Control of flowering in bougainvillea "san diego red.": metabolism of benzyladenine and the action of gibberellic Acid in relation to short day induction

Benzyladenine (BA) and short day (SD) induction promote and gibberellic acid (GA) inhibits flowering in Bougainvillea “San Diego Red.” GA is an overriding vegetative signal maintaining plants in a vegetative state even when BA is applied in SD conditions. SD promotes a more rapid conversion of BA to the ribotide and other “polar derivatives” (containing adenine derivatives). This effect of SD on BA metabolism is seen in root, stem, and apical bud tissues and is completely prevented by prior or simultaneous application of GA. GA treatment reduces the rate of polar derivative formation to that found in plants held in long days. The working hypothesis is that SD promotes flowering in Bougainvillea owing to reduced transport of gibberellins from leaves to roots and apical buds permitting metabolism of cytokinin, and perhaps other purine bases, to more polar forms that are more readily translocated and active in promoting reproductive development of the inflorescences axes.     

Detection of Destruxins in Silkworm Larvae Infected with Metarrhizium anisopliae

Ultrastructure of the cortical cells of living bark, leaf buds, and flower buds of apple trees (Malus pumila Mill. var. domestica Schneid, cv. McIntosh) was studied. The ultrastructural changes in preexisting plastids, leading to formation of the plastid initials and subsequent intermediates in the formation of plastids, started in mid-January or early February and continued to occur through late March. The plastid initials of apple trees resemble that of poplar, and prolamellar bodies were abundant in the developing intermediates in the cells of leaf buds and flower buds. Association of the endoplasmic reticulum and vesicles with developing plastid initials suggests that the former two organelles may possibly participate in the development of the plastid initial. Thus, formation of plastids from plastid initials takes place seasonally at this stage.     

Studies on cytokinin-controlled bud formation in moss protonemata

Application of cytokinins to moss protonemata of the proper physiological age causes bud formation on specific cells (caulonema). During the early stages of their development, buds revert to protonemal filaments if the cytokinin has been removed by washing the protonemata. This indicates that the hormone is not acting as a “trigger” but has to be present during a critical period of time until differentiation is stabilized. Autoradiographs of protonemata treated with a labeled cytokinin, benzyladenine-benzyl-7-¹⁴C, show a striking accumulation of the radioactivity in caulonema cells which are in the stage of bud formation, and in the buds themselves. Cells which did not react to the hormone contained very little radioactivity. The accumulation of benzyladenine in the “target cells” may be due to the presence of binding sites which, in turn, may distinguish responding cells from non-responding ones.     

Endogenous abscisic Acid in relation to bud growth in alternate bearing ;valencia' orange

An investigation was conducted into the relation of ABA (cis-trans-abscisic acid) in the dormant buds of alternate bearing `Valencia' orange (Citrus sinensis [L.] Osbeck) trees. ABA did not appear to be related to alternate bearing but t-ABA (2-transabscisic acid) did. There was 5- to 10-fold more t-ABA than ABA in the buds. There was more t-ABA in the buds of the “on” trees than in the buds of the “off” trees, and a drastic drop in t-ABA in both types of buds as spring growth approached. Bud dormancy and readiness for growth as related to t-ABA are discussed.     

E‐cadherin mediates apical membrane initiation site localisation during de novo polarisation of epithelial cavities

Individual cells within de novo polarising tubes and cavities must integrate their forming apical domains into a centralised apical membrane initiation site (AMIS). This is necessary to enable organised lumen formation within multi‐cellular tissue. Despite the well‐documented importance of cell division in localising the AMIS, we have found a division‐independent mechanism of AMIS localisation that relies instead on Cadherin‐mediated cell–cell adhesion. Our study of de novo polarising mouse embryonic stem cells (mESCs) cultured in 3D suggests that cell–cell adhesion localises apical proteins such as PAR‐6 to a centralised AMIS. Unexpectedly, we also found that mESC clusters lacking functional E‐cadherin still formed a lumen‐like cavity in the absence of AMIS localisation but did so at a later stage of development via a “closure” mechanism, instead of via hollowing. This work suggests that there are two, interrelated mechanisms of apical polarity localisation: cell adhesion and cell division. Alignment of these mechanisms in space allows for redundancy in the system and ensures the development of a coherent epithelial structure within a growing organ.     

