gal4 transcription activator protein of yeast can function as a repressor in Escherichia coli

The chromosomal lac operator of Escherichia coli was replaced by a 22 bp oligonucleotide containing the binding site of the yeast gal4 protein. Induction of gal4 protein synthesis in these bacteria repressed beta-galactosidase synthesis at least 30-fold. These results show that it is possible to detect in bacteria with a simple assay the DNA binding activity of a eukaryotic protein with a defined sequence specificity. This opens new avenues for the isolation in E. coli of mutants of DNA binding proteins unable to bind to their DNA targets, and for direct cloning in bacteria of cDNA coding for DNA binding proteins with defined sequence specificity.     

ABA is required for Leptosphaeria maculans resistance via ABI1- and ABI4-dependent signaling

Abscisic acid (ABA) is a defense hormone with influence on callose-dependent and -independent resistance against Leptosphaeria maculans acting in the RLMcol pathway. ABA-deficient and -insensitive mutants in Ler-0 background (abal-3 and abil-1) displayed susceptibility to L. maculans, along with a significantly decreased level of callose depositions, whereas abi2-1 and abi3-1 remained resistant, together with the abi5-1 mutant of Ws-0 background. Suppressor mutants of abil-1 confirmed that the L. maculans-susceptible response was due to the dominant negative nature of the abil-1 mutant. Highly induced camalexin levels made ABA mutants in Col-0 background (aba2-1, aba3-1, and abi4-1) appear resistant, but displayed enhanced susceptibility as double mutants with pad3-1, impaired in camalexin biosynthesis. beta-Aminobutyric acid (BABA) pretreatment of Ler-0 contributed to an elevated level of endogenous ABA after L. maculans inoculation. Comparisons between (RLM1co1)pad3 and rlmlLerpad3 showed that ABA and BABA enhancement of callose deposition requires induction from RLM1col. ABII, but not ABI2, was found to be involved in a feedback mechanism that modulates RLM1co, expression. Genetic analysis showed further that this feedback occurs upstream of ABI4 and that components downstream of ABI4 modulate ABIJ activity. ABA and BABA treatments of the L. maculans-susceptible callose synthase mutant pmr4 showed that ABA also induces a callose-independent resistance. Similar treatments enhanced callose depositions and induced resistance to L. maculans in oilseed rape, and BABA-induced resistance was found to be independent of salicylic acid.     

Crystallization of the arginine-dependent repressor/activator AhrC from Bacillus subtilis

The arginine-dependent repressor/activator AhrC from Bacillus subtilis has been crystallized in space group C222(1), with unit cell dimensions a = 229.8 A, b = 72.8 A, c = 137.7 A and one aporepressor hexamer per asymmetric unit. Preliminary X-ray photographs show measurable intensities beyond 3.0 A.     

ABI4调控侧根发育研究(综述)

生长素是调控植物侧根发育的关键植物激素,生长素运输载体PIN蛋白介导其极性分布。ABI4抑制生长素极性运输蛋白基因PIN1的表达,影响生长素的极性运输,抑制侧根形成。本文概述ABI4转录因子调控侧根发育的研究进展。     

4-Thiofuranoid glycals: versatile synthons for stereoselective synthesis of 4'-thionucleosides

Beta-anomers of 4'-thionucleosides have been synthesized stereoselectively, through PhSeCl- or N-iodosuccimide (NIS)-initiated electrophilic glycosidation to 3,5-O-(di-t-butylsilylene)-4-thiofuranoid glycal (1). This synthetic method has been applied to the synthesis of those analogues branched at the anomeric position using 1-C-carbon-substituted 3,5-O-(tetraisopropyldisiloxane-1,3-diyl)-4-thiofuranoid glycals (11-14) prepared based on lithiation of 10.