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Two cytotypes of ‘giant fescue’ sporting gametic chromosome number of n = 14 and n = 21 corresponding to 4x and 6x ploidy level (based on x = 7) were encountered in the various localities in India falling in the Western Himalayan region. The pollen mother cells of hexaploid cytotype also exhibited presence of B chromosomes (n = 21 + 0 − 2B). The intra-specific polyploidy had direct effect on both macro- and microscopic morphological traits. Cyto-geographically the 4x cytotype has wider distribution whereas 6x cytotype are scarcely represented.

La capacidad autorregenerativa de las células madre es una de sus principales propiedades, la cual ha sido utilizada en procesos de regeneración celular, ya sea para reemplazo o para recuperación celular de tejidos y órganos. Estas células también tienen la habilidad de producir diferentes compuestos farmacológicos y toxicológicos. Así mismo, gracias a sus propiedades antiinflamatorias, antifibróticas regenerativas y antimicrobianas, se sitúan como un recurso biológico interesante. El objetivo de este libro es profundizar en los procesos moleculares y celulares de las células madre y mostrar sus diferentes usos biotecnológicos.

Meiotic studies in two populations of Solanum sisymbrifolium were caried out in detail each from Railway track at Gaya railway station and from Lal Darwaja of Munger. Meiosis showed anomalies like multivalent and univalent at metaphase-I and soe pollen other cells showed abnormalities like clumping of chromosomes, precocious separation of chromosomes and translocation chains and rings while at anaphase-I,12:12chromosomes were recorded in most of the pollen mother cells. About 15% of the PMC at this stage were found to be abnormal.

This article presents the results of comparative studies of the frequency and distribution of chiasmata in pollen mother cells (PMCs) in five diploid tomato species, Solanum lycopersicum, S. pimpinellifolium, S. peruvianum, S. habrochaites, and S. neorickii, and one autotetraploid species, S. pimpinellifolium. It was established that under the same growing conditions, the total chiasma frequency in the cell depended on the species. At the same time, the green-fruited species S. peruvianum, S. neorickii, and S. habrochaites differed in distal chiasma frequency, while the red-fruited species S. lycopersicum and S. pimpinellifolium differed in interstitial chiasma frequency. It was shown that the total chiasma frequency in PMCs of plants of one species is a stable index of recombination potential that does not depend on the growing conditions. The redistribution between distal and interstitial chiasmata was found to be more variable, depending on the species, year, geographic growth conditions. In autotetraploid, the chiasma frequency per bivalent was lower than that in diploid S. pimpinellifolium plants, primarily due to interstitial chiasmata, the frequency of which remained at the level characteristic for diploid plants. It was concluded that the recombination plasticity of the tomato genomes was due to the redistribution of chiasmata along bivalents, and not to the change in their number in the cell.

La Universidad Autónoma de Bucaramanga (UNAB) se enorgullece de presentarles la revista A Ciencia Cierta, un bello y edificante ejemplo del compromiso con el conocimiento y el progreso de nuestro entorno. Tendremos las páginas abiertas para que todos nuestros investigadores y docentes les enseñen a los diversos estamentos de la sociedad los resultados de sus propuestas, experimentos, análisis concienzudos y procesos creativos en los diferentes terrenos del saber. Dos veces al año les estaremos entregando de manera gratuita una publicación de lujo que responda a los más elevados estándares y nos permita comunicar con un lenguaje cercano y un diseño agradable los logros no solo en ámbitos puros y duros como la medicina, la ingeniería, la tecnología o la economía –por citar algunos–, sino en otros como el derecho, las humanidades y las artes. 1 Editorial 3 2 De las cabañuelas al internet de las cosas en el campo 4 3 “Envidio la cultura colombiana de vivir feliz” 8 4 Las detectives del cáncer en Bucaramanga 12 5 Células madre para el pie diabético 18 6 La científica que quiere ver a los microbios limpiar el 22 planeta 7 Renacer tras la avalancha del Río de Oro 29 The Autonomous University of Bucaramanga (UNAB) is proud to present the magazine A Ciencia Cierta, a beautiful and edifying example of commitment to knowledge and progress in our environment. We will have the pages open for all our researchers and teachers to teach the various levels of society the results of their proposals, experiments, conscientious analysis and creative processes in the different fields of knowledge. Twice a year we will be giving you free of charge a luxury publication that meets the highest standards and allows us to communicate with a friendly language and a pleasant design the achievements not only in pure and hard fields such as medicine, engineering, technology or the economy –to name a few–, but in others such as law, the humanities and the arts.