The Control of Growth Habit of Marquillo x Kenya Farmer Wheat Dwarf I by Temperature

The Marquillo × Kenya Farmer 1 “grass-clump” dwarf selection of Triticum aestivum L. was grown under continuous 2000 foot candle light and several regimes of alternating 16° and 26° temperatures combined in total cycle lengths of 6, 12, 24, or 48 hr. Plants at 26° grew as normal wheat. Those exposed to 0.25 to 2 hr of 16° per cycle showed typical “grass-clump” dwarf characteristics which were independent of the cycle length. Treatments with 16° exposures of 4 to 8 hr per 24 hr and 12 to 16 hr per 48 hr exhibited vegetative “grass-clump” dwarfness for 40 days but later displayed extensive reproductive development. Longer 16° treatments killed the plants at a very early stage of vegetative development before floral initiation. The data supported an hypothesis that all 4 growth habits were related to the temperature sensitivity of the vegetative meristem. The cessation of meristem development was possibly due to the accumulation of a stable inhibitory substance produced at low temperatures.     

Genetic regulation of plant shoot stem cells

This article describes the main features of plant stem cells and summarizes the results of studies of the genetic control of stem cell maintenance in the apical meristem of the shoot. It is demonstrated that the WUS-CLV gene system plays a key role in the maintenance of shoot apical stem cells and the formation of adventitious buds and somatic embryos. Unconventional concepts of plant stem cells are considered.     

Lipid Accumulation during the Establishment of Kleptoplasty in Elysia chlorotica

The establishment of kleptoplasty (retention of “stolen plastids”) in the digestive tissue of the sacoglossan Elysia chlorotica Gould was investigated using transmission electron microscopy. Cellular processes occurring during the initial exposure to plastids were observed in laboratory raised animals ranging from 1–14 days post metamorphosis (dpm). These observations revealed an abundance of lipid droplets (LDs) correlating to plastid abundance. Starvation of animals resulted in LD and plastid decay in animals <5 dpm that had not yet achieved permanent kleptoplasty. Animals allowed to feed on algal prey (Vaucheria litorea C. Agardh) for 7 d or greater retained stable plastids resistant to cellular breakdown. Lipid analysis of algal and animal samples supports that these accumulating LDs may be of plastid origin, as the often algal-derived 20∶5 eicosapentaenoic acid was found in high abundance in the animal tissue. Subsequent culturing of animals in dark conditions revealed a reduced ability to establish permanent kleptoplasty in the absence of photosynthetic processes, coupled with increased mortality. Together, these data support an important role of photosynthetic lipid production in establishing and stabilizing this unique animal kleptoplasty.     

Cryo-scanning electron microscopic study on freezing behaviors of tissue cells in dormant buds of larch (Larix kaempferi)

The freezing behavior of dormant buds in larch, especially at the cellular level, was examined by a Cryo-SEM. The dormant buds exhibited typical extraorgan freezing. Extracellular ice crystals accumulated only in basal areas of scales and beneath crown tissues, areas in which only these living cells had thick walls unlike other tissue cells. By slow cooling (5 °C/day) of dormant buds to −50 °C, all living cells in bud tissues exhibited distinct shrinkage without intracellular ice formation detectable by Cryo-SEM. However, the recrystallization experiment of these slowly cooled tissue cells, which was done by further freezing of slowly cooled buds with LN and then rewarming to −20 °C, confirmed that some of the cells in the leaf primordia, shoot primordia and apical meristem, areas in which cells had thin walls and in which no extracellular ice accumulated, lost freezable water with slow cooling to −30 °C, indicating ability of these cells to adapt by extracellular freezing, whereas other cells in these tissues retained freezable water with slow cooling even to −50 °C, indicating adaptation of these cells by deep supercooling. On the other hand, all cells in crown tissues and in basal areas of scales, areas in which cells had thick walls and in which large masses of ice accumulated, had the ability to adapt by extracellular freezing. It is thought that the presence of two types of cells exhibiting different freezing adaptation abilities within a bud tissue is quite unique and may reflect sophisticated freezing adaptation mechanisms in dormant buds.     

