OBPC Symposium: Maize 2004 &; beyond—Plant virus-based vectors in agriculture and biotechnology

Summary The study of plant viruses and their interaction with the plant host has contributed greatly to our understanding of plant biology. The recent development of plant viruses as transient expression vectors has not only enhanced our understanding of virus biology and antiviral defense mechanisms in plants, but has also led to the use of plant viral-based vectors as tools for gene discovery and production of recombinant proteins in plants for control of human and animal diseases. An overview of the state-of-the-art of viral expression systems, is presented, as well as examples from our laboratory on their use in identifying nuclear targeting motifs on viroid molecules and development of therapeutic proteins for control of animal diseases.     

Model plant systems in salinity and drought stress proteomics studies: a perspective on Arabidopsis and Sorghum

More than a decade after the sequencing of its genome, Arabidopsis still stands as the epitome of a model system in plant biology. Arabidopsis proteomics has also taught us great lessons on different aspects of plant growth, development and physiology. Without doubt our understanding of basic principles of plant biology would not have been this advanced if it were not for knowledge gained using Arabidopsis as a model system. However, with the projections of global climate change and rapid population growth, it is high time we evaluate the applicability of this model system in studies aimed at understanding abiotic stress tolerance and adaptation, with a particular emphasis on maintaining yield under hot and dry environmental conditions. Because of the innate nature of sorghum's tolerance to drought and moderate tolerance to salinity stresses, we believe sorghum is the next logical model system in such studies amongst cereals. In this acute view, we highlight the importance of Arabidopsis as a model system, briefly discuss its potential limitations in drought and salt stress studies, and present our views on the potential usefulness of sorghum as a model system for cereals in drought and salinity stress proteomic studies.     

The integration of cell proliferation and growth in leaf morphogenesis

A number of recent publications have assessed the outcome on leaf development of targeted manipulation of cell proliferation. The results of these investigations have awakened interest in the long-standing debate in plant biology on the precise role of cell division in morphogenesis. Does cell proliferation drive morphogenesis (cell theory) or is it subservient to a mechanism which acts at the whole organ level to regulate morphogenesis (organismal theory)? In this review, the central role of growth processes (distinct from cell proliferation) in morphogenesis is highlighted and the limitations in our understanding of the basic mechanisms of plant growth control are highlighted. Finally, an attempt is made to demonstrate how sequential local co-ordination of growth might provide an interpretation of some of the recent observations on cell proliferation and leaf morphogenesis.     

The excitability of plant cells: With a special emphasis on characean internodal cells

This review describes the basic principles of electrophysiology using the generation of an action potential in characean internodal cells as a pedagogical tool. Electrophysiology has proven to be a powerful tool in understanding animal physiology and development, yet it has been virtually neglected in the study of plant physiology and development. This review is, in essence, a written account of my personal journey over the past five years to understand the basic principles of electrophysiology so that I can apply them to the study of plant physiology and development. My formal background is in classical botany and cell biology. I have learned electrophysiology by reading many books on physics written for the lay person and by talking informally with many patient biophysicists. I have written this review for the botanist who is unfamiliar with the basics of membrane biology but would like to know that she or he can become familiar with the latest information without much effort. I also wrote it for the neurophysiologist who is proficient in membrane biology but knows little about plant biology (but may want to teach one lecture on “plant action potentials”). And lastly, I wrote this for people interested in the history of science and how the studies of electrical and chemical communication in physiology and development progressed in the botanical and zoological disciplines.     

A special issue on ＂Plant Molecular Biology＂

The use of molecular biology and genomics tools in plant biology research has greatly expanded our understandingof the molecular mechanisms that underlie plant development and physiology.The successful establishment of researchresources such as mutant populations has led to progress in a variety of fields,including plant reproductive develop-ment,signal transduction,hormone functions,defense responses and epigenetic control.In the future these advanceswill potentially facilitate crop improvement through molecular breeding.     

Plant hormones: metabolism, signaling and crosstalk

Plants synthesize various hormones in response to environmental cues and developmental signals to ensure their proper growth and development.Elucidation of the molecular mechanisms by which plant hormones control growth and development contributes to our understanding of fundamental plant biology and provides tools to improve crops.Because of their critical roles in plant growth and development, plant hormones have been studied extensively since the early days of plant biology.     

Evolutionary and developmental studies of unifacial leaves in monocots: Juncus as a model system

An important objective in evolutionary developmental biology is to understand the molecular genetic mechanisms that have given rise to morphological diversity. Leaves in angiosperms generally develop as a flattened structure with clear adaxial–abaxial polarity. In monocots, however, a unifacial leaf has evolved in a number of divergent species, in which leaf blades consist of only the abaxial identity. The mechanism of unifacial leaf development has long been a matter of debate for comparative morphologists. However, the underlying molecular genetic mechanism remains unknown. Unifacial leaves would be useful materials for developmental studies of leaf-polarity specification. Moreover, these leaves offer unique opportunities to investigate important phenomena in evolutionary biology, such as repeated evolution or convergent evolution of similar morphological traits. Here we describe the potential of unifacial leaves for evolutionary developmental studies and present our recent approaches to understanding the mechanisms of unifacial leaf development and evolution using Juncus as a model system.     

