用薯类作检测生物组织中糖类和淀粉的材料

介绍了本地常见的一些薯类作为高中生物实验中检测生物组织的糖类和淀粉的材料。     

FLOURY ENDOSPERM6 encodes a CBM48 domain‐containing protein involved in compound granule formation and starch synthesis in rice endosperm

Starch is the most widespread form of energy storage in the plant kingdom. Although many enzymes and related factors have been identified for starch biosynthesis, unknown players remain to be identified, given that it is a complicated and sophisticated process. The endosperm of rice (Oryza sativa) has been used for the study of starch synthesis. Here, we report the cloning and characterization of the FLOURY ENDOSPERM6 (FLO6) gene in rice. In the flo6 mutant, the starch content is decreased and the normal physicochemical features of starch are changed. Significantly, flo6 mutant endosperm cells show obvious defects in compound granule formation. Map‐based cloning showed that FLO6 encodes a protein of unknown function. It harbors an N–terminal transit peptide that ensures its correct localization and functions in the plastid, and a C–terminal carbohydrate‐binding module 48 (CBM48) domain that binds to starch. Furthermore, FLO6 can interact with isoamylase1 (ISA1) both in vitro and in vivo, whereas ISA1 does not bind to starch directly. We thus propose that FLO6 may act as a starch‐binding protein involved in starch synthesis and compound granule formation through a direct interaction with ISA1 in developing rice seeds. Our data provide a novel insight into the role of proteins with the CBM48 domain in plant species.     

A Mediator of Rho-dependent Invasion Moonlights as a Methionine Salvage Enzyme

RhoA controls changes in cell morphology and invasion associated with cancer phenotypes. Cell lines derived from melanoma tumors at varying stages revealed that RhoA is selectively activated in cells of metastatic origin. We describe a functional proteomics strategy to identify proteins regulated by RhoA and report a previously uncharacterized human protein, named “mediator of RhoA-dependent invasion (MRDI),” that is induced in metastatic cells by constitutive RhoA activation and promotes cell invasion. In human melanomas, MRDI localization correlated with stage, showing nuclear localization in nevi and early stage tumors and cytoplasmic localization with plasma membrane accentuation in late stage tumors. Consistent with its role in promoting cell invasion, MRDI localized to cell protrusions and leading edge membranes in cultured cells and was required for cell motility, tyrosine phosphorylation of focal adhesion kinase, and modulation of actin stress fibers. Unexpectedly MRDI had enzymatic function as an isomerase that converts the S-adenosylmethionine catabolite 5-methylribose 1-phosphate into 5-methylribulose 1-phosphate. The enzymatic function of MRDI was required for methionine salvage from S-adenosylmethionine but distinct from its function in cell invasion. Thus, mechanisms used by signal transduction pathways to control cell movement have evolved from proteins with ancient function in amino acid metabolism.Cutaneous malignant melanoma has doubled in incidence over the past 30 years. Stages involved in progression of melanocytes to melanoma based on clinical and histopathological features include nontumorigenic nevi, dysplastic or atypical nevi, primary radial growth phase and vertical growth phase melanoma, and metastatic melanoma (1). Metastatic melanomas are often resistant to treatment; therefore therapeutic strategies require a more complete understanding of molecular determinants of this disease, particularly those involved in the invasive phenotype (2).Rho GTPases control a wide range of cellular responses including cell movement, morphogenesis, and coordinated migration (3). These pathways are implicated in malignant cell transformation and metastasis based on in vitro evidence showing tumorigenic and invasive responses to enhanced signaling in cell lines. Studies have demonstrated that overexpression of RhoC enhances invasion and metastasis in mouse xenografts of human melanoma and lung cancer cell lines (4, 5). In addition, some human tumors show elevated expression of Rho GTPases and exchange factors and/or reduced expression of GTPase-activating factors (6–8). Signaling through RhoA promotes actin polymerization and stress fiber formation, providing cells with contractile force needed for cell movement. Rho-GTP interacts with various effectors, including Rho-activated kinase, which promotes actin-myosin assembly via phosphorylation of myosin light chain phosphatase (9), or diaphanous-related formins, which nucleate actin filaments and stabilize microtubules (10, 11). Studies of cultured melanoma cells have revealed an “amoeboid” invasion mechanism involving RhoA-dependent Rho-activated kinase activation and inactivation of Rac (12, 13).RhoA also controls the formation and turnover of focal adhesion contacts, which mediate interactions between extracellular matrix and the actin cytoskeleton (14, 15). Signaling involves activation of Src and focal adhesion kinase (FAK)¹ and subsequent tyrosine phosphorylation of proteins recruited to integrin receptor complexes (16). Embryonic cells from FAK^−/− mice lose motility and cannot be rescued with FAK harboring a Y397F autophosphorylation site mutation not because they fail to form focal adhesions but because they are unable to disassemble focal adhesions (17). Thus, Rho controls cell movement by modulating the turnover of focal adhesion complexes via FAK. However, the mechanisms by which Rho GTPases control FAK are incompletely understood.In this study, we report that RhoA was constitutively activated in melanoma cells in a stage-specific pattern with elevated activity in cells from metastatic tumors. We present a functional proteomics screen for molecular targets of RhoA from which we identified a previously uncharacterized human protein induced in response to constitutive RhoA activation. This protein promoted Rho-dependent cell invasion and cell motility and provided a novel link for regulation of FAK tyrosine phosphorylation by RhoA. Thus, we refer to it as “mediator of Rho-dependent invasion (MRDI).” Although human MRDI has not been studied previously, it shows close sequence similarity to a methylthioribose-1-phosphate isomerase, which functions in methionine salvage pathways characterized in bacteria and yeast. We demonstrated that MRDI indeed has methylthioribose-1-phosphate isomerase activity and is required for methionine salvage in human cells. We further demonstrated that the catalytic activity of MRDI is independent of its role in cell invasion. Thus, MRDI is a dual function protein with promiscuous roles both as a metabolic enzyme and as an effector of signaling and cancer cell invasion.     

