Absence of the hemochromatosis gene Cys282Tyr mutation in three ethnic groups from Algeria (Mzab), Ethiopia, and Senegal

 A Celtic origin for hemochromatosis, a common genetic iron metabolism disorder, has been postulated for a long time. To check whether the two mutations recently identified in the HLA-class I candidate gene for this disease were found only in Caucasians, we examined their frequencies in individuals originating from Algeria, Ethiopia, and Senegal. The presumably disease-causing mutation, responsible for the Cys282Tyr substitution, was not found in any member of these ethnic groups, although it was shown to be highly prevalent in populations of European ancestry. This geographic distribution supports the previously suggested Celtic origin for the disease. In contrast, the mutation responsible for the His63Asp substitution is not restricted to European populations. Although absent in the Senegalese, it was found on about 9% of the chromosomes of the Central Ethiopians and Algerians (Mzab) genotyped for this study. This second mutation, which probably represents a common variant unrelated to hemochromatosis, thus appears to have occurred earlier than that responsible for the Cys282Tyr substitution. More detailed population studies are needed to provide information on the age of these two mutations and eventually show how the hemochromatosis-causing mutation chronologically spread throughout Europe. Received: 24 December 1996 / Revised: 11 February 1997     

A new non-HLA multigene family associated with thePERB11 family within theMHC class I region

 In an effort to initiate steps designed to characterize the idiopathic hemochromatosis disease gene, the HLA-A/HLA-F region where this gene is in disequilibrium linkage with some polymorphic markers has been overlapped by a yeast artificial chromosome (YAC) contig. In order to achieve the physical mapping of these YACs and of the corresponding genomic region, we subcloned one of the YACs involved. A computer-assisted analysis of the sequence of one subclone led to the isolation of a potential exon that proved to belong to a new expressed messenger named HCGIX. After Southern blot analysis, the corresponding cDNA clone was found to belong to a new multigene family whose members are dispersed throughout the HLA class I region and are closely associated with members of another recently described multigene family designated PERB11. The data reported here suggest that these two multigene families form a cluster that have been dispersed together throughout the telomeric part of the major histocompatibility complex and have been involved in the genesis of this human class I region. Received: 23 February 1996 / Revised: 23 April 1996     

The ubiquity of natural adsorbable organic halogen production among basidiomycetes

 Recently, several species of basidiomycetes were shown to produce de novo high concentrations of chloroaromatic metabolites. Since these lignocellulose-degrading fungi play a major role in the ecosphere, the purpose of this study was to determine the ubiquity of organohalogen production among basidiomycetes. A total of 191 fungal strains were monitored for adsorbable organic halogen (AOX) production when grown on defined liquid media. Approximately 50% of the strains tested and 55% of the genera tested produced AOX. A low production of 0.1–0.5 mg AOX/l was observed among 25% of the strains, a moderate production of 0.5–5.0 mg AOX/l was observed among 16% of the strains and 9% of the strains produced high levels (5–67 mg AOX/l). The latter group was dominated by species belonging to the genera Hypholoma, Mycena and Bjerkandera, showing specific AOX productions in the range 1074–30893 mg AOX/kg dry weight of mycelial biomass. Many highly ecologically significant fungal species were identified among the moderate to high producers. These species were also able to produce AOX when cultivated on natural lignocellulosic substrates. Hypholoma fasciculare and Mycena metata respectively produced up to 132 mg and 193 mg AOX/kg dry weight of forest litter substrate in 6 weeks. Received: 5 October 1995/Received revision: 28 December 1995/Accepted: 12 February 1996     

Genetic analysis of the dwarfing gene Rht8 in wheat. Part II. The distribution and adaptive significance of allelic variants at the Rht8 locus of wheat as revealed by microsatellite screening

