Structure and Evolution of  Centromere/Kinetochore Complex

Summary: In this article the identity of centromere chromatin is discussed on the basis of recent opinions concerning the formation of neocentromeres; it seems that not DNA but centromeric proteins are involved in this process. The structure of centromere/kinetochore complexes in holocentric chromosomes is similar to that in monocentric ones. Centromeric DNA undergoes rapid divergence due to point mutations, insertions and deletions. Centromeric and kinetochore proteins – CENPs – are conserved, i.e. they display a high degree of homology between yeast and higher Eukaryota (animals and plants). Deficiency, lack or modifications of CENPs result in improper sister chromatids segregation during anaphase. Proteins of cohesion complex seem to be conserved, as well.

Key words: evolution of centromeric DNA and proteins, neocentromeres, centromere/kinetochore assembly.
 

Molecular Biology of Plants in Postgenomic Era

Summary:

Key words:
 

How Does a Cell Recognize Spatial Directions in its Development the Importance of Tensorial Quantities

Summary: The directional information may originate not only from gradients of scalar fields or other vectors, but also from tensors such as the tensor of mechanical stress (s) and the tensor of growth rate (w). A tensor (except for spherical) distinguishes in space three mutually orthogonal directions along which the tensor values are extremal. These are the Principal Directions (PDs) of the tensor. While a  vector specifies an orientation with a sense, the PD specifies only an orientation. However, the main difference between a vector and a tensor concerns symmetry; tensor has a mirror symmetry. PDs of the tensor s or/and w are manifested in: the cell wall arrangement in meristems (the pattern of periclines and anticlines); the orientation of plant cell divisions; the arrangement of trabeculae in the cancellous tissue of bones; and the behaviour of animal cells on elastic substrata. The PDs of the stress tensor are especially predestined to provide coordinate systems in embryo- and morphogenesis, because their trajectories in the growing body, usually curvilinear, are mutually orthogonal, and one of the PD_ss is orthogonal to the body surface. The  proportional relation between relative rate of volumetric growth and turgor pressure (above a yield threshold) with the extensibility of isotropic cell wall as the proportionality coefficient, is well known. When this proportionality is transferred on the tensor level, it gives the relation between the second order tensor of growth rate and the same rank tensor of stress in the cell wall. This relationship is mediated by a fourth-order tensor of anisotropic cell wall extensibility. The latter tensor is an array of mechanical parameters dependent on genetic information of the growing cells. This  relation on the tensor level shows that a particular field of stresses can lead to different forms of the growing body depending on the genetic information. The studies on  reorientation of cortical microtubules (cMT)  in epidermal cells allowed the author to draw following conclusions: the cMT reorientation cycle is rotationary instead of oscillatory; the angular velocity of the cycle depends on the orientation of cMTs with respect to PD_ss, in particular, the cycle jumps through one or two PD_ss; the cMT orientation depends on which of the PD_ss the cycle jumps through; the orientation of the PD_ss depends on the stress state in cell wall; the choice of the PD_s to be jumped through, either PD_max,s  or PD_min,s, depends on the auxin level.

Key words:  gene therapy, hematopoietic cells, viral vectors, nonviral vectors.
 

Auxin  –  the Communication Factor in the Process of Plant Supracellular Specialization

Summary: Auxin signalling processes provide mechanism integrating environmental effects and genetic programs into a system of morphogenetic information  for coordinated growth and development of the multicellular plant organism. Auxin controlled system of communication at various levels of plant body organization depends upon structural polarity of the individual cells (especially in the meristematic regions), which allows basipetal transport of this phytohormone. Nearly every week extends theknowledge concerning auxin signal perception and transduction at the cell molecular level. In spite of these very extensive research  programs there is still little progress in knowledge of the auxin regulated processes integrating the cellular and supracellular levels. For the discussion in this paper I selected only small group of papers concerning the molecular level of auxin regulation which otherwise are extensively reviewed in the world literature including the Polish authors. Instead, the attention has been focused upon the system of autocontrol by auxin of its own polar transport. In this aspect, there are included also some of our own last results obtained in the  Forest Botany Department SGGW, during just ended (but continued for many years before 2000) studies on the auxin polar transport in which we used small stem sections of large trees consisting only a single axial cell layer of the cambial region. This gave me a chance to present also few suggestions of future investigations concerning the possible molecular mechanisms responsible for oscillation of the cell polarity expression in auxin transport which can be useful in explaining formation and propagation of the discovered earlier supracellular auxin waves.

Key words:  auxin, control mechanism, polar transport.
 

