Correlation between Lack of Receptacle Growth in Response to Auxin and Accumulation of a Specific Polypeptide in a Strawberry (Fragaria ananassa Duch.) Variant Genotype

Receptacle growth in strawberry (Fragaria ananassa Duch. cv.Ozark Beauty) occurred after either pollination or auxin treatment.In a strawberry variant genotype (Washington State UniversitySelection No. 12/13), pollination did not lead to receptaclegrowth but application of -naphthaleneacetic acid (NAA) at anthesisresulted in normal receptacle growth. The receptacles of OzarkBeauty retained their ability to respond to auxin at least upto 36 days after anthesis. However, delay of auxin applicationto the receptacles of the variant genotype resulted in decreasedauxin-responsive growth and auxin application after the 10thday of anthesis led to very little growth. The loss of auxin-responsivegrowth of the receptacle of the variant genotype was not associatedwith any loss of auxin binding activity of receptacle membranes.If auxin was not supplied to the receptacles of the variantgenotype at anthesis, the receptacles did not grow and a polypeptideof 52,000 M_r accumulated. Application of NAA to the receptaclesof the variant genotype at anthesis or on the fifth day afteranthesis resulted in the growth of the receptacle and the 52,000M_r polypeptide did not accumulate. Application of NAA to thereceptacles of the variant genotype on the 10th or the 15thday after anthesis led to very little growth of the receptacleand the 52,000 M_r polypeptide accumulated to high levels. Theseresults suggested a correlation between the lack of receptaclegrowth in response to auxin and accumulation of the 52,000 M_rpolypeptide. ¹ Current adress: The Institute of Applied Research, Ben GurionUniversity of the Negev, Beer-Sheva, Israel. (Received August 6, 1984; Accepted December 11, 1984)     

Rice scutellum induces Agrobacterium tumefaciens vir genes and T-strand generation

For successful transformation of a plant by Agrobacterium tumefaciens it is essential that the explant used in cocultivation has the ability to induce Agrobacterium tumour-inducing (Ti) plasmid virulence (vir) genes. Here we report a significant variation in different tissues of Indica rice (Oryza sativa L. cv. Co43) in their ability to induce Agrobacterium tumefaciens vir genes and T-strand generation, using explants preincubated in liquid Murashige and Skoog (MS) medium. An analysis of rice leaf segments revealed that they neither induced vir genes nor inhibited vir gene induction. Of different parts of rice plants of different ages analysed only scutellum from four-day old rice seedlings induced vir genes and generation of T-strands. We observed that the physical presence of preincubated scutella is required for vir gene induction. Conditioned medium from which preincubated scutella were removed did not induce the vir genes. Scutellum-derived calli, cultured for 25 days on medium containing 2,4-D, also induced virE to an appreciable level. These results suggest that scutellum and scutellum-derived calli may be the most susceptible tissues of rice for Agrobacterium-mediated transformation.     

Auxin-regulated polypeptide changes at different stages of strawberry fruit development

The pattern of polypeptides at different stages of strawberry (Fragaria ananassa Duch. cv Ozark Beauty) fruit development was studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. An 81,000-dalton polypeptide appeared between 5 and 10 days after pollination. Polypeptides with molecular weights of 76,000 and 37,000 daltons were formed after 10 days. The control exerted by auxin in the stage-specific formation of polypeptides was investigated by stopping fruit growth after removing the achenes and reinitiating fruit growth by the application of a synthetic auxin, α-naphthaleneacetic acid (NAA). When the achenes were removed from the 5- and 10-day-old fruits, the fruits failed to grow, the 81,000 dalton polypeptide was not formed between 5 and 10 days, and the 76,000- and 37,000-dalton polypeptides were not formed between 10 and 20 days. Application of NAA to fruits deprived of auxin by removal of achenes resulted in the resumption of growth and also in the appearance of these polypeptides. Removal of achenes of the 5- or 10-day-old fruits and growing them without auxin resulted in the formation of 52,000- and 57,000-dalton polypeptides. These two polypeptides were not formed when NAA was applied to fruits after removal of achenes. Supply of NAA to auxin-deprived fruits 5 days after removal of achenes resulted in resumption of growth and also in the disappearance of these two polypeptides, pointing out their possible relation to the inhibition of fruit growth.     

