Furrow Placement Research Articles

A kinesin-13 family kinesin in Trypanosoma brucei regulates cytokinesis and cytoskeleton morphogenesis by promoting microtubule bundling.

The early branching eukaryote Trypanosoma brucei divides uni-directionally along the longitudinal cell axis from the cell anterior toward the cell posterior, and the cleavage furrow ingresses along the cell division plane between the new and the old flagella of a dividing bi-flagellated cell. Regulation of cytokinesis in T. brucei involves actomyosin-independent machineries and trypanosome-specific signaling pathways, but the molecular mechanisms underlying cell division plane positioning remain poorly understood. Here we report a kinesin-13 family protein, KIN13-5, that functions downstream of FPRC in the cytokinesis regulatory pathway and determines cell division plane placement. KIN13-5 localizes to multiple cytoskeletal structures, interacts with FPRC, and depends on FPRC for localization to the site of cytokinesis initiation. Knockdown of KIN13-5 causes loss of microtubule bundling at both ends of the cell division plane, leading to mis-placement of the cleavage furrow and unequal cytokinesis, and at the posterior cell tip, causing the formation of a blunt posterior. In vitro biochemical assays demonstrate that KIN13-5 bundles microtubules, providing mechanistic insights into the role of KIN13-5 in cytokinesis and posterior morphogenesis. Altogether, KIN13-5 promotes microtubule bundle formation to ensure cleavage furrow placement and to maintain posterior cytoskeleton morphology in T. brucei.

Increase the Efficient Use of Phosphorus Fertilizer for Maize in the Calcareous Soils

ABSTRACT Phosphorus (P) is one of the 17 essential plant nutrients, and it is critical for plant metabolism, photosynthesis, and growth. P fertilizers are also critical for crop production and global food security. Type and application method of P fertilizer may lead to increased P accumulation and crop production in the Ganges delta soils. The aim of the present study is to increase the P use efficiency (PUE) by two different P application methods for maize cultivation. The experiment comprised a factorial combination of two methods (broadcasting and furrow placement) and three rates of P fertilizer (36, 48, and 60 kg P/ha). Considering P application methods, furrow placement gave 8.66–27.92% yield benefit over broadcasting method. Maize yield, PUE by crop plant, partial factor productivity, economic efficiency, and P concentration in leaf were remarkably higher in furrow placement than conventional broadcasting method of P application. The furrow placement exhibited higher yield at lower rate of P application (36 and 48 kg P/ha), while no significant changes were observed for grain yield between two methods for high P rate (60 kg/ha). Thus, it is concluded that furrow placement of P application at 36 and 48 kg/ha would give the best grain yield of maize in the Ganges delta floodplain soils.

Increasing the use efficiency of fertilizer phosphorus for maize in low-P Ganges Delta soils

The availability and use efficiency of phosphorus (P) is low in the acidic Ganges delta floodplain soils. The aim of the present study was to increase the use efficiency of P by varying the methods and forms of P application. The experiment comprised a factorial combination of two methods (broadcasting and furrow placement) and two forms (granular and powder) with three rates of P fertilizer application (36, 48 and 60 kg P ha−1). Results showed that furrow placement of P application gave 10%–20% yield benefit over broadcasting method. Agronomic P use efficiency, partial factor productivity, economic efficiency and leaf P concentration were remarkably higher in furrow placement of P fertilizer than conventional broadcasting method. Numerically the application of powder form P fertilizer demonstrated higher yield compared to granular form of P application. The furrow placement of P fertilizer exhibited the higher yield at lower rate of P application (36–48 kg P ha−1) while opposite trends were observed for broadcasting. Thus, it is concluded that furrow placement of P fertilizer application at 36–48 kg ha−1would give the best grain yield of maize in the Ganges delta floodplain soils.

Peripheral astral microtubules ensure asymmetric furrow positioning in neural stem cells.

