A killer factor produced by the cellular slime mold Polysphondylium pallidum

A killer strain was discovered in cellular slime molds. The wild isolate CK-8 of Polysphondylium pallidum kills all other strains in Polysphondylium and Dictyostelium, as far as could be determined, except strain CK-8 itself and its complementary mating type strain CK-9. Growth-phase cells of CK-8 excrete a killer factor which is sensitive to heat, above 60°C for 5 min, and trypsin. The apparent molecular mass of the factor was determined at 10 000–12 000.Abbreviations BSS Bonner's salt solution - CM conditioned medium     

刺激大鼠下丘脑室旁核激活的中脑中央灰质神经元对躯体传入的反应

电刺激大鼠下丘脑室旁核(PVH),在同侧中脑中央灰质(CG)内寻找逆行及顺行反应单位,然后观察它们对躯体感觉刺激的反应。实验结果表明:CG 及邻近网状结构内有10%(32/318)的单位呈逆行反应。逆行传导速度平均为0.37±0.24m/s(均数±标准差);推测这种CG→PVH 投射纤维属于细有髓或无髓神经纤维。这些单位分布于 CG 的腹外侧及背外侧亚核。50%(14/28)的逆行单位对坐骨(胫)神经的强电刺激和夹尾等损伤性刺激起反应,但对触毛或低强度的神经干刺激无明显反应。以上结果表明:外周躯体感觉,特别是损伤性信息传入 PVH 时,CG 是其中枢驿站之一。电刺激 PVH 还能顺行激活7.55(24/318)、抑制0.7%(2/318)的 CG 单位。有69%(18/26)的顺行反应单位对外周躯体神经强电刺激及夹尾起反应。提示 PVH 可能通过影响 CG神经元的活动而参与中枢痛觉的整合。     

Silver ions inhibit the ethylene-stimulated production of ripening-related mRNAs in tomato

Abstract. Silver ions effectively inhibited both the initiation and the continuation of tomato ( Lyeopersicon esculentum Mill) ripening. Studies of protein synthesis in vivo showed that application of 2 mol m⁻³ silver thiosulphate to mature green fruit prevented the appearance of several novel proteins associated with ripening, including the softening enzyme polygalacturonase. However, total protein synthesis, as judged by the incorporation of [³⁵S] methionine into proteins, continued unabated after silver treatment. Ripening was also arrested when silver was supplied after ripening had begun. The accumulation of several ripening-related mRNAs, including that for polygalacturonase, was studied by translation in vitro and using cDNA clones as hybridization probes. Silver was shown to prevent the appearance of polygalaturonase mRNA when supplied to mature green fruit and to cause a rapid reduction in the concentration of mRNA for polygalacturonase and other ripening-related proteins when supplied after ripening had begun. It is proposed that silver exerts its effects due to interaction with the ethylene perception mechanism. The results suggest that perception of ethylene is vital not only for the initiation of ripening but also for the continued expression of genes required for ripening.     

Relationship between the population of viable sclerotia ofSclerotium rolfsii in soil to cropping sequence in the Nigerian savanna

Populations of viable sclerotia ofSclerotium rolfsii were highest in soil in a field in which tomato was planted for three successive years before sampling and in one in which tomato followed groundnut in the 2 years prior to this study. The lowest sclerotial numbers were recorded in fields in which groundnut followed maize or in which maize or sorghum was the last crop before sampling.     

Immunocytochemical localization of cytokinins in Craigella tomato and a sideshootless mutant

