Heterologous expression of the AtDREB1A gene in chrysanthemum increases drought and salt stress tolerance

DNA cassette containing an AtDREB1A cDNA and a nos terminator, driven by a cauliflower mosaic 35S promoter, or a stress-inducible rd29A promoter, was transformed into the ground cover chrysanthemum (Dendranthema grandiflorum) ‘Fall Color’ genome. Compared with wild type plants, severe growth retardation was observed in 35S:DREB1A plants, but not in rd29A:DREB1A plants. RT-PCR analysis revealed that, under stress conditions, the DREB1A gene was over-expressed constitutively in 35S:DREB1A plants, but was over-expressed inductively in rd29A:DREB1A plants. The transgenic plants exhibited tolerance to drought and salt stress, and the tolerance was significantly stronger in rd29A:DREB1A plants than in 35S:DREB1A plants. Proline content and SOD activity were increased inductively in rd29A:DREB1A plants than in 35S:DREB1A plants under stress conditions. These results indicate that heterologous AtDREB1A can confer drought and salt tolerance in transgenic chrysanthemum, and improvement of the stress tolerance may be related to enhancement of proline content and SOD activity.     

AtDREB1A基因在菊花中的异源表达提高了植株对干旱和盐渍胁迫的耐性

将携带有AtDREB1A基因, 并以35S或rd29A启动子驱动的植物表达载体转入地被菊花(Dendranthema grandiflorum)的粉色品种‘Fall color’. 与野生型相比, 35S:DREB1A转基因植株表现出严重的生长抑制, 而rd29A:DREB1A植株生长正常. RT-PCR检测表明, 在胁迫条件下, AtDREB1A基因在35S: DREB1A转基因植株中呈现组成型过量表达, 而在rd29A:DREB1A植株中则是受胁迫诱导型过量表达. 这两种启动子驱动的转基因植株对干旱和盐渍胁迫都表现出较强的耐性, 其中rd29A:DREB1A植株耐性显著强于35S:DREB1A植株. rd29A:DREB1A植株中的脯氨酸含量和SOD活性都强烈地被胁迫诱导升高, 且高于35S:DREB1A植株. 这些结果表明, 在地被菊花中表达AtDREB1A基因可以提高植株对干旱和盐渍胁迫的耐性, 同时这些耐性的升高可能与脯氨酸含量和SOD活性的上升有关.     

Antisense suppression of proline degradation improves tolerance to freezing and salinity in Arabidopsis thaliana

The location of tryptophan residues in the actin macromolecule was studied on the basis of the known 3D structure. For every tryptophan residue the polarity and packing density of their microenvironments were evaluated. To estimate the accessibility of the tryptophan residues to the solvent molecules it was proposed to analyze the radial dependence of the packing density of atoms in the macromolecule about the geometric center of the indole rings of the tryptophan residues. The proposed analysis revealed that the microenvironment of tryptophan residues Trp-340 and Trp-356 has a very high density. So these residues can be regarded as internal and inaccessible to solvent molecules. Their microenvironment is mainly formed by non-polar groups of protein. Though the packing density of the Trp-86 microenvironment is lower, this tryptophan residue is apparently also inaccessible to solvent molecules, as it is located in the inner region of macromolecule. Tryptophan residue Trp-79 is external and accessible to the solvent. All residues that can affect tryptophan fluorescence were revealed. It was found that in the close vicinity of tryptophan residues Trp-79 and Trp-86 there are a number of sulfur atoms of cysteine and methionine residues that are known to be effective quenchers of tryptophan fluorescence. The most essential is the location of SG atom of Cys-10 near the NE1 atom of the indole ring of tryptophan residue Trp-86. On the basis of microenvironment analysis of these tryptophan residues and the evaluation of energy transfer between them it was concluded that the contribution of tryptophan residues Trp-79 and Trp-86 must be low. Intrinsic fluorescence of actin must be mainly determined by two other tryptophan residues--Trp-340 and Trp-356. It is possible that the unstrained conformation of tryptophan residue Trp-340 and the existence of aromatic rings of tyrosine and phenylalanine and proline residues in the microenvironments of tryptophan residues Trp-340 and Trp-356 are also essential to their blue fluorescence spectrum.     

Functional analysis of the 37 kDa inner envelope membrane polypeptide in chloroplast biogenesis using a Ds-tagged Arabidopsis pale-green mutant

To study the functions of the nuclear genes involved in chloroplast development, we systematically analyzed albino and pale-green Arabidopsis thaliana mutants by using a two-component transposon system based on the Ac/Ds element of maize as a mutagen. One of the pale-green mutants, albino or pale green mutant 1 (designated as apg1), did not survive beyond the seedling stage, when germinated on soil. The chloroplasts of the apg1 plants contained decreased numbers of lamellae with reduced levels of chlorophyll. A gene encoding a 37 kDa polypeptide precursor of the chloroplast inner envelope membrane was disrupted by insertion of the Ds transposon in apg1. The 37 kDa protein had partial sequence similarity to the S-adenosylmethionine-dependent methyltransferase. The apg1 plants lacked plastoquinone (PQ), suggesting that the APG1 protein is involved in the methylation step of PQ biosynthesis, which is localized at the envelope membrane. Our results demonstrate the importance of the 37 kDa protein of the chloroplast inner envelope membrane for chloroplast development in Arabidopsis.     

Identification of a gene family (kat) encoding kinesin-like proteins in Arabidopsis thaliana and the characterization of secondary structure of KatA

A gene family, designated kat, has been characterized in Arabidopsis thaliana by genomic Southern hybridization and nucleotide sequencing analysis. The kat gene family includes at least five members, named katA, katB, katC, katD and katE, whose products share appreciable sequence similarities in their presumptive ATP-binding and microtubule-binding motifs with known kinesin-like proteins. The carboxyl-terminal region of the KatA protein deduced from the nucleotide sequence of the cDNA clone has considerable homology with the mechanochemical motor domain of the kinesin heavy chain. The predicted secondary structure of the KatA protein indicates two globular domains separated by a long a helical coiled coil with heptad repeat structures, such as are commonly found in kinesin-like proteins.