Introducción y objetivo: La úlcera de pie diabético (UPD), es una complicación frecuente con alta carga de morbi-mortalidad en pacientes con Diabetes Mellitus (DM). La medicina regenerativa aparece como estrategia efectiva y segura en el tratamiento de la UPD. Nuestro objetivo fue evaluar el efecto terapéutico de los derivados acelulares de células madre mesenquimales (dac-MSCs), en UPD tipo 1 y tipo 2. Materiales y métodos: Se realizó un análisis secundario de los datos obtenidos del ensayo clínico realizado en Foscal Internacional. El Análisis de datos para cinética y velocidad de la UPD se hizo realizando una comparación entro los grupos experimentales mediante la prueba de ANOVA y mediante un post-test de comparación múltiple de Bonferroni. Se calculó además la función de sobrevida de la úlcera hasta su cierre al 50% y 100% mediante el método de Kaplan-Meier. Finalmente se realizó un análisis de cociente de riesgo (HR, por sus siglas en ingles) al cierre de la úlcera al 50% y al 100%. Resultados: El 60.7% de los participantes fueron hombres, la media de edad fue de 61.5 ± 7.8 años y al inicio del tratamiento el 75% los participantes presentaron una HbA1c fuera de metas (HbA1c > 7%). Tanto los pacientes con UPD tipo 1 como tipo 2, lograron un velocidad y cinética de cierra mayor en comparación con el grupo de terapia convencional. El análisis de sobrevida de la úlcera hasta el cierre al 50 y 100% de la UPD mostró mayor eficacia tanto en el grupo de dac-MSCs y células madre mesenquimales de medula ósea (BM-MSCs) en comparación con el grupo convencional. El cociente de riesgo (HR, por sus siglas en ingles), de cierre de las UPD al 50 y 100%, fue significamente mayor en pacientes tratados con dac-MSCs y BM-MSCs en comparación con el grupo de tratamiento convencional. Conclusiones: La medicina regenerativa (BM-MSCs y dac-MSCS), surge como una estrategia terapéutica efectiva y segura para el tratamiento de pacientes con UPD. 1. PLANTEAMIENTO Y JUSTIFICACIÓN DEL PROBLEMA .......................... 10 2. MARCO TEÓRICO .......................................................................................... 11 2.1. Diabetes Mellitus tipo 2: fisiopatología ............................................................. 11 2.2. Diabetes Mellitus tipo 2: epidemiología ............................................................ 12 2.3. Úlcera de pie diabético: fisiopatología ............................................................... 13 2.4. Úlcera de pie diabético: clasificación ................................................................ 15 2.5. Proceso de cicatrización de heridas ................................................................... 16 2.6. Tratamientos actuales ........................................................................................ 18 2.7. Células madre mesenquimales .......................................................................... 19 2.8. Mecanismos terapéuticos de las MSCs en lesiones cutáneas .............................. 20 2.9. Derivados acelulares de células madre mesenquimales (dacMSCs) en lesiones cutáneas ........................................................................................................................22 3. ESTADO DEL ARTE .......................................................................................22 4. PREGUNTA DE INVESTIGACIÓN ................................................................ 27 5. OBJETIVOS ..................................................................................................... 27 5.1 Objetivo general ................................................................................................ 27 5.2 Objetivos específicos ......................................................................................... 28 6. METODOLOGÍA ............................................................................................. 28 6.1 Tipo de estudio .................................................................................................. 28 6.2 Población .......................................................................................................... 28 6.3 Criterios de inclusión y exclusión ...................................................................... 28 6.4 Muestra y recolección de datos .......................................................................... 29 6.5 Hipótesis ............................................................................................................ 29 6.6 Variables ............................................................................................................ 30 6.7 Plan de análisis de datos ..................................................................................... 33 6.8 Consideraciones éticas ........................................................................................ 33 7. RESULTADOS ..................................................................................................33 7.1 Características demográficas de los participantes ............................................... 33 7.2 Evaluación del cierre de la úlcera de pie diabético tipo 1 ................................... 35 7 Protocolo V-01 – 26 de febrero 2020 7.3 Evaluación del cierre de la úlcera de pie diabético tipo 2 ................................... 37 7.4 Analisis de sobrevida de la UPD hasta el cierre: comparación entre los grupos dac-MSCs vs terapia convencional ................................................................................ 40 7.5 Analisis de sobrevida de la UPD hasta el cierre: comparación entre los grupos BM-MSCs vs terapia convencional ................................................................................ 41 7.6 Cociente de riesgo de cierre al 50% de las UPD y tasa de curación persona/día ................................................................................................................... 42 7.7 Cociente de riesgo de cierre al 100% de las UPD y tasa de curación persona/día ................................................................................................................... 43 8. DISCUSIÓN ...................................................................................................... 44 9. CONCLUSIONES ............................................................................................. 49 REFERENCIAS Especialización Introduction and objective: Diabetic foot ulcer (DFU) is a frequent complication with a high morbidity and mortality burden in patients with Diabetes Mellitus (DM). Regenerative medicine appears as an effective and safe strategy in the treatment of UPD. Our aim was to evaluate the therapeutic effect of acellular derivatives of mesenchymal stem cells (dac-MSCs) in type 1 and type 2 UPD. Materials and methods: A secondary analysis of the data obtained from the clinical trial conducted at Foscal International was performed. Data analysis for UPD kinetics and velocity was performed by comparing the experimental groups by ANOVA test and by Bonferroni's multiple comparison post-test. The survival function of the ulcer to closure at 50% and 100% was also calculated using the Kaplan-Meier method. Finally, a hazard ratio (HR) analysis was performed at ulcer closure at 50% and 100%. Results: 60.7% of the participants were men, the mean age was 61.5 ± 7.8 years and at the start of treatment 75% of the participants had an HbA1c outside the target range (HbA1c > 7%). Both type 1 and type 2 UPD patients achieved higher velocity and kinetics of closure compared to the conventional therapy group. Analysis of ulcer survival to closure at 50 and 100% UPD showed greater efficacy in both the dac-MSCs and bone marrow mesenchymal stem cells (BM-MSCs) group compared to the conventional group. The hazard ratio (HR) of 50 and 100% UPD closure was significantly higher in patients treated with dac-MSCs and BM-MSCs compared to the conventional treatment group. Conclusions: Regenerative medicine (BM-MSCs and dac-MSCS), emerge as an effective and safe therapeutic strategy for the treatment of patients with UPD.