Trehalose Toxicity in Cuscuta reflexa: Cell Wall Synthesis Is Inhibited upon Trehalose Feeding

α,α-Trehalose induced a rapid blackening of the terminal 2.5-centimeter region of excised Cuscuta reflexa Roxb. vine. The incorporation of radioactivity from [¹⁴C]glucose into alkali-insoluble fraction of shoot tip was markedly inhibited by 12 hours of trehalose feeding to an excised vine. This inhibition was confined to the apical segment of the vine in which cell elongation occurred. The rate of blackening of shoot tip explants was hastened by the addition of gibberellic acid A₃, which promoted elongation growth of isolated Cuscuta shoot tips. The symptom of trehalose toxicity was duplicated by 2-deoxyglucose, which has been shown to be a potent inhibitor of cell wall synthesis in yeast. The observations suggest that trehalose interferes with the synthesis of cell wall polysaccharides, the chief component of which was presumed to be cellulose.     

Phenothiazine–rhodamine‐based colorimetric and fluorogenic ‘turn‐on' sensor for Zn2+ and bioimaging studies in live cells

A phenothiazine–rhodamine (PTRH) fluorescent dyad was synthesized and its ability to selectively sense Zn²⁺ ions in solution and in in vitro cell lines was tested using various techniques. When compared with other competing metal ions, the PTRH probe showed the high selectivity for Zn²⁺ ions that was supported by electronic and emission spectral analyses. The emission band at 528 nm for the PTRH probe indicated the ring closed form of PTRH, as for Zn²⁺ ion binding to PTRH, the λ_em get shift to 608 nm was accompanied by a pale yellow to pink colour (under visible light) and green to pinkish red fluorescence emission (under UV light) due to ring opening of the spirolactam moiety in the PTRH ligand. Spectral overlap of the donor emission band and the absorption band of the ring opened form of the acceptor moiety contributed towards the fluorescence resonance energy transfer ON mechanism for Zn²⁺ ion detection. The PTRH sensor had the lowest detection limit for Zn²⁺, found to be 2.89 × 10^?8 M. The sensor also demonstrated good sensing application with minimum toxicity for in vitro analyses using HeLa cells.     

A New DNA‐Intercalative Cytotoxic Allylic Xanthone from Swertia corymbosa

Phytochemical investigation of the CHCl₃ fraction of Swertia corymbosa resulted in the isolation of a new 3‐allyl‐2,8‐dihydroxy‐1,6‐dimethoxy‐9H‐xanthen‐9‐one ( 1 ), along with four known xanthones, gentiacaulein ( 3 ), norswertianin ( 4 ), 1,3,6,8‐tetrahydroxyxanthone ( 5 ), and 1,3‐dihydroxyxanthone ( 6 ). Structure of compound 1 was elucidated with the aid of IR, UV, NMR, and MS data, and chemical transformation via new allyloxy xanthone derivative ( 2 ). Compounds 1 – 6 exhibited various levels of antioxidant and anti‐α‐glucosidase activities. Absorption and fluorescence spectroscopic studies on 1 – 6 indicated that these compounds could interact with calf thymus DNA (CT‐DNA) through intercalation and with bovine serum albumin (BSA) in a static quenching process. Compound 1 was found to be significantly cytotoxic against human cancer cell lines HeLa, HCT116, and AGS, and weakly active against normal NIH 3T3 cell line.     

Establishment of homozygous transgenic rice lines after elimination of unlinked albino traits from transgenic events through segregation

In an analysis of 339 independent T ₀ transgenic rice lines generated by Agrobacterium-mediated transformation, albino plants appeared in the T ₁ generation in two single-copy transgenic lines, O54 and O36 and in one double-copy transgenic line, C18. While the T ₀ plants of these three lines were green, albino and green plants emerged in a 1:3 ratio in the T ₁ generation. The albino phenotype segregated as a monogenic recessive trait. Southern blot analysis of the green and albino plants in the T ₁ generation confirmed that the albino trait and the T-DNA insertion events were unlinked. Segregation of the albino trait from the transgenic trait in the lines O54 and O36 was confirmed in T ₂ and T ₃ generations, respectively. Homozygous transgenic plants free from the albino trait were also identified. In the double-copy transgenic line C18, we genetically separated the two transgenic loci, out-segregated the albino locus from both transgene loci, and identified homozygous plants for each of the transgenic events by Southern blot analysis in the T ₁ generation itself. Thus, we demonstrate that when an albino trait appears in the T ₁ generation and is unlinked to a transgene locus, the albino locus can be segregated from the transgene locus and homozygous transgenic lines free from albinos can be established.