Zhengsong Peng

Nucleotide diversity and molecular evolution of the WAG-2 gene in common wheat (Triticum aestivum L) and its relatives

In this work, we examined the genetic diversity and evolution of the WAG-2 gene based on new WAG-2 alleles isolated from wheat and its relatives. Only single nucleotide polymorphisms (SNP) and no insertions and deletions (indels) were found in exon sequences of WAG-2 from different species. More SNPs and indels occurred in introns than in exons. For exons, exons+introns and introns, the nucleotide polymorphism π decreased from diploid and tetraploid genotypes to hexaploid genotypes. This finding indicated that the diversity of WAG-2 in diploids was greater than in hexaploids because of the strong selection pressure on the latter. All dn/ds ratios were < 1.0, indicating that WAG-2 belongs to a conserved gene affected by negative selection. Thirty-nine of the 57 particular SNPs and eight of the 10 indels were detected in diploid species. The degree of divergence in intron length among WAG-2 clones and phylogenetic tree topology suggested the existence of three homoeologs in the A, B or D genome of common wheat. Wheat AG-like genes were divided into WAG-1 and WAG-2 clades. The latter clade contained WAG-2, OsMADS3 and ZMM2 genes, indicating functional homoeology among them.

A mathematical model for describing light-response curves in Nicotiana tabacum L.

A modified exponential model was used to describe light-response curves of Nicotiana tabacum L. The accuracies of an exponential model, a nonrectangular hyperbola model, a rectangular hyperbola model, a modified rectangular hyperbola model and the modified exponential model were evaluated by Mean square error (MSE) and Mean absolute error (MAE). The tests MSE and MAE of the modified exponential model were the lowest among the five models. The light saturation point (LSP) obtained by the exponential model, the nonrectangular hyperbola model and the rectangular hyperbola model were much lower than the measured values, and the maximum net photosynthetic rates (Pmax) calculated from these models, were greater than the measured values. Pmax at LSP of 1,077 μmol m−2 s−1 calculated by the modified exponential model was 12.34 μmol(CO2) m−2 s−1, which was more accurate than the values obtained from the modified rectangular hyperbola model. The results show that the modified exponential model is superior to other models for describing light-response curves.

Identification of differentially expressed genes in three-pistil mutation in wheat using annealing control primer system

The common wheat line three-pistil (TP) is a valuable mutant for wheat breeding. The TP mutation has normal spike morphology; however, it only produces three pistils per floret. Therefore, it has potential to increase the grain number per spike. In order to determine the underlying molecular mechanism, an annealing control primer system was used to identify the different expressed genes in three-pistil mutation. Using 120 arbitrary ACP primers, we identified three differentially expressed genes in young spikes between two near-isogenic lines (i.e., Chuanmai 28 TP and Chinese Spring TP) and their recurrent parents. We tentatively designated the three differentially expressed genes as DETP-1, DETP-2, and DETP-3. DETP-1 showed similar function with maize cytoplasmic membrane protein, which is involved in cell division in bacteria. DETP-3 is homologous to maize endo-1, 4-beta-glucanase (EGases), which is associated with plant development, cell wall loosening, stem flowering, and root expansion. DETP-2 showed no significant hit with any sequence found in the database and translates unknown protein. These genes would likely play an important role in determining the three pistils trait in wheat.

Cloning and characterization of endo-β-1,4-glucanase genes in the common wheat line three pistils

In this work, we report the cloning and characterization of endo-β-1,4-glucanase (EGase) genes (TaEG) in the common wheat line three pistils. Three TaEG homoeologous genes (TaEG-4A, TaEG-4B and TaEG-4D) were isolated and found to be located on chromosomes 4AL, 4BS and 4DS, respectively. The three genes showed high conservation of their coding nucleotide sequences and 3 untranslated region. The putative TaEG protein had a molecular mass of 69 kDa, a theoretical pI of 9.39 and a transmembrane domain of 74–96 amino acids in the N-terminus that anchored the protein to the membrane. The genome sequences of TaEG-4A, TaEG-4B and TaEG-4D contained six exons and five introns. All of the introns, except for intron IV, varied in length and sequence composition. Phylogenetic analysis revealed that TaEG was most closely related to rice (Oryza sativa) OsGLU1. The TaEG transcript levels increased significantly during the subsidiary pistil primordium differentiation phase (spike size ∼7–10 mm) in Chuanmai 28 TP (CM28TP). These data provide a basis for future research into the function of TaEG and offer insights into the molecular mechanism of the three pistils mutation in wheat.