, Framingham, MA), whereas cytokinins (CKs) were determined using the methodology of Nicander et al. (1993) . Floral malformation assessment. At full bloom, trees were inspected for malformed floral panicles, which characterized by compacted, stunted
Hanan M. El-Hoseiny, Mohamed N. Helaly, Nabil I. Elsheery, and Shamel M. Alam-Eldein
Ying Chen, Xinlu Chen, Fei Hu, Hua Yang, Li Yue, Robert N. Trigiano, and Zong-Ming (Max) Cheng
). Micropropagated shoots can be readily rooted either in vitro or ex vitro, and acclimatized to greenhouse conditions. The most important factors in successfully micropropagating A. american were cytokinin and auxin levels. Cytokinin in the medium was reported to
Sadiye Hayta, Mark A. Smedley, Jinhong Li, Wendy A. Harwood, and Philip M. Gilmartin
plant material and failed to initiate callus ( Table 1 ). Chemically, TDZ is completely different from other commonly used auxins and cytokinins, but has been shown to exhibit both auxin and cytokinin like affects due to its ability to modulate
Ann C. Smigocki and Freddi A. Hammerschlag
Immature `Redhaven' peach [Prunus persica (L.) Batsch] embryos were infected with a shooty mutant strain of Agrobacterium tumefaciens, tms328::Tn5, which carries an octopine-type Ti plasmid with a functional cytokinin gene and a mutated auxin gene. Shoots were regenerated from embryo-derived callus that was initiated on MS medium lacking phytohormones. Shoots exhibited increased frequency of branching and were more difficult to root than the noninfected. Transcripts of the tms328::Tn5-cytokinin gene were detected using northern analyses of total plant RNA. Polymerase chain reaction of genomic DNA and cDNA resulted in amplification of DNA fragments specific for the cytokinin gene, as determined by restriction enzyme and Southern analyses. The concentrations of the cytokinins zeatin and zeatin riboside in the leaves of regenerated plants were on the average 51-fold higher than in leaves taken from nontransformed plants. None of the shoots or callus tissues were postive for octopine. The expression of the T-DNA encoded cytokinin gene promotes growth of peach cells in the absence of phytohormones, thus serving as a marker for transformation. In addition, this gene appears to promote morphogenesis without an auxin inductive step.
Sandra L. Barbour, D.A. Schaff, A.C. Smigocki, and J.J. Frett
The ipt gene of Agrobacterium tumefaciens T-DNA encodes for isopentenyl transferase, which is an enzyme active in cytokinin biosynthesis. While it is known that cytokinins are associated with in vitro promotion of cell division and stimulation of shoot production, little is known about their mode of action. As the first step in localizing cytokinin synthesis, we present a cloning and expression strategy for the ipt gene. The source of the ipt gene was Agrobacterium tumefaciens octopine Ti plasmid 15955. The ipt gene was amplified by the polymerase chain reaction (PCR) and cloned into pMal-c2 (New England Biolabs, Beverly, MA). This construct was transformed into E. coli and the ipt gene was expressed as a fusion protein. The protein was purified by affinity chromatography to serve as an antigen for polyclonal antibody production. These antibodies will be used to localize isopentenyl transferase in plant tissue.
Laise S. Moreira and Matthew D. Clark
medium supplemented with PGR [cytokinin (BA), indole-3-butyric acid, gibberellic acid, and casein hydrolysate (CH)] in the culture medium showed the greatest number of normal plantlets (46.98%; P > 0.05). In agreement with Li et al. (2020b ), these
Graham H. Barry and Smit le Roux
roots, beside other organs, are a major site for the biosynthesis of gibberellins and cytokinins, which are antagonistic to rind color development and are subsequently transported to the aerial portion of the tree through the xylem ( Saidha et al., 1983
Yanjiao Zheng, Zaiqiang Yang, Chao Xu, Lin Wang, Haijing Huang, and Shiqiong Yang
, T.C. Kopsell, D.A. Sams, C.E. 2016 Abscisic acid improves tomato fruit quality by increasing soluble sugar concentrations J. Plant Nutr. 40 964 973 Binns, A.N. 1994 Cytokinin accumulation and action: Biochemical, genetic, and molecular approaches
Sandra L. Barbour, Margaret J. McMahon, John J. Frett, and Dennis R. Decoteau
Similarities exist between the effects of phytochrome and cytokinins on plant growth and development (e.g., chloroplast development, amaranthin synthesis. seed germination, photomorphogenesis). It is unclear, however, if and how these two systems interact.
As a beginning step to determine cytokinin-phytochrome interactions, we developed a strategy utilizing ipt -transgenic tobacco in phytochrome/light treatment investigations. The sour-cc of the ipt gene was Agrobacterium tumefaciens Ti plasmid 15955. This gene encodes for isopentenyl transferase which is an enzyme active in cytokinin biosynthesis.
Ipt -transgenic tobacco cultures (grown on MS medium supplemented with kanamycin but no plant growth regulators) were treated with end-of-day red or far-red light for 15 minutes. After 30 days of treatment, the plant tissue was harvested and either homogenized for SDS-PAGE or fixed for transmission electron microscopic analysis.
Results from immuno-gold labelling using polyclonal antibodies specific to iptase will he used to Indicate the influence of phytochrome on cytokinin activity. Also, structural changes at the ultra-cellular level will be determined.
Robert Price, Marihelen Kamp-Glass, and David Powell
Venus fly trap, Dionaea muscipula Ellis, leaf sections were surfaced sterilized under aseptic conditions. The leaf sections were cultured in reduced strength Muashige and Skoog growth medium supplemented with 2,25 mg/l 6-Benzylaminopurine and 1.0-2.0 mg/l Kinetin. The various levels of cytokinin were used to differentiate and enhance callus formation.