The replicative aging of the budding yeast, Saccharomyces cerevisiae, has been a useful model for dissecting the molecular mechanisms of the aging process. Traditionally, the replicative lifespan (RLS) is measured by manually dissecting mother cells from daughter cells, which is a very tedious process. Since 2012, several microfluidic systems have been developed to automate the dissection process, significantly accelerating RLS determination. Here, we describe a detailed protocol of RLS measurement using a commercially available microfluidic system based on the HYAA chip design, which enables data collection of up to 8,000 cells in a single experiment.

Premise Counting chromosomes is a fundamental botanical technique, yet it is often intimidating and increasingly sidestepped. Once mastered, the basic protocol can be applied to a broad range of taxa and research questions. It also reveals an aspect of the plant genome that is accessible with only the most basic of resources-access to a microscope with 1000× magnification is the most limiting factor. Methods and results Here we provide a detailed protocol for choosing, staining, and squashing angiosperm pollen mother cells. The protocol is supplemented by figures and two demonstration videos. Conclusions The protocol we provide will hopefully demystify and reinvigorate a powerful and once commonplace botanical technique that is available to researchers regardless of their location and resources.

T6V#2S·6AL and T6V#4S·6DL translocation chromosomes developed from the cross of wheat and different Dasypyrum villosum accessions have good powdery mildew (PM) resistance, but their pairing and pyramiding behavior remains unclear. Results in this study indicated that the pairing frequency rate of the two differently originated 6VS chromosomes in their F 1 hybrid was 18.9% according to genomic in situ hybridization (GISH); the PM resistance plants in the F 2 generation from the cross between T6V#4S·6DL translocation line Pm97033 and its PM susceptible wheat variety Wan7107 was fewer than expected. However, the ratio of the resistant vs. the susceptible plants of 15:1 in the F 2 generation derived from the cross between the two translocation lines of T6V#2S·6AL and T6V#4S·6DL fitted well. Plants segregation ratio (homozygous:heterozygous:lacking) revealed by molecular marker for T6V#4S·6DL or T6V#2S·6AL in their F 2 populations fitted the expected values of 1:2:1 well, inferring that the pairing of the two alien chromosome arms facilitates the transmission of T6V#4S·6DL from the F 1 to the F 2 generation. A quadrivalent was also observed in 21% of pollen mother cells (PMCs) of homozygote plants containing the two pairs of translocated chromosomes. The chromosome pairing between 6V#2S and 6V#4S indicates that it will be possible to obtain recombinants and clarify if the PM resistance determinant on one alien chromosome arm is different from that on the other.