 Wheat microsatellite WMS 261 whose 192-bp allele has been shown to be diagnostic for the commercially important dwarfing gene Rht8 was used to screen over 100 wheat varieties to determine the worldwide spread of Rht8. The results showed Rht8 to be widespread in southern European wheats and to be present in many central European wheats including the Russian varieties ‘Avrora’, ‘Bezostaya’ and ‘Kavkaz’. Rht8 appears to be of importance to South European wheats as alternative giberellic acid (GA)-insensitive dwarfing genes do not appear to be adapted to this environment. The very successful semi-dwarf varieties bred by CIMMYT, Mexico, for distribution worldwide have been thought to carry Rht8 combined with GA-insensitive dwarfing genes. Additional height reduction would have been obtained from pleiotropic effects of the photoperiod-response gene Ppd1 that is essential to the adaptability of varieties bred for growing under short-winter days in tropical and sub-tropical areas. The microsatellite analysis showed that CIMMYT wheats lack Rht8 and carry a WMS 261 allelic variant of 165 bp that has been associated with promoting height. This presumably has adaptive significance in partly counteracting the effects of other dwarfing genes and preventing the plants being too short. Most UK, German and French wheats carry an allelic variant at the WMS 261 locus with 174 bp. This could be selected because of linkage with the recessive photoperiod-sensitive ppd1 allele that is thought to offer adaptive significance northern European wheats. Received: 17 October 1997 / Accepted: 12 November 1997     

Identification and characterization of flavonoids in the root exudate of Robinia pseudoacacia

 Eight compounds exuded from young roots of black locust (Robinia pseudoacacia) were separated by two-dimensional HPTLC, by HPLC and GC, and were identified by spectroscopic methods (ultraviolet/visible spectroscopy and mass spectrometry) as 4′,7-dihydroxyflavone, apigenin, naringenin, chrysoeriol and isoliquiritigenin. Structural assignments were confirmed by comparison with authentic standards. The capacity to induce β-galactosidase activity in Rhizobium sp. NGR234 containing a nod box::lacZ fusion on plasmid pA27 identified these flavonoids and the chalcone as nod gene inducers. This indicates the important role of these compounds in nodulation of this legume tree. Received: 26 July 1996 / Accepted: 9 September 1996     

Recognition by human Vγ9/Vδ2 T cells of melanoma cells upon fusion with Daudi cells

 Daudi Burkitt’s lymphoma cells, unlike other tumor cell lines, stimulate human T cells coexpressing the variable (V) region genes TCRG-V9 and V TCRD-V2 to proliferate and secrete lymphokines. Hybrids, derived by the fusion of Daudi cells with the human melanoma cell line MZ2-MEL 2.2, retain the morphology of melanoma cells. Unlike the parental melanoma cell line, these Daudi × MZ2-MEL 2.2 hybrids stimulate secretion of tumor necrosis factor (TNF) and granulocyte/macrophage colony stimulating factor (GM-CSF) by CD4-positive Vγ9/Vδ2 T-cell clones. Whereas the stimulator phenotype of Daudi cells behaves as a dominant trait in Daudi × melanoma hybrids, the expression of B-cell differentiation markers is suppressed. Thus, the γ/δ T-cell ligand expressed by Daudi cells behaves as a dominant tumor antigen in Daudi × melanoma hybrids and is unrelated to the differentiated B-cell phenotype. Dominant expression of the Daudi ligand for human Vγ9/Vδ2 T cells in these hybrids may provide a basis for defining the stimulatory principle at the molecular level. Received: 2 May 1996 / Revised: 15 July 1996     

Cloning and expression of the α–L-arabinofuranosidase gene (ABF2) of Aspergillus niger in Saccharomyces cerevisiae

 First-strand cDNA was prepared from mRNA of Aspergillus niger MRC11624 induced on oat spelts xylan. Using the cDNA as a template, the α-L-arabinofuranosidase gene (abf B) was amplified with the polymerase chain reaction technique. The abf B DNA fragment was inserted between the yeast phosphoglycerate kinase I gene promoter (PGK1 _P ) and terminator (PGK1 _T ) sequences on a multicopy episomal plasmid. The resulting construct PGK1 _P -abf B-PGK1 _T was designated ABF2. The ABF2 gene was expressed successfully in Saccharomyces cerevisiae and functional α-L-arabinofuranosidase was secreted from the yeast cells. The ABF2 nucleotide sequence was determined and verified to encode a 449-amino-acid protein (Abf 2) that is 94% identical to the α-L-arabinofuranosidase B of A. niger N400. Maximum α-L-arabinofuranosidase activities of 0.020 U/ml and 1.40 U/ml were obtained with autoselective recombinant S. cerevisiae strains when grown for 48 h in synthetic and complex medium respectively. Received: 29 January 1996/Received revision: 3 May 1996/Accepted: 9 May 1996     

