The Translational Apparatus of Plastids and Its Role in Plant Development

Chloroplasts （plastids） possess a genome and their own machinery to express it. Translation in plastids occurs on bacterial-type 70S ribosomes utilizing a set of tRNAs that is entirely encoded in the plastid genome. In recent years, the components of the chloroplast translational apparatus have been intensely studied by proteomic approaches and by reverse genetics in the model systems tobacco （plastid-encoded components） and Arabidopsis （nucleus-encoded components）. This work has provided important new insights into the structure, function, and biogenesis of chloroplast ribosomes, and also has shed fresh light on the molecular mechanisms of the translation process in plastids. In addition, mutants affected in plastid translation have yielded strong genetic evidence for chloroplast genes and gene products influencing plant develop- ment at various levels, presumably via retrograde signaling pathway（s）. In this review, we describe recent progress with the functional analysis of components of the chloroplast translational machinery and discuss the currently available evidence that supports a significant impact of plastid translational activity on plant anatomy and morphology.     

Diverse Roles of ERECTA Family Genes n Plant Development

Multiple receptor-like kinases （RLKs） enable intercellular communication that coordinates growth and development of plant tissues. ERECTA family receptors （ERfs） are an ancient family of leucine-rich repeat RLKs that in Arabidopsis consists of three genes： ERECTA, ERL1, and ERL2. ERfs sense secreted cysteine-rich peptides from the EPF/EPFL family and transmit the signal through a MAP kinase cascade. This review discusses the functions of ERfs in stomata development, in regulation of longitudinal growth of aboveground organs, during reproductive development, and in the shoot apical meristem. In addition the role of ERECTA in plant responses to biotic and abiotic factors is examined.     

Ubiquitination-mediated protein degradation and modification： an emerging theme in plant-microbe interactions

Post-translational modification is central to protein stability and to the naodulation of protein activity.Various types ofprotein modification,such as phosphorylation,methylation,acetylation,myristoylation,glycosylation,and ubiquitina-tion,have been reported.Among them,ubiquitination distinguishes itself from others in that most of the ubiquitinatedproteins are targeted to the 26S proteasome for degradation.The ubiquitin/26S proteasome system constitutes the majorprotein degradation pathway in the cell.In recent years,the importance of the ubiquitination machinery in the controlof numerous eukaryotic cellular functions has been increasingly appreciated.Increasing number of E3 ubiquitin ligasesand their substrates,including a variety of essential cellular regulators have been identified.Studies in the past severalyears have revealed that the ubiquitination system is important for a broad range of plant developmental processes andresponses to abiotic and biotic stresses.This review discusses recent advances in the functional analysis of ubiquitina-tion-associated proteins from plants and pathogens that play important roles in plant-microbe interactions.     

TRANSGENIC PLANTS EXPRESSING BACILLUS THURINGIENSIS DELTA-ENDOTOXINS

Commercial varieties of transgenic Bacillus thuringiensis (Bt) plants have been developed in many countries to control target pests. Initially, the expression of native Bt genes in plants was low due to mRNA instability, improper splicing, and post-translation modifications. Subsequently, modifications of the native Bt genes greatly enhanced expression levels. This is a review of the developments that made modem high-expression transgenic Bt plants possible, with an emphasis on the reasons for the low-level expression of native Bt genes in plant systems, and the techniques that have been used to improve plant expression of Bt toxin genes.     

BAK1 Directly Regulates Brassinosteroid Perception and BRI1 Activation

Plants utilize plasma membrane-localized receptor-like kinases （RLKs） to sense extracellular signals to coordinate growth, development, and innate immune responses. BAK1 regulates multiple signaling pathways acting as a co-receptor of several distinct ligand-binding RLKs. It has been debated whether BAK1 serves as an essential regulatory component or only a signal amplifier without pathway specificity. This issue has been clarified recently. Genetic and structural analyses indicated that BAK1 and its homologs play indispensible roles in mediating brassinosteroid （BR） signaling pathway by directly perceiving the ligand BR and activating the receptor of BR, BRII. The mechanism revealed by these studies now serves as a paradigm for how a pair of RLKs can function together in ligand binding and subsequent initiation of signaling.     