The yeast Hsp26 protein, a conserved a-crystallin small heatshock chaperone, is assembled in to oligomeric complexes, microscopically visible as distinct cytoplasmic foci. We studied at single cell resolution the dynamics of Hsp26p foci assembly, the mode of their inheritance in to progeny cells and the physiological significance of Hsp26p function. We showed that Hsp26p foci are formed upon cells' entry in to stationary phase, but upon re-entry to proliferation they are asymmetrically retained in the mother cells and are absent from the newborn daughters. Despite the fact that Hsp26p assists re-solubilization of aggregation-prone proteins it does not extend chronological life span nor does it increase the tolerance of either mother or daughters against lethal stresses. Upon sequential HSP26 inductions, newly synthesized Hsp26p is readily incorporated in pre-existing foci, generating larger in size, but similar in appearance foci. At extreme heat-shock conditions, Hsp26p foci break apart into smaller granules dispersed in both mothers and growing buds, while recovery at normal temperature results in Hsp26p foci reassembly. These results suggested that such a complicated mechanism of dynamic Hsp26p assembly and disassembly, as well as asymmetric segregation may contribute to fine tuning regulation of protein aggregates' refolding, cell fitness and survival.

Gas exchange between the plant and the atmosphere takes place through stomatal pores formed by paired guard cells. Grasses develop a unique stomatal structure that consists of two dumbbell-shaped guard cells flanked by lateral subsidiary cells. These structures confer a very efficient gas exchange capacity, which may have contributed to the evolutionary success of grasses. Recent works have identified orthologues of Arabidopsis MUTE in three grass species: BdMUTE in Brachypodium distachyon, BZU2/ZmMUTE in maize, and OsMUTE in rice. These genes induce the recruitment of subsidiary cells, and it appears to rely upon the ability of intercellular movement, from the guard mother cell to subsidiary mother cells, of the proteins encoded by them. Unexpectedly, this function of these grass MUTE genes contrasts with that of Arabidopsis MUTE, which promotes guard mother cell identity. These MUTE orthologues also appear to control guard mother cell fate progression, with the action of BdMUTE being less severe than those of BZU2/ZmMUTE and OsMUTE. The emerging picture unravels that grass MUTE genes have not only diverged, due to neo-functionalization, from Arabidopsis MUTE, but also among them.

Visualization of meiotic chromatin from pollen mother cells has become an essential technique to study meiosis in the model plant Arabidopsis thaliana. Here we present an advanced cytogenetic method that combines improved immunocytology with chromosome painting, thereby generating a tool to quantitatively analyze localization of proteins to any given genomic region. Proteins involved in different processes such as DNA double-strand break formation and recombinational repair can be visualized on meiotic chromatin with the additional feature of assessing their abundance at specific chromosomal locations.

Both gram-negative and gram-positive bacteria release extracellular vesicles (EVs) that contain components from their mother cells. Bacterial EVs are similar in size to mammalian-derived EVs and are thought to mediate bacteria–host communications by transporting diverse bioactive molecules including proteins, nucleic acids, lipids, and metabolites. Bacterial EVs have been implicated in bacteria–bacteria and bacteria–host interactions, promoting health or causing various pathologies. Although the science of bacterial EVs is less developed than that of eukaryotic EVs, the number of studies on bacterial EVs is continuously increasing. This review highlights the current state of knowledge in the rapidly evolving field of bacterial EV science, focusing on their discovery, isolation, biogenesis, and more specifically on their role in microbiota–host communications. Knowledge of these mechanisms may be translated into new therapeutics and diagnostics based on bacterial EVs.

Recently, efforts have been made to characterize the hallmarks that accompany and contribute to the phenomenon of aging, as most relevant for humans [1]. Remarkably, studying the finite lifespan of the single cell eukaryote budding yeast (recently reviewed in [2] and [3]) has been paramount for our understanding of aging. Here, we compile observations from literature over the past decades of research on replicatively aging yeast to highlight how the hallmarks of aging in humans are present in yeast. We find strong evidence for the majority of these, and summarize how yeast aging is especially characterized by the hallmarks of genomic instability, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, and mitochondrial dysfunction.