Toward synthetic plant development

The ability to engineer plant form will enable the production of novel agricultural products designed to tolerate extreme stresses, boost yield, reduce waste, and improve manufacturing practices. While historically, plants were altered through breeding to change their size or shape, advances in our understanding of plant development and our ability to genetically engineer complex eukaryotes are leading to the direct engineering of plant structure. In this review, I highlight the central role of auxin in plant development and the synthetic biology approaches that could be used to turn auxin-response regulators into powerful tools for modifying plant form. I hypothesize that recoded, gain-of-function auxin response proteins combined with synthetic regulation could be used to override endogenous auxin signaling and control plant structure. I also argue that auxin-response regulators are key to engineering development in nonmodel plants and that single-cell -omics techniques will be essential for characterizing and modifying auxin response in these plants. Collectively, advances in synthetic biology, single-cell -omics, and our understanding of the molecular mechanisms underpinning development have set the stage for a new era in the engineering of plant structure.

Recent advances in our understanding of plant development and ability to control gene expression in plants may enable a new strategy for engineering plant form and function.     

Rapid, transient expression of fluorescent fusion proteins in tobacco plants and generation of stably transformed plants

Expression and tracking of fluorescent fusion proteins has revolutionized our understanding of basic concepts in cell biology. The protocol presented here has underpinned much of the in vivo results highlighting the dynamic nature of the plant secretory pathway. Transient transformation of tobacco leaf epidermal cells is a relatively fast technique to assess expression of genes of interest. These cells can be used to generate stable plant lines using a more time-consuming, cell culture technique. Transient expression takes from 2 to 4 days whereas stable lines are generated after approximately 2 to 4 months.     

Laws of biology: why so few?

Finding fundamental organizing principles is the current intellectual front end of systems biology. From a hydrogen atom to the whole cell level, organisms manage massively parallel and massively interactive processes over several orders of magnitude of size. To manage this scale of informational complexity it is natural to expect organizing principles that determine higher order behavior. Currently, there are only hints of such organizing principles but no absolute evidences. Here, we present an approach as old as Mendel that could help uncover fundamental organizing principles in biology. Our approach essentially consists of identifying constants at various levels and weaving them into a hierarchical chassis. As we identify and organize constants, from pair-wise interactions to networks, our understanding of the fundamental principles in biology will improve, leading to a theory in biology.     

What is the role of cell division in leaf development?

An idea underlying a great deal of research and discussion in plant cell and developmental biology is that the spatial regulation of cell division plays a key role in plant development. In this article, the role of cell division in two aspects of leaf development is analysed: morphogenesis (leaf initiation, growth, and the generation of leaf shape) and histogenesis (the differentiation of leaf cells to form the various cell types that make up a functional leaf). The point of view that emerges from this analysis is that the rate and pattern of cell division is important for leaf development, but does not dictate leaf size, shape, or cell fate.     

Synthetic biology: a new approach to study biological pattern formation

The principles and molecular mechanisms underlying biological pattern formation are difficult to elucidate in most cases due to the overwhelming physiologic complexity associated with the natural context. The understanding of a particular mechanism, not to speak of underlying universal principles, is difficult due to the diversity and uncertainty of the biological systems. Although current genetic and biochemical approaches have greatly advanced our understanding of pattern formation, the progress mainly relies on experimental phenotypes obtained from time-consuming studies of gain or loss of function mutants. It is prevailingly considered that synthetic biology will come to the application age, but more importantly synthetic biology can be used to understand the life. Using periodic stripe pattern formation as a paradigm, we discuss how to apply synthetic biology in understanding biological pattern formation and hereafter foster the applications like tissue engineering.     

The mechanism of leaf morphogenesis

Whether cell division is a driving force in plant morphogenesis has long been debated. In this review, the evidence for the existence of cell division-dependent and cell division-independent mechanisms of plant morphogenesis is discussed. The potential mechanisms themselves are then analysed, as is our understanding of the regulation of these mechanisms and how they are integrated into development, with particular emphasis on data arising from the investigation of leaf morphogenesis. The analysis indicates the existence of both cell division-dependent and cell division-independent mechanisms in leaf morphogenesis and highlights the importance of future investigations to unravel the co-ordination of these mechanisms.     

Comparative plant development: the time of the leaf?

A key problem in developmental biology is understanding the origin of morphological innovations. Comparative studies in plants with different leaf morphologies indicate that the developmental pathway defined by KNOTTED1-type homeodomain proteins could be involved in generating different leaf forms. The differential expression of regulatory proteins has emerged as an important factor in driving morphological innovations in the plant kingdom--an idea that is well supported by quantitative trait locus analyses.     

DNA methylation dynamics during germline development

DNA methylation plays essential homeostatic functions in eukaryotic genomes. In animals, DNA methylation is also developmentally regulated and, in turn, regulates development. In the past two decades, huge research effort has endorsed the understanding that DNA methylation plays a similar role in plant development, especially during sexual reproduction. The power of whole-genome sequencing and cell isolation techniques, as well as bioinformatics tools, have enabled recent studies to reveal dynamic changes in DNA methylation during germline development. Furthermore, the combination of these technological advances with genetics, developmental biology and cell biology tools has revealed functional methylation reprogramming events that control gene and transposon activities in flowering plant germlines. In this review, we discuss the major advances in our knowledge of DNA methylation dynamics during male and female germline development in flowering plants.     

荧光原位杂交技术及其在植物研究中的应用

荧光原位杂交(FISH)是20世纪生物学领域的一项新技术。FISH应用细胞遗传学和分子生物学的基本原理,作为架设细胞遗传学与分子生物学之间的桥梁,现已被广泛应用于植物学各方面的研究。本文就FISH的基本原理、技术发展及其在植物遗传育种、起源进化、染色体物理图谱构建方面的应用及发展趋势进行了综述。