Post-embedding immunocytochemical techniques using peroxidase-antiperoxidase or immunoglobulin G-gold as markers were used for the localization of cytokinins (CKs) in two isogenic lines, Craigella (C) and Craigella lateral suppressor (Cls), of tomato Lycopersicon esculentum Mill. Terminal buds, nodes, hypocotyl segments and root tips were submitted to a periodate-borohydride procedure, to obtain the coupling of isopentenyladeosine and zeatin riboside to cellular proteins, followed by a fixative step with a paraformaldehyde and glutaraldehyde mixture. Enzyme-linked immunosorbent assay tests performed on ovalbumin-coated microtitration plates have shown that this method was effective for CK riboside and base coupling to proteins. Paraffin-wax- or Spurr's-resin-embedded sections were cleared of wax or resin before incubation with anti-zeatin riboside or anti-isopentenyladenosine antibodies. The procedure was thoroughly investigated and many controls were done in order to eliminate artefacts. The immunostaining patterns observed along the plants showed a basipetally decreasing gradient of CKs along the stem and in the roots. Immunolabelling was higher in the actively growing regions of the stem bud and root apices. Terminal buds of Cls appeared to be less immunoreactive than C, whereas no differences were detected in root-tip immunolabelling. The staining patterns are consistent with the idea that root and bud apices have a different CK metabolism. The absence of axillary bud formation in Cls is correlated with low CK levels in the organogensis sites.Abbreviations C Craigella, isogenic line - CK cytokinin - Cls Craigella lateral suppressor - EDC 1-(3-dimethylaminopropyl)3-ethylcarbodiimide hydrochloride - ELISA enzyme-linked immunosorbent assay - 2iP isopentenyladenine - 2iPA isopentenyladenosine - PAP peroxidase-anti-peroxidase - PFAG paraformaldehyde/glutaraldehyde mixture - Z zeatin - ZR zeatin riboside     

Effect of nitrogen stress and abscisic acid on nitrate absorption and transport in barley and tomato

The potential of barley (Hordeum vulgare L.) and tomato (Lycopersicon esculentum Mill.) roots for net NO ₃ ^- absorption increased two-to five fold within 2 d of being deprived of NO ₃ ^- supply. Nitrogen-starved barley roots continued to maintain a high potential for NO ₃ ^- absorption, whereas NO ₃ ^- absorption by tomato roots declined below control levels after 10 d of N starvation. When placed in a 0.2 mM NO ₃ ^- solution, roots of both species transported more NO ₃ ^- and total solutes to the xylem after 2 d of N starvation than did N-sufficient controls. However, replenishment of root NO ₃ ^- stores took precedence over NO ₃ ^- transport to the xylem. Consequently, as N stress became more severe, transport of NO ₃ ^- and total solutes to the xylem declined, relative to controls. Nitrogen stress caused an increase in hydraulic conductance (L _p) and exudate volume (J _v) in barley but decrased these parameters in tomato. Nitrogen stress had no significant effect upon abscisic acid (ABA) levels in roots of barley or flacca (a low-ABA mutant) tomato, but prevented an agerelated decline in ABA in wild-type tomato roots. Applied ABA had the same effect upon barley and upon the wild type and flacca tomatoes: L _p and J _v were increased, but NO ₃ ^- absorption and NO ₃ ^- flux to the xylem were either unaffected or sometimes inhibited. We conclude that ABA is not directly involved in the normal changes in NO ₃ ^- absorption and transport that occur with N stress in barley and tomato, because (1) the root ABA level was either unaffected by N stress (barley and flacca tomato) or changed, after the greatest changes in NO ₃ ^- absorption and transport and L _p had been observed (wild-type tomato); (2) changes in NO ₃ ^- absorption/transport characteristics either did not respond to applied ABA, or, if they did, they changed in the direction opposite to that predicted from changes in root ABA with N stress; and (3) the flacca tomato (which produces very little ABA in response to N stress) responded to N stress with very similar changes in NO ₃ ^- transport to those observed in the wild type.Abbreviation and symbols ABA abscisic acid - J_v exudate volume - L_p root hydraulic conductance     

Acid phosphatase-11, a tightly linked molecular marker for root-knot nematode resistance in tomato: from protein to gene,using PCR and degenerate primers containing deoxyinosine