Molecular Anatomy of Intercellular Junctions in the Brain Vascular Endothelium

Summary: In this article, the current knowledge on the distribution of important molecular components of interendothelial junctions – both tight junctions (TJs) and adherens junctions (AJs) – in the blood-brain barrier (BBB) type of microvascular network is presented. We applied immunogold procedure to ultrathin sections of brain samples obtained from mice, rats, and human and embedded at low temperature in hydrophilic resin Lowicryl K4M. The results of our observations performed with transmission electron microscopy (EM) are discussed and compared with findings of other authors. The main structures responsible for the barrier and fence functions of the BBB appear to be TJs. Nevertheless, our main attention is focused on the presence and distribution of both intrinsic, i.e. integral membrane (transmembrane) molecules such as occludin, claudins, and junctional adhesion molecules (JAM-1) in TJs, and cadherins in AJs, as well as peripheral molecules of both types of junctions, e.g. zonula occludens (ZO-1) proteins and catenins. The latter group of molecules connects transmembrane proteins with the endothelial cell cytoskeleton. A close spatial association of the TJ proteins with those of AJs indicates that both junctional types are intermingled in the BBB type of endothelium. The data presented suggest, that some TJ-specific, transmembrane proteins, especially occludin and claudin-5, together with the peripheral ZO-1 molecules can be used as sensitive markers of normal or disturbed functional state of the BBB.

Key words: blood-brain barrier, transmission electron microscopy, zonula occludens (ZO-1).
 

Immunological Mechanisms in Cancer and Likelihood of  their Use in Immunotherapy

Summary:  One of important mechanisms of immunosurveilance against cancer in human organism is presence of natural, monoclonal IgM antibodies in circulation. Immunosupression after viral infections or induced by cigarette smoking may concord the cancerogenesis. Moreover, the developing cancer itself develops immunological tolerance. The likelihood of  immunotherapy of cancer is directed on use of specific monoclonal antibodies to decrease the mass of the tumor and vaccinations to increase T lymphocyte clones cytotoxic against cancer cells.

Key words: antigen presentation, dendritic cells, immunological tolerance, theraphy.
 

Transgenic Plant Derived, Biologically Active Proteins for Immunotherapy of Minimal Residual Cancer

Summary: The early diagnosis, treatment and prevention of cancer recurrence are the major priorities in future oncology. An increasing number of cases are surgically cured as a result of early diagnosis and novel approaches to chemo and radiotherapy. However, a significant percentage of these patients will develop recurrent and/or metastatic disease. The prognosis for patients with metastatic breast, lung and colorectal cancers at diagnosis or as a cancer recurrence are poor. Thus, about fifty percent of high risk adenocarcinoma patients, dependent on tumor type and staging, will develop recurrent disease in 5 years. It is therefore hypothesized that improved adjuvant treatment will be of significant value for the treatment of minimal residual disease and prevention of cancer recurrence. Among the potential target antigens in lung, breast and colorectal cancers are: GA73-3 (EpCAM) antigen as defined by monoclonal antibody (MAb) CO17-1A, a blood group related oligosaccharide LewisY (LeY) defined by MAb BR55-2 and an Epithelial Growth Factor Receptor (EGFr) defined by MAb 425.  All three MAb’s  were the first murine antibodies shown to mediate ADCC with murine and human effector cells. Their IgG2a and IgG3  isotypes are highly active in CDC and ADCC and all effectively inhibit human tumor growth in xenografted nude mice. All three MAb’s were shown to be safe in a clinical setting. There is evidence that adjuvant immunotherapy in conventionally treated high risk patients can mediate micrometastatic tumor cell destruction and prevent adenocarcinoma recurrence. Passive immunotherapy may not be a sufficient approach to eradicate all tumor  cells for extended periods of time. We are therefore also developing  cancer vaccines based on the antigens defined by MAbs. The development of polypeptides that mimic oligosaccharides (LeY and LeX) is in  the advanced stages. We expect that these molecules used as vaccines will induce not only humoral but also strong cellular responses in high risk cancer patients. To address and expedite the production of reliable and efficacious  immunoproteins (antibodies and vaccines) modern, plant-based protein expression systems are used.

Key words: plant derived active proteins, immunotherapy, cancer.
 

Caveolin, Caveolae and Neoplastic Transformation

Summary: Caveolin family proteins are major component of plasma membrane microdomains called caveolae. Several lines of evidence suggest that caveolin-1 belongs to tumour suppressors. Thus down-regulation of caveolin-1 expression may be critical for neoplastic transformation. Paradoxically elevated level of caveolin-1 appears to be associated with malignant phenotype. These apparently contradictory results may reflect the relative importance of caveolin-1 in primary tumour formation and progression of the disease.