Recently, efforts have been made to characterize the hallmarks that accompany and contribute to the phenomenon of aging, as most relevant for humans [1]. Remarkably, studying the finite lifespan of the single cell eukaryote budding yeast (recently reviewed in [2] and [3]) has been paramount for our understanding of aging. Here, we compile observations from literature over the past decades of research on replicatively aging yeast to highlight how the hallmarks of aging in humans are present in yeast. We find strong evidence for the majority of these, and summarize how yeast aging is especially characterized by the hallmarks of genomic instability, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, and mitochondrial dysfunction.

Proyecto de Investigación (Código: 1510097) Instituto Tecnológico de Costa Rica. Vicerrectoría de Investigación y Extensión (VIE). Escuela de Biología, 2019 En los últimos años se ha evidenciado que el uso de células madre mesenquimales de tejido adiposo (ADSC) contribuye a la regeneración de la piel ante diferente tipo de heridas, estimulando a las células que proliferen y a que el tejido lesionado recupere su estructura normal. Debido a las complicaciones que resultan de heridas en la piel causadas por quemaduras o bien úlceras resulta necesaria la implementación de terapias alternativas que mejoren la regeneración. Por ello se buscó comprobar el potencial regenerador de las ADSC. Para esto se emplearon 5 grupos de roedores a los que se les realizó una herida cutánea y se les aplicó los siguientes tratamientos: solución salina como control negativo, ADSC en suspensión, un andamio de agarosa, un andamio de agarosa con ADSC, y finalmente un producto comercial como control positivo. Se calculó la tasa de cierre de la herida y se realizaron análisis histológicos. Aunque no hubo diferencias significativas en el tiempo de cierre de la herida entre los diferentes tratamientos, a nivel histológico si se evidenció que aquellos grupos tratados con ADSC presentaron un mejor proceso regenerativo que el resto de los tratamientos, principalmente observado en una menor inflamación, ausencia de paraqueratosis y mayor retracción de la herida, indicando así el potencial regenerativo de estas células en lesiones de piel.

The sieve elements are the only plant compartments, where phytoplasmas can survive and propagate. Therefore, this chapter is focussed on the specific molecular and cell-biological properties of the sieve element. Sieve element-companion cell complexes arise from (pro)cambial mother cells induced by key genes known to be decisive for sieve-element differentiation. The special anatomy, cell biology, and plasma-membrane outfit of sieve elements allows them to act collectively as a tube system that is able to drive a mass flow against the flow induced by transpiration. Plasmodesmal corridors are vital for the translocation of photoassimilates and systemic signals and for survival of the enucleate sieve elements. Of paramount importance is the Ca2+-dependent gating of plasmodesmata by callose and proteins. Hence, some of the complex, regulatory mechanisms to maintain Ca2+ homoeostasis in sieve elements are presented. Finally, the peculiarities of the chemical and physical sieve-element environment offered to phytoplasmas are discussed.

It has been demonstrated that protein content and concentration are higher in mononucleate tannin-cells than in the parenchyma cells of Sambucus racemosa. Cytoplasmic and nuclear free acid proteins markedly prevail here. It is believed that they may be enzymatic proteins. Increase of acid proteins content within the nucleus of tannin cells causes an increase of the nucleus size. The content of nuclear bound basic proteins in tannin cells, may be lower than in the neighbouring parenchymal cells.

We compared microsporogenesis and flower development in Eucalyptus urophylla × E. tereticornis. In this study, although microsporogenesis and cytokinesis occurred simultaneously during meiosis of pollen mother cells, we observed a strong asynchronism in different anthers from a flower bud. The developmental period of microsporogenesis in anthers originated from the long thrum before the short thrum. Flower development was also asynchronous at different locations on a branch. The flower buds grew on the lower side of the branch and showed greater increases in diameter. In addition, we observed a relationship between microsporogenesis development and flower bud diameter growth. Generally, when the pachytene stage was first observed in a small single flower bud growing on top of a flowering branch, the remaining microsporogenesis stages (from diplotene to tetrad) in the whole branch occurred over the next 5-9 days. Thus, the start of microsporogenesis in E. urophylla × E. tereticornis could be determined, which may be applicable to future breeding studies.

