High Antioxidant Ability Confer Resistance to Atrazine in Commelina communis L.

Asiatic dayflower (Commelina communis L.) is a detrimental weed that mainly infests corn and soybean fields in China. Recently, some C. communis populations have exhibited resistance to atrazine, intensifying the difficulties in controlling the weed. However, little is known on the mechanism underlying C. communis resistance to atrazine. Therefore, two populations collected from Jilin (JL-1) and Jiangsu (JS-10) provinces of China were used to evaluate their growth responses to atrazine. The results showed that the JL-1 population displayed a low level of resistance to atrazine compared with JS-10 population, with the resistant index (RI) value of 2.9. To determine if a mutation in the psbA gene was the basis for varied resistance to this herbicide, the full-length gene encoding 353 amino acids with no intron was sequenced by using genome-walking techniques. No mutation known to confer resistance to atrazine was observed in either JL-1 or JS-10 populations. The malondialdehyde (MDA) contents relative to the control group were significantly higher in JS-10 population than in JL-1 population at 7 days after treatment with atrazine, suggesting that atrazine induced severer oxidant damage on JS-10 population. Additionally, significantly enhanced activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX), were detected in the JL-1 population, which was most likely to confer resistance to atrazine. To the best of our knowledge, this is the first investigation into the potential genetic and enzymatic differences contributing to atrazine resistance in this population.

Molecular characteristic of rbcL and trnH-psbA of Abies delavayi subsp. fansipanensis (Xiang Q.P.) Rurhforth in Vietnam

Abies delavayi subsp. fansipanensis (Xiang Q.P.) Rurhforth) or Abies delavayi var. nukiangensis auct.nonis a native plant, distributes at altitudes about 2,400 m above sea level. This plant belongs to the Pinaceae family and is listed in endangered, precious and rare species banned from commercial exploitation. The Abies delavayi subsp. fansipanensis population in Vietnam only concentrates in a mountainous area at the peak of Fansipan with a population diameter of about 3 km at an altitude of 2,600 to 2,950 m, and is about 500 km far from the Abies delavayi population in Cang Shan (China). In this study, the author sequenced the region of the rbcL and trnH-psbA of Abies delavayi subsp. fansipanensis in Vietnam, compared with the Abies delavayi of China to better understand the genetic characteristics of Abies delavayi subsp. fansipanensis in Vietnam. The results showed that the Abies delavayi subsp. fansipanensis in Vietnam has a different nucleotide position compared to the Chinese Abies nukiangensis at nucleotide no. 455 on the rbcL gene region and two other nucleotide positions in the trnH-psbA genome at positions 332 and 503. The sequences of the rbcL and trnH-psbA gene regions of Abies delavayi subsp. fansipanensis from Vietnam were registered into the GenBank with the accession number MK783132 and MK783131, respectively.

Functional Analysis of PSRP1, the Chloroplast Homolog of a Cyanobacterial Ribosome Hibernation Factor

Bacterial ribosome hibernation factors sequester ribosomes in an inactive state during the stationary phase and in response to stress. The cyanobacterial ribosome hibernation factor LrtA has been suggested to inactivate ribosomes in the dark and to be important for post-stress survival. In this study, we addressed the hypothesis that Plastid Specific Ribosomal Protein 1 (PSRP1), the chloroplast-localized LrtA homolog in plants, contributes to the global repression of chloroplast translation that occurs when plants are shifted from light to dark. We found that the abundance of PSRP1 and its association with ribosomes were similar in the light and the dark. Maize mutants lacking PSRP1 were phenotypically normal under standard laboratory growth conditions. Furthermore, the absence of PSRP1 did not alter the distribution of chloroplast ribosomes among monosomes and polysomes in the light or in the dark, and did not affect the light-regulated synthesis of the chloroplast psbA gene product. These results suggest that PSRP1 does not play a significant role in the regulation of chloroplast translation by light. As such, the physiological driving force for the retention of PSRP1 during chloroplast evolution remains unclear.

NUCLEOTIDE DIVERSITY OF 15 CONIFER SPECIES IN VIETNAM’ S CENTRAL HIGHLANDS BASED ON THE ANALYSIS OF ITS, trnH-psbA, matK, trnL AND rpoC1 GENE REGIONS

In this study, five DNA sequences from ITS, trnH-psbA, matK, trnL and rpoC1 gene regions were used to explore relationships of 15 conifer species in Highlands of Vietnam. All target gene segments has been cloned at size as predicted by the theory for all 15 species of conifers. Nucleotide-level change of 15 coniferous species in five gene regions showed from the highest to the lowest as follows: the ITS gene region (0.428), the trnH-psbA region (0.378), the trnL (0.354), the matK gene (0.192) and the rpoC1 gene (0.105). The matK gene region showed the highest level of conservation (671 nucleotides) and the trnH-psbA gene region showed the lowest (78 nucleotides). Phylogenetic tree showed that the species in the same family are formatted in a separate evolutionary branch with bootstrap values ​​obtained from the branching nodes of each species ranging from 52 to 97% for the ITS gene, from 50 to 100% for trnH-psbA gene region, from 66 to 100% for matK gene region, from 50 to 100% for trnL gene region and from 57 to 100% for rpoC1 gene region. Of the three gene regions of matK, trnL and rpoC1, the grouping of species in the same family showed the most obvious. This result suggests the three gene regions of matK, trnL and rpoC1 could be used as barcode for the 15 conifer species in central highlands of Vietnam.