants before or after quinclorac treatment. The results of this study provide basic information for the further research of function of the EcGLR1 in resistance to quinclorac in E. crus-galli.