Regulation of auxin transport in pea (Pisum sativum L.) by phenylacetic acid: effects on the components of transmembrane transport of indol-3yl-acetic acid

Phenylacetic acid (PAA), a naturally-occurring acidic plant growth substance, was readily taken up by pea (Pisum sativum L. cv. Alderman) stem segments from buffered external solutions by a pH-dependent, non-mediated diffusion. Net uptake from a 0.2 M solution at pH 4.5 proceeded at a constant rate for at least 60 min and, up to approx. 100 M, the rate of uptake was directly proportional to the external concentration of the compound. The net rate of uptake of PAA was not affected by the inclusion of indol-3yl-acetic acid (IAA) in the uptake medium (up to approx. 30 M) and, unlike the net uptake of IAA, was not stimulated by N-1-naphthylphthalamic acid (NPA) or 2,3,5-triiodobenzoic acid. At an external concentration of 0.2 M and pH 4.5, the net rate of uptake of PAA was about twice that of IAA. It was concluded that the uptake of PAA did not involve the participation of carriers and that PAA was not a transported substrate for the carriers involved in the uptake and polar transport of IAA. Nevertheless, the inclusion of 3–100 M unlabelled PAA in the external medium greatly stimulated the uptake by pea stem segments of [1-¹⁴C]IAA (external concentration 0.2 M). It was concluded that whilst PAA was not a transported substrate for the NPA-sensitive IAA efflux carrier, it interacted with this carrier to inhibit IAA efflux from cells. Over the concentration range 3–100 M, PAA progressively reduced the stimulatory effect of NPA on IAA uptake, indicating that PAA also inhibited carrier-mediated uptake of IAA. The consequences of these observations for the regulation of polar auxin transport are discussed.Abbreviations IAA indol-3yl-acetic acid - DMO 5,5-dimethyloxazolidine-2,4-dione - NPA N-1-naphthylphthalamic acid - PAA phenylacetic acid - TIBA 2,3,5-triiodobenzoic acid     

Different routes for integral protein insertion into Ricinus communis protein-body and glyoxysome membranes

Total polyadenylated RNA from ripening or germinating Ricinus communis L. endosperm was translated in rabbit reticulocyte lysate in the absence or presence of canine pancreatic microsomes. The products were immunoprecipitated using antibodies raised againts Triton X-114-extracted integral membrane proteins of protein bodies or glyoxysomes. While the proteins of proteinbody membranes were found to insert co-translationally into added microsomes, this was not observed in the case of glyoxysomal proteins. This observation was confirmed using antibodies raised against a purified glyoxysome membrane protein, alkaline lipase. These results indicate that different routes exist for the insertion of membrane proteins into the two organelles. In both cases membrane-protein insertion does not appear to be accompanied by proteolytic processing.Abbreviations anti-PB antiserum to integral protein-body membrane proteins - anti-G antiserum to integral glyoxysomal membrane proteins - anti-L antiserum to alkaline lipase - ER endoplasmic reticulum - M_r relative molecular mass - mRNA poly(A)-rich messenger RNA - PAGE polyacrylamide gel electrophoresis - poly(A) polyadenylic acid - SDS sodium dodecyl sulphate     

A minority of 46,XX true hermaphrodites are positive for the Y-DNA sequence including SRY

Summary A total of 30 cases of 46,XX true hermaphroditism was analysed for Y-DNA sequences including the recently cloned gene for male testis-determination SRY. In 3 cases, a portion of the Y chromosome including SRY was present and, in 2 cases, was localised, to Xp22 by in situ hybridisation. Since previous studies have shown that the majority of XX males are generated by an X-Y chromosomal interchange, the Xp22 position of the Yp material suggests that certain cases of hermaphroditism can arise by the same meiotic event. The phenotype in the 3 SRY-positive cases may be caused by X-inactivation resulting in somatic mosaicism of testis-determining factor expression giving rise to both testicular and ovarian tissues. Autosomal or X-linked mutation(s) elsewhere in the sex-determining pathway may explain the phenotype observed in the remaining 27 SRY-negative cases.     