Plant mineral nutrient sensing and signaling

正As terrestrial plants are sessile organisms and therefore must directly deal with an often complex and changing environment,they have had to develop complex and elegant strategies to survive and thrive in the face of environmental stress.This is particularly true for plant adaptation to the soil environment,where essential mineral nutrients often are found at suboptimal levels and their concentrations can vary significantly,both spatially and temporally.Furthermore,plants also at times have to respond to excessively high and potentially toxic levels of essential nutrients,as well as toxic levels of nonessential metals and metalloids in the soil.Although plant mineral nutrition as a bona fide research discipline has a history of over 150 years,beginning with the pioneering work of Justus Von Liebieg and others in the mid‐1800’s,it is only very recently that researchers have begun to truly appreciate how sophisticated plants are with regards to the sensing of their mineral status and the maintaining of mineral homeostasis in     

Electron Tomography in Plant Cell Biology

This review focuses on the contribution of electron tomography-based techniques to our understanding of cellular processes in plant cells. Electron microscopy techniques have evolved to provide better three-dimensional resolution and improved preservation of the subcellular components. In particular, the combination of cryofixation/freeze substitution and electron tomography have allowed plant cell biologists to image organelles and macromolecular complexes in their native cellular context with unprecedented three-dimensional resolution （4-7 nm）. Until now, electron tomography has been applied in plant cell biology for the study of cytokinesis, Golgi structure and trafficking, formation of plant endosome/prevacuolar compartments, and organization of photosynthetic membranes. We discuss in this review the new insights that these tomographic studies have brought to the plant biology field.     

Water Supply Changes N and P Conservation in a Perennial Grass Leymus chinensis

Changes in precipitation can influence soil water and nutrient availability, and thus affect plant nutrient conservation strategies. Better understanding of how nutrient conservation changes with variations in water availability is crucial for predicting the potential influence of global climate change on plant nutrient-use strategy. Here, green-leaf nitrogen （N） and phosphorus （P） concentrations, N- and P-resorption proficiency （the terminal N and P concentration in senescent leaves, NRP and PRP, respectively）, and N- and P-resorption efficiency （the proportional N and P withdrawn from senescent leaves prior to abscission, NRE and PRE, respectively） of Leymus chinensis （Trin.） Tzveh, a typical perennial grass species in northern China, were examined along a water supply gradient to explore how plant nutrient conservation responds to water change. Increasing water supply at low levels （〈 9000 mL/year） increased NRP, PRP and PRE, but decreased green-leaf N concentration. It did not significantly affect green-leaf P concentration or NRE. By contrast, all N and P conservation indicators were not significantly influenced at high water supply levels （〉 9000 mL/year）. These results indicated that changes in water availability at low levels could affect leaf-level nutrient characteristics, especially for the species in semiarid ecosystems. Therefore, global changes in precipitation may pose effects on plant nutrient economy, and thus on nutrient cycling in the plant-soil systems.     

Big Roles of Small Kinases： The Complex Functions of Receptor-Like Cytoplasmic Kinases in Plant Immunity and Development

Plants have evolved a large number of receptor-like cytoplasmic kinases （RLCKs） that often functionally and physically associate with receptor-like kinases （RLKs） to modulate plant growth, development and immune responses. Without any apparent extracellular domain, RLCKs relay intracellular signaling often via RLK complex-mediated transphosphorylation events. Recent advances have suggested essential roles of diverse RLCKs in concert with RLKs in regulating various cellular and physiological responses. We summarize here the complex roles of RLCKs in mediating plant immune responses and growth regulation, and discuss specific and overlapping functions of RLCKs in transducing diverse signaling pathways.     

Receptor-Like Kinases in Plant Innate Immunity

Plants employ a highly effective surveillance system to detect potential pathogens, which is critical for the success of land plants in an environment surrounded by numerous microbes. Recent efforts have led to the identification of a number of immune receptors and components of immune receptor complexes. It is now clear that receptor-like kinases （RLKs） and receptor-like proteins （RLPs） are key pattern-recognition receptors （PRRs） for microbe- and plant-derived molecular patterns that are associated with pathogen invasion. RLKs and RLPs involved in immune signaling belong to large gene families in plants and have undergone lineage specific expansion. Molecular evolution and population studies on phytopathogenic molecular signatures and their receptors have provided crucial insight into the co-evolution between plants and pathogens.     

Involvement of Histone Modifications in Plant Abiotic Stress Responses

As sessile organisms, plants encounter various environmental stimuli including abiotic stresses during their lifecycle. To survive under adverse conditions, plants have evolved intricate mechanisms to ...     

