Metabolism and transport in non-photosynthetic plastids

Plastids in non-photosynthetic tissue are the site of fattyacid, starch and amino acid synthesis. The intermediates tosupport these activities are imported from the cytoplasm orgenerated by carbohydrate oxidation within the organelle. Thisreview considers the current understanding of the nature ofthe substrates which are transported into such plastids, theinteraction between pathways within the organelle which havea supply and demand relationship, and pathways which potentiallycompete for substrates. Key words: Non-photosynthetic plastids, metabolite transport, starch, fatty acids, nitrogen assimilation     

The light-dependent regulation of gene expression during plastid development in higher plants

In recent years there has been a considerable increase in our understanding of the manner by which light affects gene expression during chloroplast development. In most systems that have been studied, light acts through sensitive photoreceptor molecules and quantitatively increases or represses the level of expression of specific nuclear-and plastid-encoded genes. Although the mechanisms are obscure, a picture is beginning to emerge in which the coordination of nuclear and plastid gene expression is controlled by regulatory mechanisms originating within their respective subcellular compartments. This review summarizes some of our current knowledge concerning the nature of light-regulated gene expression in higher plants and provides a prospectus for future research in this area.     

高等植物赤霉素2-氧化酶基因的克隆、表达及其调控

赤霉素(GA)是一类重要的植物激素,对高等植物整个生命周期的生长发育起关键作用。调控赤霉素生物合成和代谢途径中的关键酶基因的表达可以控制植物体内赤霉素的含量。GA2-氧化酶是调节赤霉素合成和代谢的关键酶之一,使活性GA失活。本文主要对GA2-氧化酶基因的克隆、表达调控及其在植物基因工程中的应用等方面进行综述,为通过基因工程技术调控植物体内活性赤霉素的含量从而得到改良品种提供思路。     

MicroRNA regulation of gene expression in plants

It has only been a few years since we began to appreciate that microRNAs provide an unanticipated level of gene regulation in both plants and metazoans. The high level of complementarity between plant microRNAs and their target mRNAs has allowed rapid progress towards the elucidation of their varied biological functions. MicroRNAs have been shown to regulate diverse developmental processes, including organ separation, polarity, and identity, and to modulate their own biogenesis and function. Recently, they have also been implicated in some processes outside of plant development.     

Sugar regulation of gene expression in plants

The molecular details of sugar sensing and sugar-mediated signal transduction pathways are unclear but recent results suggest that hexokinase functions as an important plant sugar sensor in a way that is similar to that found in yeast. The use of mutants in Arabidopsis defective in specific signaling steps is of particular importance because these give access to the genes encoding components in the signaling pathways. In addition, the physiological analysis of such mutants may reveal the interaction of sugar-induced signaling pathways and those induced by other stimuli such as environmental or biotic stress.     

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.