Neuroblast division is characterized by asymmetric positioning of the cleavage furrow, resulting in a large difference in size between the future daughter cells. In animal cells, furrow placement and assembly are governed by centralspindlin that accumulates at the equatorial cell cortex of the future cleavage site and at the spindle midzone. In neuroblasts, these two centralspindlin populations are spatially and temporally separated. A leading pool is located at the basal cleavage site and a second pool accumulates at the midzone before traveling to the cleavage site. The cortical centralspindlin population requires peripheral astral microtubules and the chromosome passenger complex for efficient recruitment. Loss of this pool does not prevent cytokinesis but enhances centralspindlin signaling at the midzone, leading to equatorial furrow repositioning and decreased size asymmetry. These data show that basal furrow positioning in neuroblasts results from a competition between different centralspindlin pools in which the cortical pool is dominant.

Spatio-temporally separated cortical flows and spindle geometry establish physical asymmetry in fly neural stem cells

Asymmetric cell division, creating sibling cells with distinct developmental potentials, can be manifested in sibling cell size asymmetry. This form of physical asymmetry occurs in several metazoan cells, but the underlying mechanisms and function are incompletely understood. Here we use Drosophila neural stem cells to elucidate the mechanisms involved in physical asymmetry establishment. We show that Myosin relocalizes to the cleavage furrow via two distinct cortical Myosin flows: at anaphase onset, a polarity induced, basally directed Myosin flow clears Myosin from the apical cortex. Subsequently, mitotic spindle cues establish a Myosin gradient at the lateral neuroblast cortex, necessary to trigger an apically directed flow, removing Actomyosin from the basal cortex. On the basis of the data presented here, we propose that spatiotemporally controlled Myosin flows in conjunction with spindle positioning and spindle asymmetry are key determinants for correct cleavage furrow placement and cortical expansion, thereby establishing physical asymmetry.

Profiling of the Mammalian Mitotic Spindle Proteome Reveals an ER Protein, OSTD-1, as Being Necessary for Cell Division and ER Morphology

Cell division is important for many cellular processes including cell growth, reproduction, wound healing and stem cell renewal. Failures in cell division can often lead to tumors and birth defects. To identify factors necessary for this process, we implemented a comparative profiling strategy of the published mitotic spindle proteome from our laboratory. Of the candidate mammalian proteins, we determined that 77% had orthologs in Caenorhabditis elegans and 18% were associated with human disease. Of the C. elegans candidates (n=146), we determined that 34 genes functioned in embryonic development and 56% of these were predicted to be membrane trafficking proteins. A secondary, visual screen to detect distinct defects in cell division revealed 21 genes that were necessary for cytokinesis. One of these candidates, OSTD-1, an ER resident protein, was further characterized due to the aberrant cleavage furrow placement and failures in division. We determined that OSTD-1 plays a role in maintaining the dynamic morphology of the ER during the cell cycle. In addition, 65% of all ostd-1 RNAi-treated embryos failed to correctly position cleavage furrows, suggesting that proper ER morphology plays a necessary function during animal cell division.

Cytokinesis inDrosophila melanogaster

Cytokinesis is the process that physically separates two sibling cells, ensuring the proper partitioning of the nuclear and cytoplasmic contents at the end of cell division. Cytokinesis requires a fine-tuned molecular machinery that has to be assembled with high spatiotemporal precision. Drosophila melanogaster is an ideal model system to investigate this cellular process. Genetic screens performed in spermatocytes, neuroblasts, and Schneider cells revealed numerous evolutionary conserved components. These genetically amenable systems have proven to be very useful to further elucidate the cellular and molecular mechanism of cytokinesis, significantly contributing to our current understanding of this important cellular process. As in other organisms, cytokinesis is largely dependent on the mitotic spindle, providing positional cues for cleavage furrow placement and progression. However, spindle-independent mechanisms could also be important during special cases of cytokinesis, such as asymmetric cell division. Thus, powerful fly genetics combined with single-cell analysis, live imaging, and biochemical assays will continue to provide important insights into the mechanism of cytokinesis.

