Zeatin

About: Zeatin is a research topic. Over the lifetime, 2467 publications have been published within this topic receiving 64092 citations. The topic is also known as: Zeatin & (E/Z)-zeatin.

Morphogenesis and plant regeneration from tissue cultures of Jatropha curcas

Abstract: Techniques for the regeneration of Jatropha curcas L. from various explants have been developed. Regeneration from hypocotyl, petiole and leaf explants was evaluated on a range of concentrations of zeatin, kinetin and N6 benzyladenine (BA) either singly or in combination with indole-3-butyric acid (IBA). Higher regeneration from hypocotyl and petiole explants was obtained on BA with IBA than on zeatin- or kinetin-supplemented media. Leaf discs from the third expanding leaf exhibited higher regeneration potential than those from the fourth leaf. Independent of the explant type, direct adventitious shoot bud induction was recorded highest on MS medium with 2.22 μM BA and 4.9 μM IBA. Although the same BA concentration but with reduced IBA concentration (0.49 μM) proved effective in callus mediated regeneration from hypocotyl and leaf explants, the petioles required lower concentrations of the two growth regulators (0.44 μM BA and 0.49 μM IBA). Regenerated shoots could be rooted on growth regulator-free gelled full-strength MS medium. Following simple hardening procedures, the in vitro-raised plants could be transferred to soil and grown to maturity in the field.

Role of Auxin in Maize Endosperm Development (Timing of Nuclear DNA Endoreduplication, Zein Expression, and Cytokinin).

Abstract: The timing of developmental events and regulatory roles of auxin were examined in maize (Zea mays L.) endosperms. Zeatin, zeatin riboside, and indole-3-acetic acid (IAA) levels were determined by enzyme-linked immunosorbent (ELISA). Zeatin and zeatin riboside increased to maximal concentrations at an early stage (9 d after pollination [DAP]), corresponding to the stage when cell division rate was maximal. In contrast, IAA concentration was low at 9 DAP and abruptly increased from 9 to 11 DAP, thus creating a sharp decline in the cytokinin to auxin ratio. Coincident with the increase in IAA was an increase in DNA content per nucleus, attributed to postmitotic DNA replication via endoreduplication. Exogenous application of 2,4-dichlorophenoxyacetic acid (2,4-D) at 5 or 7 DAP hastened the time course of DNA accumulation per nucleus and increased the average nuclear diameter, whereas 2-(para-chlorophenoxy)isobutyric acid delayed such development. Exogenously applied 2,4-D hastened the accumulation of the zein polypeptides of apparent molecular masses of 12, 14, and 16 kD and the expression of mRNA hybridizing with a zein DNA probe. We conclude that an abrupt increase in auxin induces cellular differentiation events in endosperm, including endoredupliction and expression of particular zein storage proteins.

Cytokinin gene fused with a strong promoter enhances shoot organogenesis and zeatin levels in transformed plant cells

Abstract: The isopentenyltransferase (ipt) gene associated with cytokinin biosynthesis in plants was cloned from a tumor-inducing plasmid carried by Agrobacterium tumefaciens and placed under the control of promoters of differing activities, the cauliflower mosaic virus 35S promoter and the nopaline synthase promoter. These promoter-gene constructs were introduced into wounded Nicotiana stems, leaf pieces, and cucumber seedlings by A. tumefaciens infection. Shoots were observed in the infection site on all responding genotypes of Nicotiana plants infected with the 35S promoter construct (35S—ipt), whereas only 41% responded similarly to infection with the unmodified gene. Furthermore, shoots were observed 19 days after infection with the 35S—ipt gene but not until 28 to 45 days with the unaltered ipt gene. Shoots were more numerous (>40) on galls incited by 35S—ipt and were up to 6 times taller than shoots induced by the native gene. On Cucumis (cucumber), shoots were observed only on galls incited by the 35S—ipt construct. These galls were on the average 7.5 times larger than those incited by the nopaline synthase promoter construct (NOS—ipt) or the unmodified ipt gene. Zeatin and zeatinriboside concentrations averaged 23 times greater in the 35S—ipt transformed shoots than in ones transformed with the native ipt gene. These results suggest that a more active promoter on the ipt gene can enhance or change the morphogenic potential of transformed plant cells by increasing their endogenous cytokinin levels.

Genotypic effects on tissue culture response of lettuce cotyledons

Abstract: A wide range of lettuce (Lactuca sativa L.) cultivars representing the four major morphological types have been screened for tissue culture aptitude, in order to identify genotypes especially amenable for genetic manipulation at the cellular and molecular level. The growth response of lettuce cotyledons showed marked genotypic differences on both callus initiation medium and subsequent transfer to a plant regeneration medium. A new regeneration medium consisting of SH salts and vitamins, 30 g/l sucrose, 7 g/l agar, 0.1 mg/l IAA, 0.5 mg/l kinetin and 0.05 mg/l zeatin, at pH 5.8 substantially improved callus induction and shoot regeneration on cotyledons in most cultivars. Lettuce genotypes exhibiting good regeneration include Greenfields and Summer Gem (Crisphead types), Bronze Mignonette and Green Mignonette (Butterhead types), Salad Bowl (Leaf Type) and Cos and Green Cos (Romaine types)

Micropropagation and field evaluation of micropropagated plants of turmeric

Abstract: A protocol was developed for in vitro propagation of turmeric cv `elite' using young vegetative buds from sprouting rhizomes. The shoot buds produced multiple shoots when cultured on MS solid medium supplemented with benzyladenine and 1-naphthalene acetic acid. The effect of various cytokinins on shoot multiplication was studied by culturing the shoot tips on MS liquid medium supplemented with benzyladenine, benzyladenine riboside, kinetin, kinetin riboside, zeatin, 6-γ,γ-dimethylallylaminopurine, adenine, adenine sulfate or metatopolin each at 10 μM in combination with 1-naphthalene acetic acid (1 μM). Significant differences were observed between the treatments. Liquid medium was more favourable than agar medium for shoot multiplication. Among the various concentrations of agar tested, 0.4% and 0.6% were the best and produced the highest number of shoots per explant. Among the different carbohydrates tested, sucrose, fructose, glucose, sugar cubes, maltose, levulose and market sugar were found to be equally effective for shoot multiplication and xylose, rhamnose, lactose and soluble starch were inhibitory. Ninety five percent of the micropropagated plants survived in sterilized soil in paper cups and all of them survived in the field. Among 48 plants, two plants showed variegated leaves on the tillers. The micropropagated plants showed a significant increase in shoot length, number of tillers, number and length of leaves, number of fingers and total fresh rhizome weight per plant when compared with conventionally propagated plants. RAPD analysis of 11 regenerated plants using sixteen 10-mer primers did not show any polymorphism.