The length and breadth of the cambial initials and their derivatives have been examined in Polyalthia longifolia, a tropical tree possessing non-storied cambium. Taking the average size of the initials and the elements originating from them, most of the sieve-tube elements have been found to be slightly shorter in length than the fusiform initials. On the other hand, a few of these are still shorter - almost half of the fusiform initials, due to transverse or somewhat oblique divisions in the sieve element mother cells. The vessel elements are slightly shorter but 5-6 times wider than the fusiform initials. The parenchyma strands, in phloem comprising cells storing starch or tannin (pps), in xylem accumulating starch only (ssps), are more or less equal to fusiform initials indicating that the xylem and phloem mother cells forming parenchyma cells have not undergone any major change except for transverse divisions. The individual vessel-associated parenchyma cells (v.a.p. cells) are wider but much shorter in length as compared to the starch-storing parenchyma cells (s.s.p. cells) indicating that more transverse divisions have occured in the strands of the former than those of the latter. Among all the cambial derivatives, the fibers exhibit maximum increase in length, due to intrusive growth. The ray parenchyma cells are slightly longer than the ray initials possibly due to the elongation of these initials during their transformation into vascular ray cells.

The changes observed in tissues of the anther have been referred to the increasing sizes of the buds and the anthers. The enclosed table present the synchronization of several stages of development of such anther tissues as wall layers, tapetum and pollen mother cells.

To thrive in an ever-changing environment, microbes must widely distribute their progeny to colonize new territory. Simultaneously, they must evolve and adapt to the stresses of unpredictable surroundings. In both of these regards, diversity is key—if an entire population moved together or responded to the environment in the same way, it could easily go extinct. Here, we show that the epigenetic prion switch [SWI+] establishes a specialized subpopulation with a “pioneer” phenotypic program in Saccharomyces cerevisiae. Cells in the pioneer state readily disperse in water, enabling them to migrate and colonize new territory. Pioneers are also more likely to find and mate with genetically diverse partners, as inhibited mating-type switching causes mother cells to shun their own daughters. In the nonprion [swi−] state, cells instead have a “settler” phenotype, forming protective flocs and tending to remain in their current position. Settler cells are better able to withstand harsh conditions like drought and alkaline pH. We propose that these laboratory observations reveal a strategy employed in the wild to rapidly diversify and grant distinct, useful roles to cellular subpopulations that benefit the population as a whole., Author summary Microbial species do not have control over their environment. In order to survive changes (for example, in temperature, pressure, humidity, or nutrient levels), microbes must either migrate to more habitable locations or adapt to better tolerate the changing environment. Such adaptation is typically thought to come about through changes in the genetic code. Yet an alternative path also exists. In baker’s yeast, prion switching allows cells to acquire new states that may each be better adapted to different environments. Prion switching is reversible and involves no genetic change, instead relying on alternate heritable protein conformations. In this study, we show that a particular yeast prion called [SWI+] enhances the ability of cells to disperse in flowing water and also favors mating with dissimilar partners, promoting genetic diversification. Therefore, in nature, this prion could assist yeast to both migrate and adapt to new environments. Converting to this “pioneer” state comes with a trade-off: cells harboring [SWI+] are less fit in all stressful environments we tested. Thus, the prion switch serves to specialize cells either into “pioneers” that explore more physical and genetic space or into “settlers” that tend to remain where they are and are better able to survive harsh conditions.

In flowering plants, germ cells are formed via tightly coordinated patterning processes that facilitate specification of spore mother cells and meiosis during sporogenesis, as well as functional differentiation of germ cells in gametogenesis. Studies using the conventional Arabidopsis system and the newly emerged bryophyte system have revealed novel interactions between regulatory factors that restrict the number of spore mother cells, and evolutionarily conserved factors that promote germ cell differentiation. This short review summarizes recent advances in our understanding of the cellular events that lead to the formation of germ cells in plants, and highlights questions that remain to be addressed in the field.

Clonal cells can make different fate decisions, but it is often unclear to what extent these decisions are autonomous or predetermined. Here, we introduce a live-cell reporter for the pluripotency factor OCT4 into human embryonic stem cells to understand how they choose between self-renewal and differentiation. By tracing the histories of individual cells over multiple generations, we found that cells whose offspring were destined to differentiate showed decreased expression of OCT4 long before exposure to the differentiation stimulus. OCT4 levels were lineage-dependent; however, during cell division, mother cells distributed OCT4 asymmetrically to daughters. The resulting ratio of OCT4 between sister cells—established within minutes of mitosis—was predictive of downstream fates: cells receiving a greater ratio of maternal OCT4 showed sustained OCT4 levels and a reduced capacity to differentiate. Our observations imply that the choice between two developmental fates is almost entirely predetermined at the time of cell birth through inheritance of a pluripotency factor.