Keywords:  caveolin, caveolae, signal transduction, neoplastic transformation, progression and metastasis
 

Plant Genome Size

Summary: Genome size of angiosperms estimated for only 1.4% of species is highly variable. Comparison of small and large plant genomes has shown that differences in genome size can mainly be attributed to varying proportion of repeated DNA sequences though the number of genes is similar. The function of noncoding, repetitive sequences are controversial.  DNA amount is relatively constant and tends to be highly characteristic for a species but can change. Mechanisms of genome variation, especially genome size decrease is not clear. Molecular investigations indicated the significant role of retrotransposons in such process. Genome size is an important biodiversity character whose study provides a strong unifying element in basic biology and practical use.

Key words: C DNA, cytometry, endoredupliction,  repetitive sequences, genome size.
 

Holokinetic Chromosomes in Plants

Summary: The article concerns holokinetic (holocentric) chromosomes in plants. Holokinetic chromosomes posses diffuse kinetochore spread out through the length of the chromatids. Such kinetochore structure allows holokinetic chromosomes fuse (complete or partial symploidy) or undergo fragmentation (complete or partial agmatoploidy) with no influence on regular mitotic divisions (each chromosome fragment behaves as chromosome). Several aspects of holokinetic chromosomes are presented such as: structure of centromere/kinetochore complex, behavior of holokinetic chromosomes in meiosis and mitosis, structural chromosome mutations and genome mutations in vivo and in vitro (in callus cells obtained from different tissues of plants with holokinetic chromosomes). Additionally, nuclear DNA amount in relation to chromosome mutations (fusion, fission), numerical chromosome variation (aneuploidy sensu stricto) and genome mutations (total agmatoploidy with no DNA gain; total symploidy with no DNA loss; polyploidy accompanied by DNA multiplication) and discussed.

Key words: holokinetic chromosomes, centromere/kinetochore complex, structural chromosome mutations, polyploidy, nuclear DNA amount.

Programmed Cell Death  in Higher Plant Development

Summary: The term "programmed cell death" (PCD) defines a tightly genetically controlled process leading to cell destruction in eukaryotic organisms; the process is induced by endogenous or exogenous factors and proceeds due to molecular mechanisms that are triggered by the cell itself.  PCD is a definition broader than apoptosis. The latter term defines the programmed death of animal cells with a characteristic morphotype and internucleosomal cleavage of nDNA, which is the mean biochemical marker of the executive phase. Genetic mechanisms of PCD are markedly conserved during evolution of various groups of animals and the molecular PCD pathways have been described in detail. At present, the essential question is whether plants – when executing PCD – apply the same highly evolutionary conserved molecular mechanisms as the animal kingdom? The question is the more important that in the sequenced genome of Arabidopsis thaliana, no homologues were found of the key genes of the animal cell death program. Much present research concerns the cytological and molecular aspects of PCD in cells, tissues and organs, the PCD that takes place according to the developmental program of higher plants in the vegetative and generative phases. These experiments are carried out with the use of new techniques, in in vitro systems, and are aimed at identification of genes steering the PCD processes in plants. PCD is characterised by morphological features that result from reorganisation of the molecular and structural architecture of all cellular compartments. Plant and animal cells undergoing PCD differ in organisation, hence, no wonder that the morphotypes of PCD of various cell types show pronounced differences. Which cells and tissues undergo PCD in the development of an angiosperms plant? Does plant organ senescence involve PCD mechanisms? What is the relation between cell cycle and PCD? Is differentiation and polyploidization of plant cells the condition of entering the PCD pathway? Are mitochondria the causal factor in plant PCD? Does PCD always lead to complete destruction of the plant cell? Does PCD in the plant organism serve mainly the role of removing redundant, misplaced or damaged cells, as claimed by many authors? What is the role of growth and development regulators in coordination of PCD processes in the plant body? These are only some of the numerous questions which need to be discussed.

Key words:  programmed cell death (PCD), apoptosis, higher plants.
 

Cytochemistry in Plant Biotechnology –  Application Of ??-Glucuronidase (GUS) And Green Fluorescent Protein (GFP)-Based Reporter Systems

Summary: Genetic transformation of plants plays an important role in modern biotechnology.  Genetically modified plants attract attention not only as cultivated plants (vegetables, grain crops) but also as bioreactors for production of valuable secondary metabolites, and recombinant proteins which can be used as pharmaceuticals, vaccines, antibodies and diagnostic or industrial enzymes. Moreover, since the middle 90’ an extensive research has been done towards application of transgenic plants for phytoremediation technology. Several modern cytochemical techniques and methods are being used during both development of plant genetic transformation technologies as well as during their applications. Two reporter genes, uidA (gusA) and gfp, coding b-glucuronidase enzyme (GUS) and green fluorescent protein (GFP), respectively, are an example of utilization of cytochemical tools in plant biotechnology.