Allelic repertoire of the humanMHC class IMICA gene

 The hallmark of the classical major histocompatibility complex (MHC) class I molecules is their astonishing level of polymorphism, a characteristic not shared by the nonclassical MHC class I genes. A distinct family of MHC class I genes has been recently identified within the human MHC class I region. The MICA (MHC class I chain-related A) gene in this family is a highly divergent member of the MHC class I family and has a unique pattern of tissue expression. We have sequenced exons encoding the extracellular α1, α2, and α3 domains of the MICA gene from twenty HLA homozygous typing cell lines and four unrelated individuals. We report the identification of eleven new alleles defined by a total of twenty-two amino acid substitutions. Thus, the total number of MICA alleles is sixteen. Interestingly, a tentative superimposition of MICA variable residues on the HLA-A2 structure reveals a unique pattern of distribution, concentrated primarily on the outer edge of the MICA putative antigen binding cleft, apparently bordering an invariant ligand binding site. Received: 13 May 1996 / Revised: 29 May 1996     

Anti-tyrosinase antibodies in malignant melanoma

 Anti-tyrosinase antibodies were measured by enzyme-linked immunosorbent assay in sera of patients with malignant melanoma with either metastatic disease or no evidence of disease, in patients with melanoma and associated hypopigmentation (MAH), in patients with vitiligo and in healthy volunteers. The mean relative absorbance (A _rel) was calculated by dividing the absorbance of each sample by the mean value for the control group. Using this method, the A _rel of the control group was 1.000(SE 0.083). A _rel of patients with metastatic disease (1.516; SE 0.225) was significantly higher (P = 0.03) than the value for the controls, but insignificantly higher than that for patients with no evidence of disease (1.216; SE 0.148). Patients with no evidence of disease, in whom the primary lesion originated in the lower limb, had a significantly higher (P = 0.01) A _rel than the healthy volunteers. Patients with metastatic disease showed higher A _rel if their primary lesions were confined to the area of the head and neck or to the lower limb. Patients with vitiligo had higher A _rel values for their anti-tyrosinase antibody than any of the other groups. However, those with melanoma and MAH (vitiligo-like) had the same A _rel of anti-tyrosinase antibodies as the controls or the patients with metastatic melanoma. This observation reflected the possible absorption of anti-tyrosinase antibodies to melanoma antigens, and pointed to the participation of anti-tyrosinase antibodies in the destruction of normal melanocytes in patients with melanoma, as part of the immune reaction towards this disease. Received: 4 January 1996 / Accepted: 11 April 1996     

Prognostic markers for survival in patients with metastatic renal cell carcinoma treated with interleukin-2

 Interleukin-2 (IL-2)-based immunotherapy can induce antitumor responses in about 25% of patients with metastatic renal cell carcinoma (RCC). The limited effect and the severe side-effects of IL-2 have led us to perform a prognostic factor analysis. Twenty-four patients with metastatic RCC were treated with IL-2. Flow cytometry and immunohistology were used to determine DNA ploidy, HLA-II expression on tumor cells, and the presence of macrophages in the primary tumor. These variables were examined in relation to survival. The 4-year overall survival rate was 38%. Forty-six percent of the primary tumors were aneuploid. All tumors, except one, showed HLA-II expression and macrophage presence. A statistically significant correlation (r = 0.66, P = 0.002) was found between HLA-II expression and macrophage presence. Patients with high HLA-II expression had a lower 4-year survival (22% compared to 50%), as had patients with high macrophage presence (20% compared to 42%). Of note, patients characterized by both high HLA-II and high macrophage expression had the worst survival (13% compared to 50%). We concluded that DNA ploidy was not predictive for survival, whereas HLA-II expression and macrophage presence may represent valuable prognostic factors related to survival. The present data suggest that more of the patients with no or moderate HLA-II expression and/or no or moderate macrophage presence in the primary tumor could survive with persistance of their malignant disease after having received IL-2 immunotherapy, as compared to patients with both high HLA-II and high macrophage expression. Received: 2 April 1996 / Accepted: 15 October 1996     

A cellulase gene from a new alkalophilic Bacillus sp. (strain N186-1). Its cloning,nucleotide sequence and expression in Escherichia coli