Herbivores Influence the Growth,Reproduction, and Morphology of a Widespread Arctic Willow

Shrubs have expanded in Arctic ecosystems over the past century, resulting in significant changes to albedo, ecosystem function, and plant community composition. Willow and rock ptarmigan (Lagopus lagopus, L. muta) and moose (Alces alces) extensively browse Arctic shrubs, and may influence their architecture, growth, and reproduction. Furthermore, these herbivores may alter forage plants in such a way as to increase the quantity and accessibility of their own food source. We estimated the effect of winter browsing by ptarmigan and moose on an abundant, early-successional willow (Salix alaxensis) in northern Alaska by comparing browsed to unbrowsed branches. Ptarmigan browsed 82–89% of willows and removed 30–39% of buds, depending on study area and year. Moose browsed 17–44% of willows and browsed 39–55% of shoots. Browsing inhibited apical dominance and activated axillary and adventitious buds to produce new vegetative shoots. Ptarmigan- and moose-browsed willow branches produced twice the volume of shoot growth but significantly fewer catkins the following summer compared with unbrowsed willow branches. Shoots on browsed willows were larger and produced 40–60% more buds compared to unbrowsed shoots. This process of shoot production at basal parts of the branch is the mechanism by which willows develop a highly complex “broomed” architecture after several years of browsing. Broomed willows were shorter and more likely to be re-browsed by ptarmigan, but not moose. Ptarmigan likely benefit from the greater quantity and accessibility of buds on previously browsed willows and may increase the carrying capacity of their own habitat. Despite the observed tolerance of willows to browsing, their vertical growth and reproduction were strongly inhibited by moose and ptarmigan. Browsing by these herbivores therefore needs to be considered in future models of shrub expansion in the Arctic.     

Prey Capture and Phagocytosis in the Choanoflagellate Salpingoeca rosetta

Choanoflagellates are unicellular and colonial aquatic microeukaryotes that capture bacteria using an apical flagellum surrounded by a feeding collar composed of actin-filled microvilli. Flow produced by the apical flagellum drives prey bacteria to the feeding collar for phagocytosis. We report here on the cell biology of prey capture in rosette-shaped colonies and unicellular “thecate” or substrate attached cells from the choanoflagellate S. rosetta. In thecate cells and rosette colonies, phagocytosis initially involves fusion of multiple microvilli, followed by remodeling of the collar membrane to engulf the prey, and transport of engulfed bacteria into the cell. Although both thecate cells and rosette colony cells produce ∼70 nm “collar links” that connect and potentially stabilize adjacent microvilli, only thecate cells were observed to produce a lamellipod-like “collar skirt” that encircles the base of the collar. This study offers insight into the process of prey ingestion by S. rosetta, and provides a context within which to consider potential ecological differences between solitary cells and colonies in choanoflagellates.     

Development of maize plants from cultured shoot apices

Excised shoot apices of maize (Zea mays L.), comprising the apical meristem and one or two leaf primordia, have been cultured and can form rooted plantlets. The plantlets, derived from meristems that had previously formed 7–10 nodes, develop into mature, morphologically normal plants with as many nodes as seed-grown plants. These culture-derived plants exhibited the normal pattern of development, with regard to the progression of leaf lengths along the plant and position of axillary buds and aar shoots. Isolation of the meristem from previously formed nodes reinitiates the pattern and number of nodes formed in the new plant. Thus, cells of the meristem of a maize plant at the seedling stage are not determined to form a limited number of nodes.     

Cadmium Induced Ultrastructural Changes in Shoot Apical Meristem of Elodea Canadensis Rich.

The ultrastructure of cells of ground meristem in the peripheral zone of shoot apical meristem in Elodea canadensis Rich. was studied after treatment with cadmium in concentrations 0.5, 1, 2, 3, 5, and 6 g(Cd²⁺) m⁻³. After 5 d treatment, changes in the structural organisation of the plastid apparatus were found, namely in proplastid, amyloplast, and amoeboid stages of plastid development. This revised version was published online in June 2006 with corrections to the Cover Date.     

