Rockefeller University

About: Rockefeller University is a education organization based out in New York, New York, United States. It is known for research contribution in the topics: Population & Gene. The organization has 15867 authors who have published 32938 publications receiving 2940261 citations. The organization is also known as: Rockefeller University & Rockefeller Institute.

The WUSCHEL gene promotes vegetative-to-embryonic transition in Arabidopsis.

Abstract: Formation of somatic embryos in plants is known to require high concentrations of auxin or 2,4-dichlorophenoxyacetic acid (2,4-D), which presumably acts to trigger a signalling cascade. However, very little is known about the molecular mechanism that mediates the vegetative-to-embryogenic transition. We have employed a genetic approach to dissect the signal transduction pathway during somatic embryogenesis. In a functional screen using a chemical-inducible activation-tagging system, we identified two alleles of Arabidopsis gene PGA6 whose induced overexpression caused high-frequency somatic embryo formation in all tissues and organs tested, without any external plant hormones. Upon inducer withdrawal, all these somatic embryos were able to germinate directly, without any further treatment, and to develop into fertile adult plants. PGA6 was found to be identical to WUSCHEL (WUS), a homeodomain protein previously shown to be involved in specifying stem cell fate in shoot and floral meristems. Transgenic plants carrying an estradiol-inducible XVE-WUS transgene can phenocopy pga6-1 and pga6-2. Our results suggest that WUS/PGA6 also plays a key role during embryogenesis, presumably by promoting the vegetative-to-embryogenic transition and/or maintaining the identity of the embryonic stem cells.

Structural Basis of Transcription Initiation: RNA Polymerase Holoenzyme at 4 Å Resolution

Abstract: The crystal structure of the initiating form of Thermus aquaticus RNA polymerase, containing core RNA polymerase (alpha2betabeta'omega) and the promoter specificity sigma subunit, has been determined at 4 angstrom resolution. Important structural features of the RNA polymerase and their roles in positioning sigma within the initiation complex are delineated, as well as the role played by sigma in modulating the opening of the RNA polymerase active-site channel. The two carboxyl-terminal domains of sigma are separated by 45 angstroms on the surface of the RNA polymerase, but are linked by an extended loop. The loop winds near the RNA polymerase active site, where it may play a role in initiating nucleotide substrate binding, and out through the RNA exit channel. The advancing RNA transcript must displace the loop, leading to abortive initiation and ultimately to sigma release.

Mechanisms of neural patterning and specification in the developing cerebellum

Abstract: The cerebellar cortex is one of the best-studied regions of the CNS. For nearly a century, all of the cerebellar cell types and the patterns of their synaptic connections have been known. Much of this wealth of information comes from Ramon y Cajal's work (1889, 1911, 1960) with Golgi studies. Further infor­ mation on the development (Altman & Bayer 1985a-c, Rakic 1971, Miale & Sidman 1961), anatomy (Palay & Chan-Palay 1974), fiber tracts (BrodaI1981), and circuitry (Llinas & Hillman 1969) of the cerebellar cortex has emerged over the past several decades. The cerebellum provides a unique system for studying CNS development, combining the three classic patterns of CNS development-morphogenetic movements, the formation of ganglionic struc­ tures, and the establishment of neuronal layers-within one brain region. Remarkably simple in its basic plan, the adult cerebellar cortex contains only three layers and two principal classes of neurons. The abundance of one of these principal neurons, the granule cell, has enabled detailed analyses of the molecular mechanisms that underlie the basic steps in neuronal differentiation and has pointed out the role of local community factors in CNS neuronal development. Moreover, studies of naturally occurring mutations (Heintz et al 1993, Sidman 1968) and of targeted gene disruptions that block discrete steps in the development of this region (McMahon 1993, Joyner & Hanks 1991,