The Trypanosoma brucei AIR9‐like protein is cytoskeleton‐associated and is required for nucleus positioning and accurate cleavage furrow placement

SummaryAIR9 is a cytoskeleton-associated protein in Arabidopsis thaliana with roles in cytokinesis and cross wall maturation, and reported homologues in land plants and excavate protists, including trypanosomatids. We show that the Trypanosoma brucei AIR9-like protein, TbAIR9, is also cytoskeleton-associated and colocalizes with the subpellicular microtubules. We find it to be expressed in all life cycle stages and show that it is essential for normal proliferation of trypanosomes in vitro. Depletion of TbAIR9 from procyclic trypanosomes resulted in increased cell length due to increased microtubule extension at the cell posterior. Additionally, the nucleus was re-positioned to a location posterior to the kinetoplast, leading to defects in cytokinesis and the generation of aberrant progeny. In contrast, in bloodstream trypanosomes, depletion of TbAIR9 had little effect on nucleus positioning, but resulted in aberrant cleavage furrow placement and the generation of non-equivalent daughter cells following cytokinesis. Our data provide insight into the control of nucleus positioning in this important pathogen and emphasize differences in the cytoskeleton and cell cycle control between two life cycle stages of the T. brucei parasite.

Using geomorphology to assess contour furrowing in western New South Wales, Australia

This study examines landscape rehabilitation treatments installed 20–40 years ago in the Western Catchment of NSW. Treatment outcomes were assessed using geomorphic criteria, because geomorphic processes are fundamental to ecological permanence. Contour furrowing creates artificial runoff-runon sets which intercept runoff (resistance to flow by windrows microrelief and surface roughness) and promote infiltration (artificial permeability by ripping). As originally conceived, after windrows subside, flow resistance would be afforded by surface roughness under belts of vegetation. This study shows that rehabilitation treatments have a more complex relationship with the landscape than this would suggest, and that the final effect of the treatment depends on the geomorphic processes natural to the site. Treatment design should therefore be site-specific. The relevant aspects of treatment design are site location, runoff : runon ratio (expressed as furrow spacing and furrow length), furrow placement, and post-treatment management. Some long-term successes are documented. In ironstone ridge country affected by impermeable hard-setting soils, furrowing creates artificial permeability, allowing plant germination; plant material in the soil reverses hard-setting and establishes self-sustaining permeability. In stony gilgai country furrowing through vegetated patches can aid in re-establishing vegetation, but furrowing through stony runoff patches only diminishes, rather than improves, landscape function. Other landscape types will have different key attributes. In all cases, selection of appropriate sites for rehabilitation treatment is of primary importance. The 1990s NSW Soil Conservation Service best-practice included a specialised furrower, surveying techniques for accurate furrow placement along the contour, staggered gaps along each furrow line to reduce risks of gullying by windrow breakthrough, and post-treatment management of total grazing pressure. New guidelines for treatment design developed from this study include determining for each site the optimum runoff:runon ratio (which varies according to climate, gradient, vegetation, and regolith), and matching furrow spacing and furrow/gap length to local runoff:runon ratios. In stony gilgai country, furrow placement should be along the contour but within non-stony patches; elsewhere, placement should be rigorously along the contour. In ironstone ridge country, a greater runoff:runon ratio, commensurate with the area’s apparently larger patch scale, can be achieved by having more gap than furrow along each furrow line. No single rehabilitation technique will fit all landscape types, and these guidelines will ideally be developed further with investigation of other landscapes.

The effect of drip line placement on yield and quality of drip-irrigated processing tomatoes

Subsurface drip irrigation of processing tomatoes is increasing in California. The common design approach is to bury drip lines 0.2–0.36 m deep in the middle of the plant row, which places drip lines directly beneath plant rows. This design limits the use of the drip irrigation system to only those crops compatible with this drip line and bed spacing, and thus, other design approaches are being investigated to increase the flexibility of the drip systems. These approaches are installing drip lines in alternate furrows and installing drip lines in every furrow, both of which place drip lines midway between plant rows. The furrows are the result of the cultural practices used to form beds for planting.This study investigated the effect of the different drip line placements on crop yield and quality. Results showed that the highest yields occurred for the buried placement and the smallest yields for the alternate furrow placement. For the buried placement, soil water content and root density were concentrated around the drip lines, directly beneath the plant rows, while for the furrow placements, zones of high soil water content and root density did not coincide with the plant rows. However, some growers have found the furrow placement to reduce some of the disease problems normally experienced with the traditional furrow irrigation methods.

