Biological systems of the host cell involved in Agrobacterium infection

Genetic transformation of plants by Agrobacterium , which in nature causes neoplastic growths, represents the only known case of trans -kingdom DNA transfer. Furthermore, under laboratory conditions, Agrobacterium can also transform a wide range of other eukaryotic species, from fungi to sea urchins to human cells. How can the Agrobacterium virulence machinery function in such a variety of evolutionarily distant and diverse species? The answer to this question lies in the ability of Agrobacterium to hijack fundamental cellular processes which are shared by most eukaryotic organisms. Our knowledge of these host cellular functions is critical for understanding the molecular mechanisms that underlie genetic transformation of eukaryotic cells. This review outlines the bacterial virulence machinery and provides a detailed discussion of seven major biological systems of the host cell–cell surface receptor arrays, cellular motors, nuclear import, chromatin targeting, targeted proteolysis, DNA repair, and plant immunity – thought to participate in the Agrobacterium -mediated genetic transformation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75425/1/j.1462-5822.2006.00830.x.pd

Interlinking showy traits: co-engineering of scent and colour biosynthesis in flowers

The phenylpropanoid pathway gives rise to metabolites that determine floral colour and fragrance. These metabolites are one of the main means used by plants to attract pollinators, thereby ensuring plant survival. A lack of knowledge about factors regulating scent production has prevented the successful enhancement of volatile phenylpropanoid production in flowers. In this study, the Production of Anthocyanin Pigment1 ( Pap1 ) Myb transcription factor from Arabidopsis thaliana , known to regulate the production of non-volatile phenylpropanoids, including anthocyanins, was stably introduced into Petunia hybrida . In addition to an increase in pigmentation, Pap1 -transgenic petunia flowers demonstrated an increase of up to tenfold in the production of volatile phenylpropanoid/benzenoid compounds. The dramatic increase in volatile production corresponded to the native nocturnal rhythms of volatile production in petunia. The application of phenylalanine to Pap1 -transgenic flowers led to an increase in the otherwise negligible levels of volatiles emitted during the day to nocturnal levels. On the basis of gene expression profiling and the levels of pathway intermediates, it is proposed that both increased metabolic flux and transcriptional activation of scent and colour genes underlie the enhancement of petunia flower colour and scent production by Pap1 . The co-ordinated regulation of metabolic steps within or between pathways involved in vital plant functions, as shown here for two showy traits determining plant–pollinator interactions, provides a clear advantage for plant survival. The use of a regulatory factor that activates scent production creates a new biotechnological strategy for the metabolic architecture of fragrance, leading to the creation of novel genetic variability for breeding purposes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75040/1/j.1467-7652.2008.00329.x.pd

Towards targeted mutagenesis and gene replacement in plants.

International audienceAdvances in the development of biotechnological tools for plant gene disruption and repair have lagged behind the rapid progress made in whole-genome sequencing of many model and crop plant species. Plant DNA-repair machinery predominantly uses non-homologous end-joining (NHEJ), making the homologous recombination (HR)-based methods, which have proved fruitful for gene targeting in non-plant systems, unsuitable for use in plant systems. Two recent reports describe successful targeted mutagenesis and gene targeting in Arabidopsis by either harnessing the plant NHEJ machinery using site-specific induction of double-strand breaks (DSBs), or by activation of a HR pathway through overexpression of a yeast DNA recombination gene in transgenic plants. These reports provide a foundation from which new technologies for site-specific genome alterations in plant species can be developed

VIP1, an Arabidopsis protein that interacts with Agrobacterium VirE2, is involved in VirE2 nuclear import and Agrobacterium infectivity

T-DNA nuclear import is a central event in genetic transformation of plant cells by Agrobacterium. This event is thought to be mediated by two bacterial proteins, VirD2 and VirE2, which are associated with the transported T-DNA molecule. While VirD2 is imported into the nuclei of plant, animal and yeast cells, nuclear uptake of VirE2 occurs most efficiently in plant cells. To understand better the mechanism of VirE2 action, a cellular interactor of VirE2 was identified and its encoding gene cloned from Arabidopsis. The identified plant protein, designated VIP1, specifically bound VirE2 and allowed its nuclear import in non-plant systems. In plants, VIP1 was required for VirE2 nuclear import and Agrobacterium tumorigenicity, participating in early stages of T-DNA expression