Characterization and comparative analyses of zebrafish intelectins: Highly conserved sequences,diversified structures and functions

Intelectin family, also called the X-lectin family, is a newly discovered gene family involved in development and innate immunity. However, no research was carried out for this gene family in the model organism zebrafish. Here we present the first characterization of seven zebrafish intelectins (zINTLs) and the first systematic comparative analysis of intelectins from various species in order to provide some clues to the function and evolution of this gene family. We examined the expression patterns of zINTLs in various development stages, normal adults, and Aeromonas salmonicida infected adults. Results showed that zINTL1–3 were highly expressed in one or several adult tissues. zINTL4–7, however, were expressed at quite low levels both in adults and various development stages, and some of them showed relaxation of functional constrains as revealed by K_a/K_s calculation. Of the seven zINTLs, zINTL3 was expressed predominantly in the liver and highly up-regulated upon infection, suggesting its important roles in immunity. Based on the characterization of zebrafish intelectins, we then conducted a systematic survey of intelectin members in various species and made comparative analyses. We found out that intelectin family may be a deuterostome specific gene family; and their expression patterns, quaternary structures and glycosylations vary considerably among various species, though their sequences are highly conserved. Moreover, these varied features have evolved multiple times independently in different species, resulting in species-specific protein structures and expression patterns.     

Antiparallel four-stranded coiled coil specified by a 3-3-1 hydrophobic heptad repeat

Coiled-coil sequences in proteins commonly share a seven-amino acid repeat with nonpolar side chains at the first (a) and fourth (d) positions. We investigate here the role of a 3-3-1 hydrophobic repeat containing nonpolar amino acids at the a, d, and g positions in determining the structures of coiled coils using mutants of the GCN4 leucine zipper dimerization domain. When three charged residues at the g positions in the parental sequence are replaced by nonpolar alanine or valine side chains, stable four-helix structures result. The X-ray crystal structures of the tetramers reveal antiparallel, four-stranded coiled coils in which the a, d, and g side chains interlock in a combination of knobs-into-knobs and knobs-into-holes packing. Interfacial interactions in a coiled coil can therefore be prescribed by hydrophobic-polar patterns beyond the canonical 3-4 heptad repeat. The results suggest that the conserved, charged residues at the g positions in the GCN4 leucine zipper can impart a negative design element to disfavor thermodynamically more stable, antiparallel tetramers.     

The polygalacturonase gene BcMF2 from Brassica campestris is associated with intine development

Brassica campestris Male Fertility 2 (BcMF2) is a putative polygalacturonase(PG) gene previously isolated from the flower bud of Chinesecabbage (Brassica campestris L. ssp. chinensis Makino, syn.B. rapa ssp. chinensis). This gene was found to be expressedspecifically in tapetum and pollen after the tetrad stage ofanther development. Antisense RNA technology was used to studythe function of BcMF2 in Chinese cabbage. Scanning and transmissionelectron microscopy revealed that there were deformities inthe transgenic mature pollen grains such as abnormal locationof germinal furrows. In addition, the homogeneous pectic exintinelayer facing the exterior seemed to be overdeveloped and predominantlyoccupied the intine, thus reversing the normal proportionaldistribution of the internal endintine layer and the externalexintine layer. Since it is a continuation of the intine layer,the pollen tube wall could not grow normally. This resultedin the formation of a balloon-like swelling structure in thepollen tube tip in nearly 80% of the transgenic pollen grains.Premature degradation of tapetum was also found in these transgenicplants, which displayed decreased expression of the BcMF2 gene.BcMF2 might therefore encode a new PG with an important rolein pollen wall development, possibly via regulation of pectin'sdynamic metabolism. Key words: Brassica campestris, Brassica rapa, Chinese cabbage, intine, PG, polygalacturonase, pollen wall Received 28 August 2008; Revised 14 October 2008 Accepted 20 October 2008     

Long-Term In Vivo Imaging of Multiple Organs at the Single Cell Level

Two-photon microscopy has enabled the study of individual cell behavior in live animals. Many organs and tissues cannot be studied, especially longitudinally, because they are located too deep, behind bony structures or too close to the lung and heart. Here we report a novel mouse model that allows long-term single cell imaging of many organs. A wide variety of live tissues were successfully engrafted in the pinna of the mouse ear. Many of these engrafted tissues maintained the normal tissue histology. Using the heart and thymus as models, we further demonstrated that the engrafted tissues functioned as would be expected. Combining two-photon microscopy with fluorescent tracers, we successfully visualized the engrafted tissues at the single cell level in live mice over several months. Four dimensional (three-dimensional (3D) plus time) information of individual cells was obtained from this imaging. This model makes long-term high resolution 4D imaging of multiple organs possible.     