Key words:   b-glucuronidase, cytochemical techniques, GFP, GUS, plant biotechnology, plant genetic transformation, uidA
 

Mechanisms of Chromosome Condensation

Summary: Mitotic condensation and segregation of chromosomes represent two fundamental  processes ensuring the correct inheritance of the genomic DNA sequences replicated in the course of S-phase. Although Walther Fleming’s first drawings of mitosis in salamander cells have been published over 120 years ago, our current knowledge still does not consent to construct a universal model showing definitively how the mitotic chromosome is formed and partitioned. Molecular studies indicate that at least  three major classes of proteins take part in the composition of mitotic chromosomes: (1) the basic structural components of interphase chromatin such as core histones and histone H1, (2)  molecules that are present on both interphase and mitotic chromosomes but whose activities are used differently at particular phases of the cell division cycle, e.g. topoisomerase II, and (3) the complexes of cohesin and condensin, with the names given to indicate their roles in chromosome cohesion and compaction. All these proteins, in cooperation with other factors, contribute to the organization of the mitotic structure of chromosomes, without obvious need to exchange basic molecular components of interphase chromatin.

Key words:  chromosome condensation, mitosis, histone H1 and H3 phosphorylation, topoisomerase II, condensin
 

Changes in the Ultrastructure and Occurrence of Plasmodesmata Versus the Differentiation Process of the Chara Species Antheridia

Summary: Changes in the ultrastructure and occurrence of plasmodesmata in C. vulgaris and C. tomentosa antheridia development starting from the 24-celled stage till the formation of mature spermatozoids were described. These changes are closely correlated with particular differentiation stages and may indicate adaptation of plasmodesmata structure and function in cell-to-cell communication to the changing morphogenetic situation. A hypothesis has been put forward that symplasmic regulation mechanisms during development and functioning of plants have a general character.

Key words:  plasmodesmata ultrastructure, symplasmic isolation,  antheridia  differentiation, spermatogenesis, spermiogenesis, Chara,  gibberellins

Potential Protein Markers for Thyroid

Summary: Now, great interest is observed on studies directed toward characterization of potential molecular markers of malignant thyroid disorders. They seem to be of special value in diagnosis of follicular adenoma and carcinoma. In this review, general character-ization of thyroid lesions and potential promising markers for thyroid carcinomas, i.e., galectin-1 and -3, HMGA (HMGI/Y) proteins, thymosin b-10 and telomerase are described.

Key words:  thyroid tumors, galectin-1, galectin-3, HMGA (HMGI/Y) proteins, thymosin b-10, telomerase
 

Role of Zinc in the Modulation of Apoptosis

Summary: The review describes the current knowledge on zinc as modulator of apoptosis. This important trace element in divalent cation form has abilities both to inhibit and induce of apoptosis process. The commitment of Zn²⁺ to the regulation of programmed cell death still is not fully understood. It is suggested that Zn²⁺ may have multiple intracellular targets in the apoptotic signaling cascade. Zinc supplementation acts as an inhibitor of program-med cell death in many cells. At biochemical level zinc ions are involved in suppression/ /activation of endonuclease(s) which cause(s) apoptotic DNA fragmentation and also influenced on caspase activation. In some cell types zinc works as a possible trigger for apoptotic events associated with the breakdown of mitochondrial membrane potential with a subsequent release of reactive oxygen species.

Key words: apoptosis, zinc, endonucleases, DNA fragmentation, caspases, proteolysis, mitochondrial membrane potential, ROS

Heterotrimeric G Protein Signaling Pathway in Plants

Summary: T: In animals numerous extracellular signals specifically modify cell processes by specific receptors which activate different heterotrimeric G proteins. Activated G proteins are able to induce intracellular signaling pathways by activating effectors catalyzing production of secondary messengers. In plants only one or two proteins (and encoding genes) with properties characteristic of heterotrimeric G protein subunits (Ga, Gb and Gg) were discovered. Although no association in heterotrimers was observed it can be hypothesized that few types of G protein heterotrimers may be involved in signal transduction. Some proteins whose receptor and effector functions must be evidenced were also identified. The knowledge concerning the course and role of G protein signaling pathway in plants is far from comprehensive. Description of this pathway calls for further, intensive studies which can be helped by the fact that pharmacological modification of G protein activity influences both fitohormones (and other signaling molecule) effects and numerous physiological processes. Mutants deprived of  Ga and Gb subunits as well as transformants with protein overexpression can broaden scientific approach.

Key words:  G protein pathway, GPCR, G protein effectors, plants