T‐DNA tagging reveals a novel cDNA triggering cytokinin‐ and auxin‐independent protoplast division

Abstract

basis of action in plants is fragmentary. Plants may synthes-Cordeiro 1 , Els Prinsen 2 , Jeff Schell 1 and Richard ize cytokinins either directly by addition of isopentenylpyro-Walden 1,* phosphate to AMP by an adenylate:isopentenyltransferase 1 Max-Planck-Institut fü r Zü chtungsforschung, Carl-von-(cytokinin synthase) producing isopentenyladenosine 5Ј Linne-Weg 10, 50829 Kö ln, Germany, and phosphate ([9R-5ЈP]iP) which in turn serves as an inter-

Re‐evaluation of phytohormone‐independent division of tobacco protoplast‐derived cells

“…These findings are in contrast to data presented in previous publications ( Ichikawa et al . 1997 ; Miklashevichs et al . 1997 ; van de Sande et al .…”

“…Using activation T‐DNA tagging, cytokinin‐independent mutants of Arabidopsis have indeed been generated which allow the identification of a gene involved in cytokinin signal transduction ( Kakimoto 1996), thus confirming the general validity of the activation gene tagging approach. However, it was reported that cultured cells isolated from the tagged mutant plants cyi1 ( Miklashevichs et al . 1997 ), axi4/1 ( Harling et al .…”

“…1994 ), were able to divide in the absence of externally supplied auxin. In addition, protoplast‐derived cells from cyi1 plants were claimed to divide without exogenously added cytokinin and auxin ( Miklashevichs et al . 1997 ).…”

“…1994 ), axi4/1 ( Harling et al . 1997 ) and cyi1 ( Miklashevichs et al . 1997 ), which were generated by activation T‐DNA tagging, were unable to grow in the absence of auxin or cytokinin.…”

The Impact of Ti-Plasmid-Derived Gene Vectors on the Study of the Mechanism of Action of Phytohormones

“…The dominant mutation obtained allows selection for a predetermined phenotype. To date, this approach has been used to create tobacco protoplast lines able to grow in the absence of auxin (39); cytokinin (77), or in the presence of an inhibitor of polyamine biosynthesis (28); as well as a mutant callus of Catherostigma plantagineum changed in response to dessication (29); and Arabidopsis callus able to form shoots in the absence of cytokinins (50). The genes tagged include axi1, which affects gene expression (115); cyi1, a small peptide growth factor (77) and cki1, a two-component receptor kinase (50); and factors involved in the regulation of seed maturation (88).…”