 Several alkalophilic Bacillus spp. strains were selected for their capacity to produce alkaline cellulases. Culture supernatants of these strains showed optimal cellulase activities between pH 8 and 9 and they were stable from pH 6 to pH 12. A cellulase gene (celB1) from the alkalophilic Bacillus sp. strain N186-1 was cloned in Escherichia coli using polymerase chain reaction techniques. The cloned gene was present in a 2.539-bp HindIII fragment and its nucleotide sequence was determined. The coding sequence showed an open-reading frame encoding 389 amino acids. The amino acid sequence, deduced from the nucleotide sequence, permitted us to include it in family 5 (or A) of the glycosyl hydrolases. The complete open-reading frame of celB1 was cloned in the plasmid pET-11d and expressed in E. coli BL21 (DE3), in which a protein of 39 kDa was obtained in the cytoplasm; however, no endoglucanase activity was detected. A second construction in pET-12a allowed the production of a 39-kDa protein located in the periplasmic space of E. coli that had endoglucanase activity. The protein produced has optimal activity at pH 7 and 50°C and it retains more than 70% of its activity after incubation for 1 h at pH 12. Received: 27 December 1995/Received revision: 14 March 1996/Accepted: 25 March 1996     

Use of an industrial effluent as a carbon source for denitrification of a high-strength wastewater

Denitrification of a high-strength synthetic wastewater (150 g NO^- ₃ l^-1) was carried out using a wine distillery effluent as an example of an industrial carbon source (22.7 g chemical oxygen demand l^-1). Two configurations were tested: one consisted of an acidogenesis reactor followed by a denitrifying reactor and the other was a single reactor directly fed with the raw effluents. In both cases, denitrification was achieved at a nitrate load of 9.54 g NO^- ₃ l^-1 day^-1 (2.19 g N as NO^- ₃ l^-1 day^-1) with good specific reduction rates: 32.6 mg and 35.2 mg N as NO _x  g volatile suspended solids h^-1, calculated on a single day, for the two-step and the one-step process respectively. Dissimilatory nitrate reduction to ammonium did not occur, even in the one-step process. Received: 26 October 1995/Received revision: 15 February 1996/Accepted: 20 February 1996     

A high-resolution map of the regulator of the complement activation gene cluster on 1q32 that integrates new genes and markers

 Sixteen microsatellite markers, including two described here, were used to construct a high-resolution map of the 1q32 region encompassing the regulator of the complement activation (RCA) gene cluster. The RCA genes are a group of related genes coding for plasma and membrane associated proteins that collectively control activation of the complement component C3. We provide here the location of two new genes within the RCA gene cluster. These genes are PFKFB2 that maps 15 kilobases (kb) upstream of the C4BPB gene, and a gene located 4 kb downstream of C4BP A, which seems to code for the 72 000 M _r component of the signal recognition particle (SRP72). Neither of these two genes is related structurally or functionally to the RCA genes. In addition, our map shows the centromere-telomere orientation of the C4BPB/MCP linkage group, which is: centromere-PFKFB2-C4BPB-C4BPA-SRP72-C4BPAL1-C4BPAL2-telomere, and outlines an interval with a significant female-male recombination difference which suggests the presence of a female-specific hotspot(s) of recombination. Received: 12 December 1996 / Revised: 23 December 1996     

The genes encoding light-harvesting subunits of Cyclotella cryptica (Bacillariophyceae) constitute a complex and heterogeneous family

Total RNA was isolated from the diatom Cyclotella cryptica and separated into poly(A)⁺ and poly(A)⁻ fractions. These fractions were subjected to in vitro translation/immunoprecipitation experiments using an antiserum directed against the predominant light-harvesting complex of Cy. cryptica (ccry antiserum) and a heterologous antiserum raised against the light-harvesting complex of the cryptophyte Cryptomonas maculata (cmac antiserum). From translation reactions programmed with poly(A)⁺ RNA the ccry-antiserum immunoprecipitated polypeptides with relative molecular weights (Mr) of 27 000, 25 000, 23 000 and 21 000, while the cmac-antiserum precipitated proteins with Mrs of 32 500 and 27 000, respectively. Subsequent cDNA synthesis and immunological screening of the cDNA library with both antisera resulted in the isolation of six cDNA clones encoding light-harvesting subunits. Full-length precursors were 199-210 amino acids in length and had Mrs of 20 000–23 000. The lengths of the putative signal peptides were 29 or 30 amino acids. Pairwise comparison revealed that the similarity between the clones ranged from 54–99% on the nucleotide level and from 36–99% at the amino acid level. In agreement with the data from the screens with the two antisera, the genes clustered into two groups. The data provide evidence that the genes constitute a heterogeneous multigene family and that the light-harvesting system of Cy. cryptica might be as complex as that of higher plants and green algae. Received: 23 March 1998 / Accepted: 25 July 1998     