Notes from the Underground： Receptor-Like Kinases in Arabidopsis Root Development

During plant development, the frequency and context of cell division must be controlled, and cells must differentiate properly to perform their mature functions. In addition, stem cell niches need to be maintained as a reservoir for new cells. All of these processes require intercellular signaling, whether it is a cell relaying its position to other cells, or more mature cells signaling to the stem cell niche to regulate the rate of growth. Receptor-like kinases have emerged as a major component in these diverse roles, especially within the Arabidopsis root. In this review, the functions of receptor-like kinase signaling in regulating Arabidopsis root development will be examined in theareas of root apical meristem maintenance, regulation of epidermal cell fate, lateral root development and vascular differentiation.     

Ligand Perception,Activation, and Early Signaling of Plant Steroid Receptor Brassinosteroid Insensitive

Leucine-rich repeat receptor-like kinases （LRR-RLKs） belong to a large group of cell surface proteins involved in many aspects of plant development and environmental responses in both monocots and dicots. Brassinosteroid insensitive 1 （BRI1）, a member of the LRR X subfamily, was first identified through several forward genetic screenings for mutants insensitive to brassinosteroids （BRs）, which are a class of plant-specific steroid hormones. Since its identification, BRI1 and its homologs had been proved as receptors perceiving BRs and initiating BR signaling. The co-receptor BRIl-associated kinase 1 and its homologs, and other BRI1 interacting proteins such as its inhibitor BRI1 kinase inhibitor I （BKI1） were identified by genetic andbiochemical approaches. The detailed mechanisms of BR perception by BRI1 and the activation of BRI1 receptor complex have also been elucidated. Moreover, several mechanisms for termination of the activated BRI1 signaling were also discovered. In this review, we will focus on the recent advances on the mechanism of BRI1 phosphorylation and activation, the regulation of its receptor complex, the structure basis of BRI1 ectodomain and BR recognition, its direct substrates, and the termination of the activated BRI1 receptor complex.     

Structure-function Aspects of Extracellular Leucine-rich Repeat-containing Cell Surface Receptors in Plants

Plants exploit several types of cell surface receptors for perception of extracellular signals, of which the extracellular leucine-rich repeat （eLRR）-containing receptors form the major class. Although the function of most plant eLRR receptors remains unclear, an increasing number of these receptors are shown to play roles in innate immunity and a wide variety of developmental processes. Recent efforts using domain swaps, gene shuffling analyses, site-directed mutagenesis, interaction studies, and crystallographic analyses resulted in the current knowledge on ligand binding and the mechanism of activation of plant eLRR receptors. This review provides an overview of eLRR receptor research, specificallysummarizing the recent understanding of interactions among plant eLRR receptors, their co-receptors and corresponding ligands. The functions of distinct eLRR receptor domains, and their role in structure, ligand perception and multimeric complex formation are discussed.     

Improved detectability of microcirculatory dynamics by laser speckle flowmetry

Mechanisms of renal autoregulation generate oscillations in arterial blood flow at several characteristic frequencies. Full‐field laser speckle flowmetry provides a real‐time imaging of superficial blood microcirculation. The possibility to detect changes in oscillatory dynamics is an important issue in biomedical applications. In this paper we show how laser power density affects quality of the recorded signal and improves detectability of temporal changes in microvascular perfusion.

     

Hyperspectral imaging in medicine: image pre‐processing problems and solutions in Matlab

The paper presents problems and solutions related to hyperspectral image pre‐processing. New methods of preliminary image analysis are proposed. The paper shows problems occurring in Matlab when trying to analyse this type of images. Moreover, new methods are discussed which provide the source code in Matlab that can be used in practice without any licensing restrictions.

The proposed application and sample result of hyperspectral image analysis.     

Dual‐polarization Raman spectral imaging to extract overlapping molecular fingerprints of living cells

Raman spectral imaging is gaining more and more attention in biological studies because of its label‐free characteristic. However, the discrimination of overlapping chemical contrasts has been a major challenge. In this study, we introduce an optical method to simultaneously obtain two orthogonally polarized Raman images from a single scan of the sample. We demonstrate how this technique can improve the quality and quantity of the hyperspectral Raman dataset and how the technique is expected to further extend the horizons of Raman spectral imaging in biological studies by providing more detailed chemical information.

The dual‐polarization Raman images of a HeLa cell.