We have identified a gene that acts in trans to activate the expression of the phenazine biosynthetic genes in the biological control organism Pseudomonas aureofaciens 30-84. This gene, phzR (phenazine regulator), is located upstream of and divergently transcribed from the phenazine biosynthetic genes. Thus, the phenazine biosynthetic locus consists of at least two divergently transcribed operons. A functional phzR gene is required for phenazine production. The nucleotide sequence of phzR revealed an open reading frame of 723 nucleotides encoding a protein of ca. 27 kDa. The predicted amino acid sequence of PhzR has homology with other bacterial positive transcriptional activators, including LasR of Pseudomonas aeruginosa, LuxR of Vibrio fischerii, and TraR of Agrobacterium tumefaciens. The addition of cell-free supernatants from late-exponential-phase cultures of strain 30-84 resulted in expression of a genomic phzB:lacZ reporter strain at a lower cell density than normal, indicating the possible presence of an autoinducer. These results indicate that PhzR is a member of a two-component sensor-regulator family with known or predicted carboxy-terminal DNA-binding domains which regulates gene expression in response to environmental and cell density signals.
To explore the effectiveness of insect derived protease inhibitors in protecting plants against insect feeding, anti-trypsin, anti-chymotrypsin and anti-elastase protease inhibitor (PI) genes from Manduca sexta L. were expressed in transgenic cotton (Gossypium hirsutum L.). From 198 independent transformants, 35 elite lines were further analyzed. Under the control of the 35S promoter of CaMV, PI accumulated to approximately 0.1% of total protein, depending on the tissue analyzed. Using cell-flow cytometry, DNA content/ nuclei of transgenic and non-transformed cotton were identical. On cotton plants expressing PIs, fecundity of Bemisia tabaci (Genn.), the sweetpotato whitefly, was reduced compared to controls. Expression of these protease inhibitors may reduce the developmental rate of B. tabaci and other insects, and provide a strategy for cotton protection.
The blue aleurone trait has been suggested as a useful genetic marker in wheat (Triticum aestivum L.). However, little information is available on its transmission in diverse backgrounds and on its use to identify hybrid seed. UC66049, a hexaploid spring wheat with a spontaneous translocation that included the gene for the blue aleurone trait (Ba) from Agropyron elongatum (Host) P.B. (synonymous with Elytrigia pontica (Podp.) Holub), was crossed to seven wheat cultivars to test the transmission of the trait. UC66049 was crossed to male-sterile red wheat lines to evaluate the blue aleurone trait as a marker for confirming hybridity. Ba segregated as a dominant gene that was transmitted normally through the male and female gametes. For 6 of 7 crosses with diverse pedigrees, we experienced problems with misclassification of the aleurone color in the F2 seed generation, determined by the F3 seed family data. The blue aleurone trait is a good genetic marker; however, progeny testing may be needed to confirm the F2 genotypes in some environments or genetic backgrounds. Moreover, Ba is useful in determining the amount of controlled hybridity as opposed to self-fertility and (or) outcrossing in genetic male-sterile wheat lines. The use of Ba to confirm doubled haploidy was proposed.Key words: Agropyron elongatum, seed color, genetics, Triticum aestivum, Elytrigia pontica.
Four winter wheat (Triticum aestivum L.) and two spring wheat cultivars were evaluated in anther culture on three to four different media for their ability to initiate callus and green plants. Five media were used in the experiment: stored-potato medium with Ficoll 400, fresh-potato medium with Ficoll 400, fresh-t ~tato medium with agar, fresh-potato liquid medium without agar or Ficol1400, and a one tep 85D12-3 medium. Greatly different frequencies of calli and/or green plants were obtained from different cultivars and media. The callus initiation frequency varied from 2.7% for Arapahoe to 52% for Pavon, both on the stored potato medium with Ficoll 400. The frequency of green plant regeneration ranged from 0% for Arapahoe and Siouxland on the stored-potato medium with Ficoll 400 and 0% for Redland and Arapahoe in the fresh-potato medium with Ficoll 400 to 12% for Chris in the 85D12-3 medium (one-step procedure). Chris and Centurk 78, previously reported as having high levels of response, had significantly higher (P < 0.05) frequencies of green plant regeneration on the 85D12-3 medium than the othr-cultivars. An nexpected observation is that 'wet' MSC-medium enhanced callus regeneration mo:-. than a drier MSCmedium.
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