Gene expression in nematode-infected plant roots

Summary A major pathogen of potato plants (Solanum tuberosum) is the potato cyst nematode (Globodera spp.), which induces localized redifferentiation of a limited number of host cells to form a specialized feeding-site termed the syncytium. A novel strategy utilizing the polymerase chain reaction (PCR) was employed to construct a cDNA library from dissected potato roots highly enriched in syncytial material. The library was differentially screened with cDNA probes derived from the infected root tissue from a compatible interaction and from healthy root tissue. Characterization of one gene identified by the library screen indicated an expression pattern that correlated with events in the immediate vicinity of the pathogen after syncytial establishment. The strategy for library construction and screening could be applicable to the study of gene expression in any plant-pathogen interaction in which the limited supply of cells at the interface of the two organisms precludes a more traditional approach.     

Idioms of distress: Somatic responses to distress in everyday life

In-depth interviews were conducted among 50 subjects residing in the industrial town of Newcastle, Australia. Half of these subjects were from the general population and half were currently seeking counselling for personal/family problems. None of the subjects were receiving any medical care at the time of interview, though seven had done so during the episode of distress they were discussing. The study shows that while the subjects psychologized their problems, members of both groups tended to somatize at a rate proportional to the level of distress. Subjects were unaware of any relationship between the distress they were experiencing and their physical complaints. The results of this study support previous research which argues that those experiencing distress and those who tend to introspect are also those who are likely to amplify somatic symptoms. At the same time these results depart from findings in the United States which suggest that in the West, people learn to express social and personal distress in psychological terms,, thereby reducing the level of somatization. Though not representative of the population as a whole, the findings raised questions warranting further study.     

Affinity of corticosteroids for mineralocorticoid and glucocorticoid receptors of the rabbit kidney: effect of steroid substitution

Corticosteroid derivatives coupled in the C3, C7 or C17 position with a long aliphatic chain were synthesized in order to select a suitable ligand for the preparation of a biospecific affinity adsorbent for mineralocorticoid receptor purification. The affinity of these derivatives for mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) was explored in rabbit kidney cytosol. In this model, aldosterone bound to a single class of receptors with high affinity (Kd 1 nM) and mineralocorticoid specificity. RU26988, a highly specific ligand for GR, did not compete for these sites. The C7 and C17 positions were found to be of crucial importance in the steroid's interaction with the mineralocorticoid receptors, since the linkage of a long side chain in these positions induced complete loss of affinity. Hence, deoxycorticosterone no longer bound to MR after 17 beta substitution with a 9-carbon aliphatic chain. This loss of affinity was not observed for glucocorticoids. The 17 beta nonylamide derivative of dexamethasone still competed for GR. Increasing the length of the C7 side of the spirolactone SC26304 suppressed its affinity for MR. Finally, C3 was an appropriate position for steroid substitution. The 3-nonylamide of carboxymethyloxime deoxycorticosterone bound to MR but not to GR, and therefore constitutes a suitable ligand for the preparation of a mineralocorticoid adsorbent.     

An X-autosome fusion chromosome of Caenorhabditis elegans

Summary The translocation mnT12(IV;X) is a fusion of holocentric chromosomes IV and X, the breakpoints occurring near the left end of IV and the right end of X. Animals homozygous for mnT12 are viable and fertile; they contain five pairs of chromosomes rather than the normal set of six pairs. The mnT12 chromosome is larger than all wild-type chromosomes and thus identifies linkage groups IV and X cytologically. Hermaphrodites heterozygous for mnT12 show high frequency meiotic nondisjunction both between mnT12 and the X chromosome, which results in a high incidence of male self progeny (27% compared to the wild-type incidence of 0.2%), and between mnT12 and chromosome IV, which results in a high incidence of self progeny essentially trisomic for chromosome IV (karyotype IV/mnT12/mnT12). The viability of chromosome IV trisomics has been confirmed by constructing animals trisomic for only normal copies of chromosome IV; these animals are morphologically wild type. Meiotic chromosome disjunction in mnT12 homozygotes appears to be normal, although the frequency of recombination between markers that are normally X-linked is significantly reduced. Males of genotype IV/mnT12/0 are fertile. They can be thought of as having a neo-X(mnT12) neo-Y(normal IV) karyotype since it is possible to maintain a male-hermaphrodite stock of C. elegans consisting of such males and hermaphrodites carrying two neo-X chromosomes and no neo-Y; the organism is thus converted from an XO:XX type of sex determination to an XX:XX system.     

Vicilin genes ofPisum

Summary We describe four genomic clones of pea 7S storage protein gene, one of which corresponds to convicilin, and the others to vicilin. Hybridization studies exploiting these clones, and previously identified cDNA clones, have enabled us to define six different loci. Three of these loci have been mapped to positions on chromosome 7.