Antibiotic Resistance In dividing bacterial cells, asymmetric distribution of cell wall constituents occurs between mother cells and their progeny. Asymmetric distribution of efflux machinery in a growing population of bacterial cells results in heterogeneity in antibiotic resistance. One consequence is that in the presence of low levels of antibiotic, older cells tend to live longer than younger cells. Using a microfluidic device to trap and measure dividing cells, Bergmiller et al. showed that AcrAB-TolC, the main multidrug efflux pump of Escherichia coli , clusters at the pole of older cells (see the Perspective by Barrett et al. ). As cell division proceeds and daughter cells age, they too gradually accumulate polar efflux pumps. Science , this issue p. [311][1]; see also p. [247][2] [1]: /lookup/doi/10.1126/science.aaf4762 [2]: /lookup/doi/10.1126/science.aan0348

After completing their functioning, synaptonemal complexes (SCs) degrade during the diplotene stage. In the pollen mother cells of rye Secale cereale L., this occurs through the formation of gaps in lateral elements of the SCs and the shortening of fragments of SCs until their complete disappearance. However, when contrasting SCs with silver nitrate solution at a pH 3.5–4.5, these gaps appear to be filled with threads associated with SC lateral elements. As the diplotene stage proceeds and gradual degradation of SC fragments continues, these threads turn into submicroscopic spirals. In this study, we found that the threads and spirals associated with degrading synaptonemal complexes are stained by antibodies to the ASY1 protein of Arabidopsis thaliana lateral elements and thus are degradation products of the lateral elements of SCs.

In Actinidia arguta, the I tunc layer is formed by four cell complexes which descend from single initials. These initials are positioned in a corner of their complex, around the meristem axis. The meristematic activity of the I tunic layer depends on the formative divisions of the initials; the entire I tunic layer above the youngest leaf primordia is formed during the time the initials undergo only 4-8 divisions. In light of the development of the twin cell complexes. it is impossible for cells to be displaced from the I tunic layer into the meristem. The supposition is set forth that the impermanent. mericlinal sectors on variegated perinclinal chimeras develop due to periclinal cleavages within the subcomplexes which derive from tissue mother cells. Whereas. the cell initials do not undergo periclinal divisions and are not displaced.

In 1964, two new types of apogamy were described in ferns. The sporangia contain at the starting-point 16 spore mother cells and at the endingpoint 32 diplospores. On the one hand, the meiosis is replaced by a mitosis, on the other hand, the first meiotic division aborts and the restituition nucleus divides mitotically. The author's observations imply that the second process is a variant of the first one.

In vitro studies of the ontogeny of stomata of young leaves of Tradescantia virginiana L. showed that: 1) translocation of nuclei, often along long, winding paths took place in companion cell mother cells before the onset of asymmetric mitosis, 2) the reorientation of the entire mitotic apparatus took place during division of quard cell mother cells. Pertinent factors which may play a role in both processes are indicated.

Two new partial amphiploids SN20 and SN122, derived from crosses between Elytrigia elongata and common wheat Yannong15 and Shannongfu63, were found resistant to powdery mildew, a serious fungal wheat disease. Cytogenetic observations showed that each SN20 and SN122 plant had 56 chromosomes. The chromosomes in most pollen mother cells formed approximately 28 bivalents, thereby showing a high degree of cytogenetic stability. Genomic in situ hybridization using St-genomic DNA from Pseudoroegneria strigosa as a probe and ABD-genomic DNA from Chinese Spring wheat as a blocker demonstrated that the genomic formulas for the alien chromosomes in SN20 and SN122 were 2 St + 10 JS + 2 J and 2 St + 8 JS + 4 J, respectively. These wheat E. elongata partial amphiploids represent a potential novel source of resistance to powdery mildew for wheat breeding.

Meiosis is a highly specialized cell division that facilitates the production of haploid gametes from diploid mother cells. It is characterized by unique chromatin structures and chromatin associated protein complexes. The analysis of these structures and complexes has greatly benefited from and relied on the visualization of meiotic proteins in diverse preparations of meiocytes. In this chapter we summarize methods that can be used for the characterization of the behavior and localization of meiotic proteins in mammalian meiocytes.

Asymmetric cell divisions establish the patterning of stomata in maize. PAN receptor-like kinases were thought to start a signalling cascade leading to pre-mitotic polarization of the cell. Re-analysis of mutants now reveals that the SCAR/WAVE complex is involved in the early initiation of polarity in mother cells.

