Toshio Murashige

Bio: Toshio Murashige is an academic researcher from University of California, Riverside. The author has contributed to research in topics: Callus & Tissue culture. The author has an hindex of 23, co-authored 38 publications receiving 1954 citations.

Evaluation of parameters in the isolation of viable protoplasts from cultured tobacco cells.

Abstract: A systematic evaluation disclosed the following conditions to be optimum for the isolation of viable protoplasts from cultured cells of Nicotiana tabacum L. `Bright Yellow9 grown in liquid suspensions: ( a ) the cell culture in the early phase of cell number increase, ( b ) an enzyme mixture of 1% cellulase “Onozuka” and 0.2% Macerozyme, ( c ) an enzyme solution pH of 4.7 or 5.7, ( d ) a 2- to 3-hr incubation period, ( e ) 5 ml of enzyme solution per 500 mg cells and contained in a 50-ml Delong flask, ( f ) agitation on a gyrotory shaker at 50 rpm, and ( g ) 0.3 to 0.8 m mannitol as osmoticum in the cell enzyme mixture. The incubation temperature may be varied from 22 to 37 C. The procedure enabled 30% of the tobacco cells to form protoplasts, 80% of which regenerated cell walls in 4 days and 40% resumed cell division activity when returned to cell culture medium.

Some histochemical changes underlying shoot initiation in tobacco callus cultures

Abstract: A comparative histochemical study of changes in nucleic acids, proteins, and carbohydrates was performed on freeze-substituted samples of tobacco callus, cultured under shoot-forming and non-organ-...

Chromosome complement as a determinant of the morphogenic potential of tobacco cells

Abstract: A B S T R A C T Polysomatism in Nicotiana tabacum L. 'Wisconsin 38' was confirmed. Pith samples from the region of the stem 3.5-10.5 cm below the apex contained nearly equal proportions of diploid and tetraploid cells and samples obtained further down, 15.5-22.5 cm, showed predominantly tetraploid (circa 70%) and smaller proportions of diploid (9%), octaploid (16%), and aneuploid (5%) cells. Cultures of the callus from pith explants showed no evidence of diploid cells after 1 year, but did show roughly half 4n and 8n euploid and half -aneuploid cells. The callus after 6 years in vitro consisted entirely of aneuploid cells. The attainment of this predominance of aneuploid cells could account for the decline of callus growth and organ formation of tobacco tissue cultures. Tobacco tissue cultures started from single cells disclosed that totipotentiality was not restricted to diploid cells but was possessed by and expressed with apparently equal ease by tetraploid cells. The morphogenetically depressed situation was associated with a highly variable aneuploidy. With increase in somatic age the frequency of aneuploid cells increased and the level of ploidy among the aneuploid cells shifted from sub-tetraploidy to above tetraploidy.

Rejuvenation of Sequoia sempervirens by Repeated Grafting of Shoot Tips onto Juvenile Rootstocks in Vitro: Model for Phase Reversal of Trees

Abstract: Repeated grafting of 1.5-centimeter long shoot tips from an adult Sequoia sempervirens tree onto fresh, rooted juvenile stem cuttings in vitro resulted in progressive restoration of juvenile traits. After four successive grafts, stem cuttings of previously adult shoots rooted as well, branched as profusely, and grew with as much or more vigor as those of seedling shoots. Reassays disclosed retention for 3 years of rooting competence at similar levels as originally restored. Adventitious shoot formation was remanifested and callus development was depressed in stem segments from the repeatedly grafted adult. The reversion was associated with appearance and disappearance of distinctive leaf proteins. Neither gibberellic acid nor N(6)-beneyladenine as nutrient supplements duplicated the graft effects.

Somaclonal variation — a novel source of variability from cell cultures for plant improvement

Abstract: It is concluded from a review of the literature that plant cell culture itself generates genetic variability (somaclonal variation). Extensive examples are discussed of such variation in culture subclones and in regenerated plants (somaclones). A number of possible mechanisms for the origin of this phenomenon are considered. It is argued that this variation already is proving to be of significance for plant improvement. In particular the phenomenon may be employed to enhance the exchange required in sexual hybrids for the introgression of desirable alien genes into a crop species. It may also be used to generate variants of a commercial cultivar in high frequency without hybridizing to other genotypes.

The role of the monopteros gene in organising the basal body region of the Arabidopsis embryo

Abstract: The monopteros (mp) gene contributes to apical-basal pattern formation in the Arabidopsis embryo. mp mutant seedlings lack basal body structures such as hypocotyl, radicle and root meristem, and this pattern deletion has been traced back to alterations in the octant-stage embryo. Cells of the embryo proper and the uppermost cell of the suspensor fail to establish division patterns that would normally generate the basal body structures. The resulting absence of a morphological axis seems to be responsible for another phenotypic trait of mp seedlings, variable positioning of cotyledons. This relationship is suggested by weak mp seedling phenotypes in which the presence of a short hypocotyl is correlated with normal arrangement of cotyledons. Root formation has been induced in mp seedlings grown in tissue culture. This result supports the notion that the mp gene is required for organising the basal body region, rather than for making the root, in the developing embryo.

Agriculture, Forestry and Fisheries

Abstract: Agriculture and fishing are the primary source of almost all our food, as well as of many other products, so remain vital activities even though their share in the economy is small and in continuous decline. Partly for this reason public policy in these areas is almost entirely integrated at European level in the Common Agricultural Policy (CAP) and Common Fisheries Policy (CFP). Forestry policies are also heavily affected by EU-level decision-making. As agriculture dominates in terms of direct contribution to GDP and numbers of people engaged in it, as well as accounting for the largest amount of public support expenditure, it is agriculture that will receive the greatest attention here.

Plant hormones and plant growth regulators in plant tissue culture

Abstract: This is a short review of the classical and new, natural and synthetic plant hormones and growth regulators (phytohormones) and highlights some of their uses in plant tissue culture. Plant hormones rarely act alone, and for most processes— at least those that are observed at the organ level—many of these regulators have interacted in order to produce the final effect. The following substances are discussed: (a) Classical plant hormones (auxins, cytokinins, gibberellins, abscisic acid, ethylene and growth regulatory substances with similar biological effects. New, naturally occurring substances in these categories are still being discovered. At the same time, novel structurally related compounds are constantly being synthesized. There are also many new but chemically unrelated compounds with similar hormone-like activity being produced. A better knowledge of the uptake, transport, metabolism, and mode of action of phytohormones and the appearance of chemicals that inhibit synthesis, transport, and action of the native plant hormones has increased our knowledge of the role of these hormones in growth and development. (b) More recently discovered natural growth substances that have phytohormonal-like regulatory roles (polyamines, oligosaccharins, salicylates, jasmonates, sterols, brassinosteroids, dehydrodiconiferyl alcohol glucosides, turgorins, systemin, unrelated natural stimulators and inhibitors), as well as myoinositol. Many of these growth active substances have not yet been examined in relation to growth and organized developmentin vitro.