Involvement of Carrot Cell Surface Proteins in Attachment of Agrobacterium tumefaciens

The initial step in tumor formation by Agrobacterium tumefaciens is the site-specific attachment of the bacteria to plant cells. A similar attachment to plant tissue culture cells has been observed. Binding to carrot suspension culture cells was not dependent on the presence of divalent cations and was not inhibited by the addition of mannose, α-methyl mannoside, galactose, arabinose, glucosamine, 2-deoxyglucose, or 0.25 molar NaCl to the culture medium. The ability of the carrot cells to bind A. tumefaciens was markedly reduced by elution of the cells with dilute detergent or CaCl₂ or by incubation of the cells with proteolytic enzymes. The carrot cells were not killed by these treatments and recovered the ability to bind A. tumefaciens within 3 to 6 hours. A. tumefaciens did not bind to carrot cells which had been induced to form embryos (AG Matthysse, RHG Gurlitz 1982 Physiol Plant Pathol 21: 381-387). A comparison of the peptides eluted from embryos and from uninduced cells using sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that there were several changes in extractable polypeptides after embryo induction. One or more of the polypeptides present before embryo induction and absent from embryos may be involved in the binding of A. tumefaciens to the carrot cell surface.     

Identification of somatic hybrids in plant protoplast fusions with monoclonal antibodies to plasma-membrane antigens

Monoclonal antibodies generated by immunization with a plasma-membrane preparation from suspension-cultured cells of Nicotiana glutinosa L. were used in combination with fluoresceinor rhodamine-labeled goat anti-mouse immunoglobulins to identify heterokaryons in protoplast fusion procedures. Antibody labeling did not inhibit callus formation nor plantlet regeneration. The antibodies are non-invasive and surface labeling provides clear optical discrimination of true heterokaryons from unfused aggregates as well as from parental protoplasts and homokaryons. Labeling is stable throughout fusion and hence by pre-labeling parental protoplast populations the strategy is both versatile and of general applicability.     

Mutational analysis of the Bradyrhizobium japonicum common nod genes and further nod box-linked genomic DNA regions

Summary By insertional and deletional marker replacement mutagenesis the common nod region of Bradyrhizobium japonicum was examined for the presence of additional, essential nodulation genes. An open reading frame located in the 800 bp large intergenic region between nodD1 and nodA did not appear to be essential for nodulation of soybean. Furthermore, a strain with a deletion of the nodI- and nodJ-like genes downstream of nodC had a Nod⁺ phenotype. A mutant with a 1.7 kb deletion immediately downstream of nodD1 considerably delayed the onset of nodulation. This region carried a second copy of nodD (nodD2). A nodD1-nodD2 double mutant had a similar phenotype to the nodD2 mutant. Using a 22-mer oligonucleotide probe partially identical to the nod box sequence, a total of six hybridizing regions were identified in B. japonicum genomic DNA and isolated from a cosmid library. Sequencing of the hybridizing regions revealed that at least three of them represented true nod box sequences whereas the others showed considerable deviations from the consensus sequence. One of the three nod box sequences was the one known to be associated with nodA, whereas the other two were located 60 to 70 kb away from nif cluster I. A deletion of one of these two sequences plus adjacent DNA material mmutant 308) led to a reduced nodulation on Vigna radiata but not on soybean. Thus, this region is probably involved in the determination of host specificity.Dedicated to Prof. Giorgio Semenza on the occasion of his 60th birthday     

Two mRNAs that differ by two nontemplated nucleotides encode the amino coterminal proteins P and V of the paramyxovirus SV5

The "P" gene of the paramyxovirus SV5 encodes two known proteins, P (Mr approximately equal to 44,000) and V (Mr approximately equal to 24,000). The complete nucleotide sequence of the "P" gene has been obtained and is found to contain two open reading frames, neither of which is large enough to encode the P protein. We have shown that the P and V proteins are translated from two mRNAs that differ by the presence of two nontemplated G residues in the P mRNA. These two additional nucleotides convert the two open reading frames to one of 392 amino acids. The P and V proteins are amino coterminal and have 164 amino acids in common. The unique C terminus of V consists of a cysteine-rich region that resembles a cysteine-rich metal binding domain. An open reading frame that contains this cysteine-rich region exists in all other paramyxovirus "P" gene sequences examined, which suggests that it may have important biological significance.     

Fertility of the early postpartum, lactating domestic rabbit

Sixty-four crossbred primiparous lactating does each suckling six pups were allocated at random into four groups and were mated on either Day 1, 2, 3, or 4 post partum (where Day 0 = the day of parturition). They were subsequently killed on Day 10 post coitum (where Day 0 = the day of mating) to assess fertility. There were no significant differences between treatment groups in their mating response (97% overall), ovulation response (77% overall), implantation response (83% overall), implantation rate (8.7 overall), or preimplantation mortality rate (24% overall). Ovulation rate was significantly increased in does mated on Days 3 and 4 (13.3 and 13.1, respectively), compared with those mated on Day 1 (10.2, P<0.05) and Day 2 (9.6, P<0.01) post partum. From these results we conclude that fertility is high throughout the early postpartum period in the lactating rabbit.     

Molecular organisation of the quinic acid utilization (QUT) gene cluster in Aspergillus nidulans

Summary The functional integrity of the QUTB gene (encoding quinate dehydrogenase) has been confirmed by transformation of a qutB mutant strain. The DNA sequence of the contiguous genes QUTD (quinate permease), QUTB and QUTG (function unknown) has been determined and analysed, together with that of QUTE (catabolic 3-dehydroquinase). The QUTB sequence shows significant homology with the shikimate dehydrogenase function of the complex AROM locus of Aspergillus nidulans, and with the QA-3 quinate dehydrogenase and QA-1S (repressor) genes of Neurospora crassa. The QUTD gene shows strong homology with the N. crassa QA-Y gene and QUTG with the QA-X gene. QUTD, QUTB, and QUTG, QUTE form two pairs of divergently transcribed genes, and conserved sequence motifs identified in the two common 5 non-coding regions show significant homology with UAS _GAL and UAS _QA sequences of the Saccharomyces cerevisiae and N. crassa Gal and QA systems. In addition, conserved 5 sequences homologous to the mammalian CAAT box are noted and a previously unreported conserved 22 nucleotide motif is presented.     

A second gene (qutH) within the Aspergillus nidulans-quinic-acid utilisation gene cluster encodes a protein with a putative zinc-cluster motif.

A sequence of 3299 nt, contiguous with the previously sequenced quinate permease-encoding (qutD) gene and encompassing the dehydroshikimate dehydratase-encoding (qutC) gene, has been determined. Northern-blot analysis detected (i) a quinate-inducible mRNA of the expected size for the qutC gene, and (ii) a quinate-inducible mRNA of 1.45 kb divergently transcribed away from qutC towards qutD. Computer-aided sequence analysis identified an ORF of 1047 nt corresponding to the qutC gene encoding dehydroshikimate dehydratase. In addition, a genetically uncharacterized 1188-nt gene, designated qutH and containing a putative intron of 61 nt, was identified between qutC and qutD. The inferred protein sequence encoded by qutH contains a putative 'zinc cluster' motif and has a low (16%) but significant similarity with the DNA-directed DNA polymerase of hepatitis B virus. The results are interpreted as being consistent with the view that the qutH gene encodes a DNA-binding protein, possibly involved in the regulation of genes essential for the utilisation of protocatechuic acid.