The present study was carried out to determine crossability between Brassica napus and B. rapa, to elucidate chromosome homoeology between different Brassica genomes in the F1 hybrids and to estimate genetic variability in F2 progenies of the crosses. Crosses between B. napus (AACC, 2n = 38) and B. rapa (AA, 2n = 20) vars. brown sarson, yellow sarson and toria were attempted and the hybrid derivatives were advanced to F2 generation. Hybrid recoveries were higher when B. napus was used as a female parent. The F1 plants were luxuriant in growth and intermediate to their progenitor parents for morphological attributes. The meiotic studies of F1 plants (AAC, 2n = 29) showed 10 bivalents in the majority of pollen mother cells analyzed. A maximum of 12 II was found in a few cells. The occurrence of multivalent associations as trivalent and quadrivalent at metaphase I, and a bridge-fragment configuration at anaphases were attributed to homoeology between A and C genomes. In the F2 generation, a high percentage o...

Cytogenetic studies are a useful tool for the study of systematics and evolution in plants. The current paper reports on polyad production during microsporogenesis of Hippocratea volubilis. The analyzed material was collected in the Ecological Station of Caiua in Diamante do Norte, PR, Brazil. The meiotic analysis was performed using a squashing technique and the stain was 1% acetic carmine. The chromosome segregation process during meiotic division was normal. However, pollen mother cells (PMCs) were bonded in fours or twos, through cytoplasmic channels during the whole microsporogenesis. After telophase II, four-PMC complexes produced tetra-tetrads with 16 microspores, whereas two-PMC complexes produced bi-tetrads with eight microspores. Microspores formed in the process remained bonded and formed polyads with 16 or eight pollen grains.

In the leaves of rice (Oryza sativa), stomatal initials arose from two asymmetric cell divisions and a symmetric division. Guard mother cells (GMCs) and long cells in stomatal files (LCSs) were formed through the first asymmetric division of the precursor cell of GMCs. Subsidiary cells (SCs) were produced by the second asymmetric division of subsidiary mother cells or LCSs. Following SC formation, GMCs divided once symmetrically to generate guard cells and then differentiated terminally to form mature stomata. The developmental patterns of long cells, prickle hairs and short cells (phellem cells and silica cells) were also examined. Interestingly, we found that the different developmental stages of stomata and epidermal cells occurred in the similar location of immature leaves of the same phyllotaxis. In addition, two spacing patterns ("one stoma, one long cell" and "one short cell row") probably exist in rice leaves.

Platycodon grandiflorus is an important medicinal plant in China and its root has been used as medicine or food for centuries. Polyploids are usually valuable because they exhibit increased biomass and contain effective medicinal compounds. Polyploidy induction was successfully achieved in this plant in a previous study by apical shoot tip treatment of young seedlings for 72 h using semi-solid 0.05% colchicine. Polyploidy was further confirmed by meiosis behavior of pollen mother cells in this study. The meiosis of diploid controls is regular, with normal chromosome pairing, and diploids were identified with 2n = 2x = 18 chromosomes at metaphaseI, nine bivalents at diakinesis and 9–9 separation at meiosis I, then differentiating into tetrads that subsequently give rise to mature pollen grains. Induced tetraploids were cytogenetically distinguished from diploids by the occurrence of 36 chromosomes at diakinesis with different combinations of univalents, bivalents, trivalents, quadrivalents, and multivalent...

While studying meiosis in the male tract of Valeriana wallichii DC (Valerianaceae). polymorphism in size as well as chromosome number was observed in its pollen mother cells. The present report is based on study undertaken in ten populations of the species; 8 from J&K (India) and 2 from Uttrakhand (India). In all the anthers studied from plants of these populations, pollen mother cells could be differentiated as small (20–30 μm), medium (30–50 μm) and large sized (50–65 μm). In two populations (Noorichamb, J&K and Chakrata, UK), besides size, PMCs with different ploidy level were also observed. While the small and medium PMCs had normal chromosome number with 16 bivalents, some of the large PMCs were tetraploid having 64 chromosomes. Rarely, some pmcs at early prophase- I were also seen in a seemingly fusing state in some of the anthers. Size difference in PMCs also got reflected in the size of pollen grains and these could be classified as small (

The paper presents previously undescribed abnormalities of phragmoplast formation in pollen mother cells of grass haploids and allohaploids (wide hybrids of the first generation). These abnormal phenotypes reveal and illustrate occasional unknown stages of phragmoplast formation in dividing plant cells and indicate the special regulation of their initiation, as well as confirm data on this process obtained by other approaches.