Mechanisms of cell division: lessons from a nematode

The mechanisms orchestrating spatial cell division control remain poorly understood. In animal cells, the position of the mitotic spindle dictates cleavage furrow placement, and thus plays a key role in governing spatial relationships between resulting daughter cells. The one-cell stage Caenorhabditis elegans embryo is an attractive model system to investigate the mechanisms underlying spindle positioning in metazoans. In this review, the experimental advantages of this model system for an in vivo dissection of cell division processes are first discussed. Next, three lines of experiments that were conducted to dissect the mechanisms governing spindle positioning in one-cell stage C. elegans embryos are summarized. First, localized laser micro-irradiations were utilized to identify the forces acting on spindle poles during anaphase. This work revealed that there is a precise imbalance of pulling forces acting on the two spindle poles, with the forces acting on the posterior spindle pole being in slight excess, thus explaining the asymmetric spindle position achieved by the end of anaphase. Second, an RNAi-based functional genomic screen was carried out to identify novel components required for generating these pulling forces. This uncovered that gpr-1/gpr-2, which encode GoLoco-containing proteins, as well as the previously identified Ga subunits goa-1/gpa-16, are required for generation of pulling forces on the spindle poles. Third, the zyg-8 locus was identified by mutational analysis to play a distinct role during anaphase spindle positioning. zyg-8 was found to encode a protein related to human Doublecortin, which is affected in patients with neuronal migration disorders. Moreover, ZYG-8 is a microtubule-associated protein that stabilizes microtubules against depolymerization. Together, these experimental approaches contribute to a better understanding of the mechanisms orchestrating spatial cell division control in metazoan organisms.

Epsilon-tubulin is an essential component of the centriole.

Centrioles and basal bodies are cylinders composed of nine triplet microtubule blades that play essential roles in the centrosome and in flagellar assembly. Chlamydomonas cells with the bld2-1 mutation fail to assemble doublet and triplet microtubules and have defects in cleavage furrow placement and meiosis. Using positional cloning, we have walked 720 kb and identified a 13.2-kb fragment that contains epsilon-tubulin and rescues the Bld2 defects. The bld2-1 allele has a premature stop codon and intragenic revertants replace the stop codon with glutamine, glutamate, or lysine. Polyclonal antibodies to epsilon-tubulin show peripheral labeling of full-length basal bodies and centrioles. Thus, epsilon-tubulin is encoded by the BLD2 allele and epsilon-tubulin plays a role in basal body/centriole morphogenesis.

Effect of jalshakti on growth and yield of finger millet (Eleusine coracana) and little millet (Panicum miliaceum) at plateau region of Bihar

The field experiment was conducted during the rainy seasons of 1986 and 1987 to study the response of jalshakti on growth and yield of finger millet [Eleusine coracunu (L.) Gaertn.] and little millet (Panicum miliaceuin L.) in marginal acidic sandy-loam soils at Ranchi. ~alshakti@ 4 kgha through furrow placement gave the maximum grain yield of finger millet. Application of jalshakti @ 8 kg~ha as furrow placement gave maximum grain yield of little millet, closely followed by jalshakti @ 10 g/kg seed as seed treatment + 8 kglha as furrow application. The increase in grain yields of finger millet and little millet due to application of jalshakti under different races and methods were 5.4-26.1 and 7.9-33.6% respectively. Only grain weightiear or panicle of 2 crops among yield components responded significantly to jalshakti. The highest values were recorded with jalshakti @ 4 kglha as ~ U & W placement + @ 20 g/kg seed as seed treatment and @ 8 kgha as furrow placement + @ 20 gl kg seed as seed treatment in finger millet and little millet respectively. This parameter finally con(ribu1ed to increased grain yield of the crops.