A novel DNA polymerase homologous to Escherichia coli DNA polymerase I from a higher plant, rice (Oryza sativa L.)

A novel DNA polymerase, designated as OsPolI-like, has been identified from the higher plant, rice (Oryza sativa L. cv. Nipponbare). The OsPolI-like cDNA was 3765 bp in length, and the open reading frame encoded a predicted product of 977 amino acid residues with a molecular weight of 100 kDa. The OsPolI-like gene has been mapped to chromosome 8 and contains 12 exons and 11 introns. The encoded protein showed a high degree of sequence and structural homology to Escherichia coli pol I protein, but differed from DNA polymerase γ and θ. The DNA polymerase domain of OsPolI-like showed DNA polymerase activity. Subcellular fractionation analysis suggested that the protein is localized in the plastid. Northern and western blotting, and in situ hybridization analyses demonstrated preferential expression of OsPolI-like in meristematic tissues such as shoot apical meristem, root apical meristem, leaf primordia and the marginal meristem. Interestingly, no expression was detected in mature leaves, although they have a high chloroplast content. These properties indicated that OsPolI-like is a novel plant DNA polymerase. The function of OsPolI-like is discussed in relation to plastid maturation.     

Endogenous Short Period Rhythms in the Movements of Unifoliate Leaves of Phaseolus angularis Wight

Rhythmic rotational movements with the midvein as the axis have been observed in the unifoliate leaves of Phaseolus angularis Wight grown under controlled environmental conditions with continuous light. The mean period of this movement for all leaves was 53.2 ± 4.3 minutes and remained constant as the leaf matured, except after removal of the apical meristem and emerging trifoliate leaf when the period increased by about 5 minutes. The amplitude of the movement also remained constant as the leaf matured. These rotational movements were pronounced when the leaf blade was in a horizontal position and were not evident during the downward or “sleep” movements of the leaf. This movement began 3 days after leaf unfolding and continued for at least 6 days. It was most pronounced at the time of inflection of the leaf length growth curve after the logarithmic phase of growth.     

Early events of multiple bud formation and shoot development in soybean embryonic axes treated with the cytokinin, 6-benzylaminopurine

Early events of multiple bud formation and shoot development in germinating soybean embryonic axes treated for 24 hr with the cytokinin, 6-benzylaminopurine (BAP), were compared to the development of untreated control axes using four different techniques: photomicrography, scanning electron microscopy, histology, and autoradiography. Shoot apex development in BAP-treated embryonic axes was delayed by about 9 to 15 hr. A transient inhibition of DNA synthesis in the primary apical meristem and axillary buds was observed with subsequent changes in the timing of cell division patterns in these regions. Meristematic regions (supernumerary vegetative buds) were observed in BAP-treated axes around the perimeter of the apical dome at and above the level of the axillary buds. Cells elongated from some of the BAP-induced meristematic regions to form four to six shoots. In the absence of BAP, excision of the primary apical meristem and/or axillary buds did not result in multiple bud formation. These results suggest that transient exposure to BAP interrupted chromosomal DNA replication and reprogrammed the developmental fate of a large number of cells in the shoot apex. We postulate that interruption of DNA synthesis, either directly, by interfering with DNA replication, or indirectly, by preventing entry into S-phase, effected redetermination of the shoot apex cells.     

Superparamagnetic Iron Oxide Nanoparticles Labeling of Bone Marrow Stromal (Mesenchymal) Cells Does Not Affect Their “Stemness”

Superparamagnetic iron oxide nanoparticles (SPION) are increasingly used to label human bone marrow stromal cells (BMSCs, also called “mesenchymal stem cells”) to monitor their fate by in vivo MRI, and by histology after Prussian blue (PB) staining. SPION-labeling appears to be safe as assessed by in vitro differentiation of BMSCs, however, we chose to resolve the question of the effect of labeling on maintaining the “stemness” of cells within the BMSC population in vivo. Assays performed include colony forming efficiency, CD146 expression, gene expression profiling, and the “gold standard” of evaluating bone and myelosupportive stroma formation in vivo in immuncompromised recipients. SPION-labeling did not alter these assays. Comparable abundant bone with adjoining host hematopoietic cells were seen in cohorts of mice that were implanted with SPION-labeled or unlabeled BMSCs. PB+ adipocytes were noted, demonstrating their donor origin, as well as PB+ pericytes, indicative of self-renewal of the stem cell in the BMSC population. This study confirms that SPION labeling does not alter the differentiation potential of the subset of stem cells within BMSCs.     