Isolation of mutants of Penicillium purpurogenum resistant to catabolite repression

 The strain Penicillium purpurogenum P-26 was subjected to UV irradiation and N-methyl-N′-nitro-N-nitrosoguanidine treatment and mutants were isolated capable of synthesizing cellulase under the conditions of a high concentration of glucose. Initially mutants resistant to catabolite repression by 2-deoxy-D-glucose were isolated on Walseth’s cellulose/agar plates containing 15–45 mM 2-deoxy-D-glucose. These mutants were again screened for resistance to catabolite repression by glycerol or glucose on Walseth’s cellulose/agar plates containing 50 g/l glycerol or 50 g/l glucose respectively. Four mutants with different sizes of clearing zone on Walseth’s cellulose/agar plates containing 50 g/l glucose were selected for flask culture. Among them, the mutant NTUV-45-4 showed better carboxymethylcellulase activity in flask culture containing 1% Avicel plus 3% glucose than did the parental strain. Received: 9 October 1995/Received revision: 27 November 1995/Accepted: 8 January 1996     

Characterization of a high-affinity monoclonal antibody specific for CD44v6 as candidate for immunotherapy of squamous cell carcinomas

 Variant isoforms of CD44, a family of cell-surface glycoproteins generated by alternative splicing and post-translational modifications, are expressed in a variety of human tumors and play important roles in tumor progression and metastasis formation. The murine monoclonal IgG1 antibody VFF18, specific for an epitope encoded by human CD44 variant exon 6, binds with high affinity to the recombinant protein (K _d = 1.7×10^–10 M) as well as to tumor cell lines in vitro, and is suitable for immunohistochemical analysis of human tumors. Screening of more than 500 tumor samples of different histogenesis showed that VFF18 most strongly and uniformly reacts with squamous cell carcinomas (SCC). Detailed analysis of 185 SCC (head and neck, lung, skin) confirmed reactivity of the antibody with 99% of the samples, with intense and homogeneous staining of the tumor cells in the majority of cases, whereas reactivity of VFF18 with normal tissues is limited to certain epithelia and activated lymphocytes. When radiolabelled VFF18 was administered to nude mice bearing human epidermoid carcinoma (A-431) xenograft, fast and selective tumor uptake of the radioimmunoconjugate with a maximum of 18% of the injected dose per gram of tissue was observed. Taken together, these data suggest that mAb VFF18 is a promising targeting vehicle for radioimmunotherapy of squamous cell carcinomas in humans. Received: 9 September 1996 / Accepted: 25 September 1996     

Allele-specific expression of the mouse B-cell surface protein CD72 on T cells

 CD72 is a 45 000 M _r mouse B-cell surface glycoprotein involved in B-cell proliferation and differentiation. Expression of mouse CD72 is thought to be restricted to the B-cell lineage. We recently demonstrated that the monoclonal antibodies K10.6 and B9.689, previously defined as recognizing the mouse lymphocyte alloantigens Ly-19.2 and Ly-32.2, respectively, recognize specific alleles of CD72. Early studies using antibody-mediated cytotoxicity assays demonstrated that K10.6 and B9.689 react with B cells, several T-cell lines, and a subset of peripheral T cells. These findings led us to consider the possibility that CD72 might also be expressed on a subset of T cells. In this report we demonstrate that CD72 is constitutively expressed on a fraction of peripheral T cells isolated from strains of mice expressing the CD72 ^b allele, but not the CD72 ^a or CD72 ^c alleles. Three days after activating T cells with concanavalin A or plate-bound CD3-specific mAb, CD72 is expressed on a larger fraction of peripheral T cells as well as a fraction of thymocytes from mouse strains expressing the CD72 ^b allele. CD72 is expressed on both the CD4⁺ and CD8⁺ thymocyte and peripheral T-cell subsets. No CD72 expression is detected on activated thymocytes or peripheral T cells from mouse strains expressing the CD72 ^a or CD72 ^c alleles. Expression of CD72 ^b on peripheral T cells was confirmed by northern blot analysis demonstrating CD72 mRNA expression. These results demonstrate that CD72 expression is not restricted to B lineage cells in mouse strains expressing the CD72 ^b allele; instead, a population of T lineage cells in these mice also expresses CD72. Received: 18 June 1996 / Revised: 17 September 1996     