With a view to cloning the root-knot nematode resistance gene Mi in tomato by chromosome walking, we have developed a molecular probe for the tightly linked acid phosphatase-1 (Aps-1) locus. The acid phosphatase-1 allozyme (APS-1¹), encoded by the Aps-1 ¹ allele originating from Lycopersicon peruvianum, was purified to apparent homogeneity from tomato roots and suspension cells. Microsequencing of CNBr and tryptic peptides generated from APS-1¹ provided a partial amino acid sequence, which accounted for approximately 23% of the protein and revealed two stretches of homology with soybean proteins KSH3 and VSP27, comprising 22 matches within 26 amino acid residues. The partial amino acid sequence information enabled us to isolate a 2.4 kb genomic Aps-1 ¹ sequence by means of the polymerase chain reaction (PCR), primed by degenerate pools of oligodeoxyribonucleotides, synthesized on the basis of the amino acid sequences. Synthesis of the 2.4 kb PCR product was specific for genomic templates carrying the L. peruvianum Aps-1 ¹ allele. Crucial to the priming specificity and the synthesis of the 2.4 kb genomic sequence was the use of degenerate primer pools in which the number of different primer species was limited by incorporating deoxyinosine phosphate residues at three and four base ambiguities. In using cDNA as a template, a 490 bp sequence was obtained, indicating a high proportion of intron sequences in the 2.4 kb genomic Aps-1 ¹ sequence. The Aps-1 ¹ origin of the PCR product was confirmed by RFLP (restriction fragment length polymorphism) analysis, using both a chromosome 6 substitution line and a pair of nearly isogenic lines, differing for a small chromosomal region around the Aps-1/Mi loci.     

Biosynthesis and degradation of α-tomatine in developing tomato fruits

Fruits of tomato incorporated [2-¹⁴C]mevalonic acid lactone into the steroidal glycoalkaloid α-tomatine. Young fruits showed the greatest alkaloid-synthesizing ability but this decreased as the fruits developed. Analysis of sap exuded from fruit stalks and also application of[4-¹⁴C]cholesterol to leaves confirmed that tomatine is not transported into fruits from vegetative organs. Accumulation of this alkaloid in fruits thus appears entirely due to synthesis. Excised fruits of all developmental stages degraded injected [¹⁴C]tomatine and rates were directly related to fruit age. The pattern of accumulation/decline in fruit tomatine may be explicable on the basis of changing capacity for synthesis/degradation during development. Label from injected [¹⁴C]tomatine was present mainly in chlorophylls and carotenoids where it increased with time as that in tomatine decreased. The significance of the relationship between tomatine disappearance and carotenoid development is briefly discussed. The aglycone tomatidine was not detected in green fruits but a Δ¹⁶-5α-pregnenolone-like compound was.     

Restriction fragment polymorphisms as probes for plant diversity and their development as tools for applied plant breeding

Summary Maize and tomato cDNA clones have been hybridized in Southern blotting experiments to plant genomic DNA prepared from different lines to detect restriction fragment polymorphisms (RFPs). In maize we have found that a high degree of genetic variability is present, even among domestic inbred lines. Most randomly chosen maize cDNA clones can be used to detect elements of this variability. Similar levels of polymorphism are observed when genomic DNA is digested with any of a number of different restriction enzymes and probed with individual clones. When a clone is hybridized to genomic DNAs prepared from several different maize lines, a number of different alleles are often detected at a single locus. At the same time one clone can often detect more than one independently segregating locus by cross hybridization to related sequences at other loci. As expected these markers are inherited as simple codominant Mendelian alleles from one generation to the next and colinkage of these markers can be demonstrated in the progeny from a heterozygous parent. In similar studies with tomato, remarkably different results were found. Few RFPs were demonstrable among domestic Lycopersicon esculentum lines although a higher level of variability could be detected when comparing esculentum with its wild Lycopersicon relatives. These results are discussed in relation to the applied uses of RFPs in plant breeding as well as the inherent variability of different plant genomes.This work was supported in part by funds from Sandoz Ltd. (Basel, Switzerland) and its subsidiary company, Northrup King Co. (Minneapolis, Minn., U.S.A.) as well as by NSF SBIR grant #BSR-8360870.