Characterization of the Denitrification-Associated Phosphorus Uptake Properties of “Candidatus Accumulibacter phosphatis” Clades in Sludge Subjected to Enhanced Biological Phosphorus Removal

To characterize the denitrifying phosphorus (P) uptake properties of “Candidatus Accumulibacter phosphatis,” a sequencing batch reactor (SBR) was operated with acetate. The SBR operation was gradually acclimated from anaerobic-oxic (AO) to anaerobic-anoxic-oxic (A2O) conditions by stepwise increases of nitrate concentration and the anoxic time. The communities of “Ca. Accumulibacter” and associated bacteria at the initial (AO) and final (A2O) stages were compared using 16S rRNA and polyphosphate kinase genes and using fluorescence in situ hybridization (FISH). The acclimation process led to a clear shift in the relative abundances of recognized “Ca. Accumulibacter” subpopulations from clades IIA > IA > IIF to clades IIC > IA > IIF, as well as to increases in the abundance of other associated bacteria (Dechloromonas [from 1.2% to 19.2%] and “Candidatus Competibacter phosphatis” [from 16.4% to 20.0%]), while the overall “Ca. Accumulibacter” abundance decreased (from 55.1% to 29.2%). A series of batch experiments combined with FISH/microautoradiography (MAR) analyses was performed to characterize the denitrifying P uptake properties of the “Ca. Accumulibacter” clades. In FISH/MAR experiments using slightly diluted sludge (∼0.5 g/liter), all “Ca. Accumulibacter” clades successfully took up phosphorus in the presence of nitrate. However, the “Ca. Accumulibacter” clades showed no P uptake in the presence of nitrate when the sludge was highly diluted (∼0.005 g/liter); under these conditions, reduction of nitrate to nitrite did not occur, whereas P uptake by “Ca. Accumulibacter” clades occurred when nitrite was added. These results suggest that the “Ca. Accumulibacter” cells lack nitrate reduction capabilities and that P uptake by “Ca. Accumulibacter” is dependent upon nitrite generated by associated nitrate-reducing bacteria such as Dechloromonas and “Ca. Competibacter.”     

Fibroblast Growth Factor Receptors-1 and -3 Play Distinct Roles in the Regulation of Bladder Cancer Growth and Metastasis: Implications for Therapeutic Targeting

Fibroblast growth factor receptors (FGFRs) are activated by mutation and overexpressed in bladder cancers (BCs), and FGFR inhibitors are currently being evaluated in clinical trials in BC patients. However, BC cells display marked heterogeneity in their responses to FGFR inhibitors, and the biological mechanisms underlying this heterogeneity are not well defined. Here we used a novel inhibitor of FGFRs 1–3 and RNAi to determine the effects of inhibiting FGFR1 or FGFR3 in a panel of human BC cell lines. We observed that FGFR1 was expressed in BC cells that also expressed the “mesenchymal” markers ZEB1 and vimentin, whereas FGFR3 expression was restricted to the E-cadherin- and p63-positive “epithelial” subset. Sensitivity to the growth-inhibitory effects of BGJ-398 was also restricted to the “epithelial” BC cells and it correlated directly with FGFR3 mRNA levels but not with the presence of activating FGFR3 mutations. In contrast, BGJ-398 did not strongly inhibit proliferation but did block invasion in the “mesenchymal” BC cells in vitro. Similarly, BGJ-398 did not inhibit primary tumor growth but blocked the production of circulating tumor cells (CTCs) and the formation of lymph node and distant metastases in mice bearing orthotopically implanted “mesenchymal” UM-UC3 cells. Together, our data demonstrate that FGFR1 and FGFR3 have largely non-overlapping roles in regulating invasion/metastasis and proliferation in distinct “mesenchymal” and “epithelial” subsets of human BC cells. The results suggest that the tumor EMT phenotype will be an important determinant of the biological effects of FGFR inhibitors in patients.