Effect of weed control and fertilizer placement on weeds, yield components and seed yield of Indian mustard (Brassica juncea)

A field experiment was conducted during winter (rabi) season of 1988-89 and 1989-90 at Jorhat, to find out effective method of weed control and fertilizer application to minimize weed interference for higher yield of Indian mustard [Brassica juncea (L.) Czernj. & Cosson]. Wheel-hoeing twice at 20 and 40 days af- ter seeding registered 50.3% weed-control efficiency and resulted in the highest seed yield (9.07,qha) by im- proving the yield components. This ww on a par with 2 hand-weedings. Furrow placement of fertilizer sig- nificantly reduced the weed-biomass production by 17.1%, which resulted in a significant increase of 15.2% in crop yield over broadcasting method of fertilizer application.

CYTOKINESIS IN CELLS UNDERGOING MITOSIS WITHOUT GENOME REPLICATION

Chinese hamster ovary cells can be forced to enter mitosis without prior DNA replication by treatment with hydroxyurea and caffeine. Cells treated in this way assemble a spindle that functions normally except that it does not accomplish anaphase spindle elongation (anaphase B). The chromatin detaches from the unreplicated kinetochores, which fragment, but establish microtubule attachments and migrate to the metaphase plate. Partitioning of the kinetochore fragments ensues on the normal schedule. Typical midbodies and cleavage furrows are established and daughter cells of equal size are produced. These results imply that intact chromosomes are not necessary for correct cleavage furrow placement but that kinetochores might be. Further, it is clear that cleavage furrow placement does not depend on anaphase spindle elongation.

Pharmacological and genetic evidence for a role of rootlet and phycoplast microtubules in the positioning and assembly of cleavage furrows in Chlamydomonas reinhardtii.

In Chlamydomonas reinhardtii, specialized cytoskeletal structures known as rootlet microtubules are present throughout interphase and mitosis. During cytokinesis, an array of microtubules termed the phycoplast is nucleated from rootlet microtubules and forms coincidentally with the cleavage furrow [Johnson and Porter, 1968: J. Cell Biol. 38:403-425; Holmes and Dutcher, 1989: J. Cell Sci. 94:273-285; Gaffel and el-Gammel, 1990: Protoplasma 156:139-148; Schibler and Huang, 1991: J. Cell Biol. 113:605-614]. We have obtained two independent lines of evidence that support the hypothesis that the rootlet and phycoplast microtubules play a direct role in cleavage furrow placement and assembly. First, the destabilization of spindle and phycoplast microtubules by pharmacological agents was accompanied by the aberrant distribution of actin and a failure of cytokinesis. Second, we characterized mutant strains that failed to complete cytokinesis properly. Actin and myosin were mislocalized to additional rootlet microtubules in the cyt2-1 strain, and this mislocalization was correlated with the presence of additional cleavage furrows. This evidence suggests that microtubules are necessary for the correct positioning and assembly of functional cleavage furrows in C. reinhardtii.

Corn Growth and Nitrogen Uptake with Furrow Irrigation and Fertilizer Bands

AbstractFurrow irrigation is commonly used to provide supplemental water to row crops. Alternate‐furrow irrigation has been proposed as a method to decrease deep percolation water losses as well as the leaching of fertilizer and pesticides. A study was conducted on a Ulm clay loam (fine, smectitic, mesic Ustic Haplargids) in 1994 and 1995 near Fort Collins, CO. Corn (Zea mays L.) growth and N uptake were measured under alternate‐furrow and every‐furrow irrigation water applications, each with fertilizer bands placed either in the row or in the furrow. Nitrogen‐15‐depleted (NH4)2SO4 fertilizer was used to distinguish plant uptake of fertilizer N from uptake of naturally occurring N. There were no differences in plant response to alternate‐furrow or every‐furrow irrigation water placement for the same amount of water applied. Greater fertilizer‐N uptake occurred with row placement than with furrow placement of N fertilizer. Early in the growing season, fertilizer‐N uptake from row placement was from 2 to 10 times the fertilizer‐N uptake from furrow placement. By the end of the growing season, the average total‐N uptake from row placement was 12% greater than for furrow placement. Placing the fertilizer in the nonirrigated furrow of the alternate‐furrow irrigation treatment decreased N availability by 20% compared with the average of the other treatments. If alternate‐furrow irrigation is used to increase water use efficiency in furrow‐irrigated fields, placing the N fertilizer in the nonirrigated furrow of the alternate‐furrow irrigation system could decrease N availability because of drier soil conditions in the nonirrigated furrow. Row placement of N fertilizer seems to be beneficial in both alternate‐furrow and every‐furrow irrigation applications.