Isolation of Mhc class I cDNAs from the axolotl Ambystoma mexicanum

 Class I major histocompatibility complex (Mhc) cDNA clones were isolated from axolotl mRNA by polymerase chain reaction (PCR) and by screening a cDNA phage library. The nucleotide and predicted amino acid sequences show definite similarities to the Mhc class Iα molecules of higher vertebrates. Most of the amino acids in the peptide binding region that dock peptides at their N and C termini in mammals are conserved. Several amino acids considered to be important for the interaction of β₂-microglobulin with the Mhc α chain are also conserved in the axolotl sequence. The fact that axolotl class I A cDNAs are ubiquitously expressed and highly polymorphic in the α1 and α2 domains suggests the classical nature of axolotl class I A genes. Received: 3 June 1996 / Revised: 14 October 1996     

Immunochemotherapy of malignant glioma: synergistic activity of CD95 ligand and chemotherapeutics

 Malignant glioma cells are susceptible to CD95(Fas/APO-1)-mediated apoptosis triggered by agonistic antibody. Here we examined the proapoptotic effects of the natural CD95 ligand, a cytotoxic cytokine homologous to tumor necrosis factor, on malignant glioma cell lines LN-229, LN-308 and T98G. We assessed whether glioma cell killing is synergistically enhanced by cotreatment with CD95 ligand and chemotherapeutic agents, including doxorubicin, carmustine, vincristine, etoposide, teniposide, 5-fluorouracil and cytarabine. Synergy was examined at low concentrations of cytotoxic drugs and CD95 ligand with a defined effect level (IC₁₅). Short-term-cytotoxicity assays showed prominent killing of the glioma cells by CD95 ligand but not by the drugs at relevant concentrations. CD95 ligand-induced apoptosis in the acute toxicity paradigm was augmented by doxorubicin and vincristine. Growth-inhibition assays revealed prominent synergy between CD95 ligand and all drugs examined. The best synergy was obtained with CD95 ligand and doxorubicin, vincristine or teniposide. The strong synergistic antiproliferative effects were observed at much lower concentrations of CD95 ligand and cytotoxic drugs than the moderate synergistic acute cytotoxic effects. All cell lines examined express the Bcl-2 protein. LN-229 has partial wild-type p53 activity. T98G has mutant p53. LN-308 has a deleted p53 gene and lacks p53 protein expression. Thus, synergistic effects of CD95 ligand and cytotoxic drugs were observed in cell lines exhibiting two features thought to play a role in the chemoresistance of human malignant glioma cells: loss of wild-type p53 activity and acquisition of bcl-2 expression. Ectopic expression of murine bcl-2 conferred partial protection from CD95 ligand and drugs when administered alone but did not interfere with the mechanisms underlying the synergistic effects of CD95 ligand and chemotherapeutic drugs. Received: 31 October 1996 / Accepted: 4 January 1997     

Effects of increasing saturation vapour pressure deficit on growth and ABA levels in black spruce and jack pine

 Plant responses to saturation vapour pressure deficit (SVPD) were studied by subjecting black spruce [Picea mariana (Mill) B.S.P.] and jack pine seedlings (Pinus banksiana Lamb.) to humid (0.3 – 0.8 kPa) or dry (2.0 – 2.5 kPa SVPD) regimes for 4 weeks using a computer-controlled environmental system to control diurnal variation in SVPD. Dry matter accumulation in needles was not altered by increasing SVPD. However, root growth declined by 60% which increased shoot to root ratio and reduced total seedling dry weight in both black spruce and jack pine. Relative growth rate of jack pine also declined to about half the rate of plants grown under humid conditions. In situ root marking studies showed that the decline in root growth of jack pine under the high SVPD was the result of reduced lateral root initiation, whereas root elongation was unaffected by humidity. A 4-week exposure to dry air increased abscisic acid (ABA) levels in needles, but not roots, of jack pine whereas ABA levels in black spruce were not altered. A short (3-day) exposure failed to increase needle ABA levels in either species. These results suggest that the responses of conifers to dry air were not the result of ABA accumulation. Received: 24 March 1996 / Accepted: 30 May 1996