Anchored reference loci in loblolly pine (Pinus taeda L.) for integrating pine genomics.

Anchored reference loci provide a framework for comparative mapping. They are landmarks to denote conserved chromosomal segments, allowing the synthesis of genetic maps from multiple sources. We evaluated 90 expressed sequence tag polymorphisms (ESTPs) from loblolly pine (Pinus taeda L.) for this function. Primer sets were assayed for amplification and polymorphism in six pedigrees, representing two subgenera of Pinus and a distant member of the Pinaceae, Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco). On average, 89% of primer sets amplified in four species of subgenus Pinus, 49% in one species of subgenus Strobus, and 22% in Douglas-fir. Polymorphisms were detected for 37-61% of the ESTPs within each pedigree. Comparative mapping in loblolly and slash pine (P. elliottii Englm.) revealed that ESTPs mapped to the same location. Disrupted synteny or significant disruptions in colinearity were not detected. Thirty-five ESTPs met criteria established for anchor loci. The majority of those that did not meet these criteria were excluded when map location was known in only a single species. Anchor loci provide a unifying tool for the community, facilitating the creation of a "generic" pine map and serving as a foundation for studies on genome organization and evolution.

Enhanced production of insecticidal proteins in Bacillus thuringiensis strains carrying an additional crystal protein gene in their chromosomes.

A two-step procedure was used to place a cryIC crystal protein gene from Bacillus thuringiensis subsp. aizawai into the chromosomes of two B. thuringiensis subsp. kurstaki strains containing multiple crystal protein genes. The B. thuringiensis aizawai cryIC gene, which encodes an insecticidal protein highly specific to Spodoptera exigua (beet armyworm), has not been found in any B. thuringiensis subsp. kurstaki strains. The cryIC gene was cloned into an integration vector which contained a B. thuringiensis chromosomal fragment encoding a phosphatidylinositol-specific phospholipase C, allowing the B. thuringiensis subsp. aizawai cryIC to be targeted to the homologous region of the B. thuringiensis subsp. kurstaki chromosome. First, to minimize the possibility of homologous recombination between cryIC and the resident crystal protein genes, B. thuringiensis subsp. kurstaki HD73, which contained only one crystal gene, was chosen as a recipient and transformed by electroporation. Second, a generalized transducing bacteriophage, CP-51, was used to transfer the integrated cryIC gene from HD73 to two other B. thuringiensis subsp. kurstaki stains. The integrated cryIC gene was expressed at a significant level in all three host strains, and the expression of cryIC did not appear to reduce the expression of the endogenous crystal protein genes. Because of the newly acquired ability to produce the CryIC protein, the recombinant strains showed a higher level of activity against S. exigua than did the parent strains. This two-step procedure should therefore be generally useful for the introduction of an additional crystal protein gene into B. thuringiensis strains which have multiple crystal protein genes and which show a low level of transformation efficiency.

Cloning of a novel cryIC-type gene from a strain of Bacillus thuringiensis subsp. galleriae.

A novel cryIC-type gene was isolated from a strain of Bacillus thuringiensis subsp. galleriae. A new polymerase chain reaction (PCR) technique with a set of several oligonucleotide primer pairs specific to the cryIC gene was used to screen a number of B. thuringiensis strains. PCR amplified several DNA fragments ranging from 100 bp to 1 kb for B. thuringiensis strains containing a cryIC gene. PCR fragments amplified from the Bacillus thuringiensis subsp. galleriae HD29 DNA differed from the fragments amplified from other cryIC-containing strains, indicating strain HD29 contained a novel cryIC-type gene. To isolate crystal genes homologous to cryIC, an HD29 gene library was probed with a 984-bp fragment of the amino-terminal coding region of the cryIC gene cloned from Bacillus thuringiensis subsp. aizawai HD229. A putative toxin gene was isolated from a phage that hybridized strongly to the cryIC probe. Translation of the putative toxin DNA sequence revealed an open reading frame of 1,176 amino acids whose predicted molecular mass was 132.8 kDa. Comparisons of the toxin gene sequence with sequences of other cry genes indicated that this gene is a subclass of cryIC. We propose to designate this gene cryIC(b). In Escherichia coli, the cryIC(b) gene produced a protein of approximately 130 kDa toxic to Spodoptera exigua and Trichoplusia ni.

Isolation of tobacco SSU genes: characterization of a transcriptionally active pseudogene.

Genomic clones containing three genes for the small subunit (SSU) of ribulose bisphosphate carboxylase were isolated from tobacco. Detailed analysis was performed on two of these clones to give a clearer picture of this multigene family in tobacco. This analysis demonstrated that one of the clones contained a pseudogene that was unusual in that it was transcriptionally active. This is the first transcriptionally active pseudogene that has been reported in plants. In addition, another clone was found to contain coding sequences which are 100% homologous to a previously-cloned tobacco SSU gene (Mazur, B.J. and Chiu, C-F. [1985] Nuc. Acids Res. 13, 2372-2386), indicating that gene duplication and/or gene conversion may have played a role in the evolution of the tobacco SSU family.