Loss of spatial control of the mitotic spindle apparatus in a Chlamydomonas reinhardtii mutant strain lacking basal bodies.

The bld2-1 mutation in the green alga Chlamydomonas reinhardtii is the only known mutation that results in the loss of centrioles/basal bodies and the loss of coordination between spindle position and cleavage furrow position during cell division. Based on several different assays, bld2-1 cells lack basal bodies in > 99% of cells. The stereotypical cytoskeletal morphology and precise positioning of the cleavage furrow observed in wild-type cells is disrupted in bld2-1 cells. The positions of the mitotic spindle and of the cleavage furrow are not correlated with respect to each other or with a specific cellular landmark during cell division in bld2-1 cells. Actin has a variable distribution during mitosis in bld2-1 cells, but this aberrant distribution is not correlated with the spindle positioning defect. In both wild-type and bld2-1 cells, the position of the cleavage furrow is coincident with a specialized set of microtubules found in green algae known as the rootlet microtubules. We propose that the rootlet microtubules perform the functions of astral microtubules and that functional centrioles are necessary for the organization of the cytoskeletal superstructure critical for correct spindle and cleavage furrow placement in Chlamydomonas.

Corn Production Using Alternate Furrow Nitrogen Fertilization and Irrigation

Any overwatering associated with surface furrow irrigation can reduce N fertilizer use efficiency. This 3-yr study was conducted to determine whether an irrigation and fertilizer placement system that puts water and N fertilizer in adjacent furrows could improve corn (Zea mays L.) grain yields by improving N fertiliser use efficiency. The effects of irrigation placement, N fertilizer placement, and N quantities on several plant parameters and yield were investigated at Portageville, MO, on a Tiptonville silt loam (fine-silty, mixed, thermic Typic Arguidoll). Corn grain yields were increased in each year of the study by placing irrigation water in every furrow. Placement of N in alternate furrows produced yields equal to every furrow placement in 1991 and 1992, and an 8.4 bu/acre increase in 1993, despite enbanced early season growth from N placement in every fumors. For corn production under southeast Missouri conditions, it appears necessary to improve the irrigation effectiveness of the alternate furrow system before the benefits of alternate furrow fertilization placement can be fully used

Leaching and Water Flow Patterns in Every‐Furrow and Alternate‐Furrow Irrigation

AbstractDeep water percolation and chemical leaching is a recognized environmental problem with furrow irrigation. Alternate‐furrow irrigation (AFI) was hypothesized as a method to increase water‐use efficiency and decrease chemical leaching compared with every‐furrow irrigation (EFI). The SWMS_2D finite‐element model was used to investigate water and CaCl2 movement in EFI and AFI with furrow‐placed or ridge‐placed fertilizer bands. Model simulations were conducted for a Crook loamy sand (mixed, mesic, Ustic Torripsamment) and a Nunn clay loam (fine, montmorillonitic, mesic Aridic Argiustoll). Water isolation zones occurred with AFI and EFI that contributed little to overall profile drainage. The soil water contents after infiltration and redistribution were more uniform for EFI than for AFI for both soils. Water distribution was more uniform with AFI in the clay loam than in the loamy sand. Chemical movement was least with AFI and CaCl2 placement under the nonirrigated furrow. The greatest chemical leaching was predicted with furrow placement of CaCl2 and EFI. Results with CaCl2 suggest soluble chemicals or fertilizers placed under the nonirrigated furrow in loamy sand may not be available for plant uptake because the soil did not wet during irrigation. With either form of furrow irrigation, placement of a fertilizer in the ridge rather than in the furrow would decrease leaching of the fertilizer and keep the fertilizer in the root zone.