QTL mapping of powdery mildew resistance in WI 2757 cucumber (Cucumis sativus L.)

Powdery mildew (PM) is a very important disease of cucumber (Cucumis sativus L.). Resistant cultivars have been deployed in production for a long time, but the genetic mechanisms of PM resistance in cucumber are not well understood. A 3-year QTL mapping study of PM resistance was conducted with 132 F_2:3 families derived from two cucumber inbred lines WI 2757 (resistant) and True Lemon (susceptible). A genetic map covering 610.4 cM in seven linkage groups was developed with 240 SSR marker loci. Multiple QTL mapping analysis of molecular marker data and disease index of the hypocotyl, cotyledon and true leaf for responses to PM inoculation identified six genomic regions in four chromosomes harboring QTL for PM resistance in WI 2757. Among the six QTL, pm1.1 and pm1.2 in chromosome 1 conferred leaf resistance. Minor QTL pm3.1 (chromosome 3) and pm4.1 (chromosome 4) contributed to disease susceptibility. The two major QTL, pm5.1 and pm5.2 were located in an interval of ~40 cM in chromosome 5 with each explaining 21.0–74.5 % phenotypic variations. Data presented herein support two recessively inherited, linked major QTL in chromosome 5 plus minor QTL in other chromosomes that control the PM resistance in WI 2757. The QTL pm5.2 for hypocotyl resistance plays the most important role in host resistance. Multiple observations in the same year revealed the importance of scoring time in the detection of PM resistance QTL. Results of this study provided new insights into phenotypic and genetic mechanisms of powdery mildew resistance in cucumber.     

OsVPS9A Functions Cooperatively with OsRAB5A to Regulate Post-Golgi Dense Vesicle-Mediated Storage Protein Trafficking to the Protein Storage Vacuole in Rice Endosperm Cells

In the rice endosperm cells, glutelins are synthesized on rough endoplasmic reticulum as proglutelins and are sorted to the protein storage vacuoles （PSVs） called protein body IIs （PBIIs）, where they are converted to the mature forms. Dense vesicle （DV）-mediated trafficking of proglutelins in rice seeds has been proposed, but the post-Golgi control of this process is largely unknown. Whether DV can fuse directly with PSV is another matter of debate. In this study, we propose a regulatory mechanism underlying DV-mediated, post-Golgi proglutelin trafficking to PBII （PSV）. gpa2, a loss- of-function mutant of OsVPS9A, which encodes a GEF of OsRAB5A, accumulated uncleaved proglutelins. Proglutelins were mis-targeted to the paramural bodies and to the apoplast along the cell wall in the form of DVs, which led to a con- comitant reduction in PBII size. Previously reported gpal, mutated in OsRab5a, has a similar phenotype, while gpalgpa2 double mutant exacerbated the conditions. In addition, OsVPS9A interacted with OsRAB5A in vitro and in vivo. We con- cluded that OsVPS9A and OsRAB5A may work together and play a regulatory role in DV-mediated post-Golgi proglutelin trafficking to PBII （PSV）. The evidence that DVs might fuse directly to PBII （PSV） to deliver cargos is also presented.     

A quantum theory for the irreplaceable role of docosahexaenoic acid in neural cell signalling throughout evolution

Six hundred million years ago, the fossil record displays the sudden appearance of intracellular detail and the 32 phyla. The “Cambrian Explosion” marks the onset of dominant aerobic life. Fossil intracellular structures are so similar to extant organisms that they were likely made with similar membrane lipids and proteins, which together provided for organisation and specialisation. While amino acids could be synthesised over 4 billion years ago, only oxidative metabolism allows for the synthesis of highly unsaturated fatty acids, thus producing novel lipid molecular species for specialised cell membranes.Docosahexaenoic acid (DHA) provided the core for the development of the photoreceptor, and conversion of photons into electricity stimulated the evolution of the nervous system and brain. Since then, DHA has been conserved as the principle acyl component of photoreceptor synaptic and neuronal signalling membranes in the cephalopods, fish, amphibian, reptiles, birds, mammals and humans. This extreme conservation in electrical signalling membranes despite great genomic change suggests it was DHA dictating to DNA rather than the generally accepted other way around.We offer a theoretical explanation based on the quantum mechanical properties of DHA for such extreme conservation. The unique molecular structure of DHA allows for quantum transfer and communication of π-electrons, which explains the precise depolarisation of retinal membranes and the cohesive, organised neural signalling which characterises higher intelligence.