Plants develop unorganized cell masses like callus and tumors in response to various biotic and abiotic stimuli. Since the historical discovery that the combination of two growth-promoting hormones, auxin and cytokinin, induces callus from plant explants in vitro, this experimental system has been used extensively in both basic research and horticultural applications. The molecular basis of cal...

Center for Plant Molecular Biology, Department of General Genetics (M.S., F.H.), and Proteome Center Tuebingen, Interfaculty Institute for Cell Biology (T.L., J.M., A.N.), University of Tuebingen, 72076 Tuebingen, Germany; Institute for Crop Production and Grassland Research, Bioinformatics Unit, University of Hohenheim, 70599 Stuttgart, Germany (A.S., H.-P.P.); and DuPont Crop Genetics Researc...

Flowering process governs seed set and thus affects agricultural productivity. Soybean, a major legume crop, requires short-day photoperiod conditions for flowering. While leaf-derived signal(s) are essential for the photoperiod-induced floral initiation process at the shoot apical meristem, molecular events associated with early floral transition stages in either leaves or shoot apical meriste...

As multicellular organisms grow, positional information is continually needed to regulate the pattern in which cells are arranged. In the Arabidopsis root, most cell types are organized in a radially symmetric pattern; however, a symmetry-breaking event generates bisymmetric auxin and cytokinin signaling domains in the stele. Bidirectional cross-talk between the stele and the surrounding tissue...

Suspension cultures were incubated in the presence and absence of gibberellic acid (GA(3)) in an attempt to define a new experimental system for study of the molecular action of gibberellins upon growth. Unlike many suspension cultures, an auxin-independent green clone from spinach (Spinacia oleracea L.) and an auxin-dependent line of "Paul's Scarlet" rose (Rosa sp.) were promoted in expansion ...

Asymmetric distribution of the hormone auxin organizes plant cell fate and drives specification of new organs. Such asymmetries are regulated by polarized auxin transporters called PINs. But what controls PIN polarity? A new study shows that another hormone, cytokinin, degrades PINs on specific membranes to direct auxin flux.

Pith tissue from Nicotiana tabacum L. cv ;Maryland Mammoth' or ;Wisconsin 38' was isolated, free of vascular tissue, and cultured on a medium containing auxin but no cytokinin. Explants from the apical 1 cm of stem, within the pith rib meristem, initiated callus growth with 100% efficiency. Macroscopically visible callus was evident 5 days after the tissue was isolated, and the cultures grew pe...

Circadian systems coordinate endogenous events with external signals. In mammals, hormone-clock feedbacks are a well-known integration system. Here, we investigated phytohormone effects on plant-circadian rhythms via the promoter:luciferase system. We report that many hormones control specific features of the plant-circadian system, and do so in distinct ways. In particular, cytokinins delay ci...

Protocorm pieces of the orchid Cymbidium were aseptically cultured either without phytohormones, or with one of the growth promoting substances, auxin cytokinin, and gibberellin. The derivative melting profiles of the extracted DNA's differ from each other with respect to the size of various AT- and GC- rich fractions. Evidence has been obtained for the increase of the more AT--rich fractions i...

The Medicago truncatula LATD/NIP gene is essential for the development of lateral and primary root and nitrogen-fixing nodule meristems as well as for rhizobial invasion of nodules. LATD/NIP encodes a member of the NRT1(PTR1) nitrate and di-and tri-peptide transporter family, suggesting that its function is to transport one of these or another compound(s). Because latd/nip mutants can have thei...