Phytochrome regulation of nuclear gene expression in plants

The photoregulation of gene expression in higher plants was extensively studied during the 1980s, in particular the light-responsive cis -acting elements and trans -acting factors of the Lhcb and rbcS genes. However, little has been discovered about: (1) which plant genes are regulated by light, and (2) which photoreceptors control the expression of these genes. In the 1990s, the functional analysis of the various photoreceptors has progressed rapidly using photoreceptor-deficient mutants, including those of the phytochrome gene family. More recently however, advanced techniques for gene expression analysis, such as fluorescent differential display and DNA microarray technology, have become available enabling the global identification of genes that are regulated by particular photoreceptors. In this paper we describe distinct and overlapping effects of individual phytochromes on gene expression in Arabidopsis thaliana.     

Phytochrome gene diversity

The structures and functions of the phytochrome apoprotein genes (the PHY genes), their diversity across the plant kingdom, and their evolution are central concerns in the study of red-light sensing in plants. We summarize here recent advances in two areas relating to these topics: (1) the characteristics of the PHY gene family in Arabidopsis thaliana, the higher plant species for which the most extensive information on these genes is available, and (2) the similarity relationships, phylogeny, and evolutionary implications of PHY gene sequences and partial sequences which have been described from various plants. Together, these two areas of study, one directed at understanding in detail the phytochromes present in a single species and the other directed at a much broader understanding of PHY gene relatedness and distribution, are producing an increasingly clear picture of the diversity and evolution of plant red-light photoreceptors. Moreover, they suggest that the complexity of the phytochrome family has increased as land plants have evolved novel morphologies.     

Chemically regulated gene expression in plants

Chemically inducible systems that activate or inactivate gene expression have many potential applications in the determination of gene function and in plant biotechnology. The precise timing and control of gene expression are important aspects of chemically inducible systems. Several systems have been developed and used to analyze gene function, marker-free plant transformation, site-specific DNA excision, activation tagging, conditional genetic complementation, and restoration of male fertility. Chemicals that are used to regulate transgene expression include the antibiotic tetracycline, the steroids dexamethasone and estradiol, copper, ethanol, the inducer of pathogen-related proteins benzothiadiazol, herbicide safeners, and the insecticide methoxyfenozide. Systems that are suitable for field application are particularly useful for experimental systems and have potential applications in biotechnology.     

Adeno-cosmid cloning vectors for regulated gene expression

Background

Adenovectors are widely used for efficient delivery of genes into a variety of cell types and organisms. However, the construction of the desired vector/genes combination, especially if it involves the cloning of several gene cassettes, can be laborious due to the large size of these vectors. New methods are needed to simplify the construction of complex combinations of gene cassettes into adenovectors.

Methods

Using simple cloning techniques and exploiting the λ‐phage packaging system, we devised efficient methods for the ‘selection’ of the desired vector constructs. Thus we generated a series of cosmids containing the adeno helper dependent (HD) backbone in which we inserted cis‐ and trans‐acting tetracycline (tet) elements for the regulation of any gene of interest. One of these cosmids has been used to produce an HD adenovirus carrying a tetracycline‐regulated gene expressing β‐galactosidase.

Results

We have demonstrated that the adeno‐cosmid system allows rapid and efficient cloning of genes of interest in helper dependent vectors, and described a prototype ‘ready‐to‐use’ vector in which any gene of interest can be easily expressed under the control of the tet system. The HD viruses produced with this novel methodology can be grown at high titers, can be easily separated from the helper adenovirus, and allow delivery and regulated gene expression in a variety of tissues.

Conclusions

Exploiting the λ‐packaging system, complex adeno constructs can be generated with a simple and reproducible protocol, which allows selection of the desired size construct, counterselecting for the frequently observed intramolecular recombinations and deletions. Copyright © 2002 John Wiley & Sons, Ltd.

     

光敏色素与转录因子结合直接调控植物基因表达和发育

植物的光控发育一直是植物学中一个非常活跃的研究领域,是近该领域又取得重大突破性进展,人们通过酵母双杂交技术克隆到在体内与光敏色素相互作用的转录因子,并证实被光活化的光敏色素直接进入细胞核与转录因子结构合启动基因表达,本文就此研究进展作简要介绍。     

Developmentally regulated gene expression in Artemia: Histone gene expression in newly hatched larvae

The synthesis of histones and presence of histone mRNA sequences in embryos and larvae of the brine shrimp, Artemia, were investigated. Radiolabeling of proteins synthesized in vivo followed by electrophoretic and fluorographic analysis confirmed the prediction that histone synthesis is coordinated with the wave of DNA replication in newly hatched larvae. No histone synthesis occurs during development of encysted embryos. Hybridization of cloned Artemia histone gene DNA to total cell RNA indicated that dormant encysted embryos do not contain “masked” messenger RNA.