Identification of Dw1, a Regulator of Sorghum Stem Internode Length

Sorghum is an important C4 grain and grass crop used for food, feed, forage, sugar, and biofuels. In its native Africa, sorghum landraces often grow to approximately 3–4 meters in height. Following introduction into the U.S., shorter, early flowering varieties were identified and used for production of grain. Quinby and Karper identified allelic variation at four loci designated Dw1-Dw4 that regulated plant height by altering the length of stem internodes. The current study used a map-based cloning strategy to identify the gene corresponding to Dw1. Hegari (Dw1dw2Dw3dw4) and 80M (dw1dw2Dw3dw4) were crossed and F₂ and HIF derived populations used for QTL mapping. Genetic analysis identified four QTL for internode length in this population, Dw1 on SBI-09, Dw2 on SBI-06, and QTL located on SBI-01 and SBI-07. The QTL on SBI-07 was ~3 Mbp upstream of Dw3 and interacted with Dw1. Dw1 was also found to contribute to the variation in stem weight in the population. Dw1 was fine mapped to an interval of ~33 kbp using HIFs segregating only for Dw1. A polymorphism in an exon of Sobic.009G229800 created a stop codon that truncated the encoded protein in 80M (dw1). This polymorphism was not present in Hegari (Dw1) and no other polymorphisms in the delimited Dw1 locus altered coding regions. The recessive dw1 allele found in 80M was traced to Dwarf Yellow Milo, the progenitor of grain sorghum genotypes identified as dw1. Dw1 encodes a putative membrane protein of unknown function that is highly conserved in plants.     

Genotypic covariations of traits underlying sorghum stem biomass production and quality and their regulations by water availability: Insight from studies at organ and tissue levels

Sweet and biomass sorghum are expected to contribute increasingly to bioenergy production. Better understanding the impacts of the genotypic and environmental variabilities on biomass component traits and their properties is essential to optimize energy yields. This study aimed to evaluate whether traits contributing to stem biomass growth and biochemical composition at different biological scales (co)vary with the genotype and the water status in sorghum. Height genotypes were studied over two years in field conditions in southern France under two water treatments (well watered vs. 25 days’ dry down during stem elongation). Main stem internode number, size, (non)structural carbohydrate, and lignin contents were measured at the end of the stress period and/or at final harvest, together with biochemical and histological analyses of the youngest expanded internode. The tallest genotypes showed the highest stem dry weights and lignin contents. Stem (structural) biomass density was positively correlated with lignin content, particularly in internode parenchyma. Stem soluble sugar and lignin contents were inversely proportional across genotypes and water conditions. Genotypes contrasted for drought sensitivity and recovery capacity of stem growth and biochemical composition. The length and cell wall deposition of internodes expanding under water deficit were reduced and did not recover, these responses being weakly correlated. Genotypic variability was pointed out in the growth recovery of internodes expanding under re‐watered conditions. According to the observed genotypic variability and the absence of antagonistic correlations between the responses of the different traits to water availability, it is suggested that biomass sorghum varieties optimizing their responses to water availability in terms of growth and cell wall deposition can be developed for different bioenergy targets.     

Mouse 3T3 fibroblasts under the influence of fibroblasts isolated from stroma of human basal cell carcinoma acquire properties of multipotent stem cells

Background information. Multipotent mesenchymal stem cells can participate in the formation of a microenvironment stimulating the aggressive behaviour of cancer cells. Moreover, cells exhibiting pluripotent ESC (embryonic stem cell) markers (Nanog and Oct4) have been observed in many tumours. Here, we investigate the role of cancer‐associated fibroblasts in the formation of stem cell supporting properties of tumour stroma. We test the influence of fibroblasts isolated from basal cell carcinoma on mouse 3T3 fibroblasts, focusing on the expression of stem cell markers and plasticity in vitro by means of microarrays, qRT‐PCR (quantitative real‐time PCR) and immunohistochemistry. Results. We demonstrate the biological activity of the cancer stromal fibroblasts by influencing the 3T3 fibroblasts to express markers such as Oct4, Nanog and Sox2 and to show differentiation potential similar to mesenchymal stem cells. The role of growth factors such as IGF2 (insulin‐like growth factor 2), FGF7 (fibroblast growth factor 7), LEP (leptin), NGF (nerve growth factor) and TGFβ (transforming growth factor β), produced by the stromal fibroblasts, is established to participate in their bioactivity. Uninduced 3T3 do not express the stem cell markers and show minimal differentiation potential. Conclusions. Our observations indicate the pro‐stem cell activity of cancer‐associated fibroblasts and underline the role of epithelial—mesenchymal interaction in tumour biology.     

How internode length,position and presence of leaves affect survival and growth of <Emphasis Type="Italic">Alternanthera philoxeroides</Emphasis> after fragmentation?

Disturbance is common in nature and disturbance-caused fragmentation of clones happens frequently in stoloniferous plants. After fragmentation storage in stolon internodes and leaves may enhance survival and growth of stoloniferous plants. We hypothesize that (1) increasing length of the internode attached to the ramet and (2) presence of leaves will increase ramet survival and growth, and that (3) internode positions (before or after the ramet or both) will also play a role. We tested these hypotheses with the stoloniferous, invasive herb Alternanthera philoxeroides. In one experiment, we measured survival and growth of the ramets either without stolon internode (0 cm in length) or attached with internodes of 2, 4, 6 and 8 cm and either with or without leaves. In the other experiment, we measured survival and growth of the ramets attached with a proximal internode (before the ramet), a distal internode (after the ramet) or both. Increasing internode length and presence of leaves significantly increased the survival rate and growth (biomass, leaf area, number of ramets, stolon length and number of leaves) of the A. philoxeroides plants. All growth measures of A. philoxeroides at harvest were larger when the ramets were attached with a distal internode than when they were attached with a proximal internode, but the survival rate was lower. These results support the hypotheses and suggest that storage in stolons and leaves may be of great significance for clonal plants in frequently disturbed habitats and may contribute greatly to the invasiveness of A. philoxeroides.     

Inhibition of cell growth by cellular differentiation into adipocyte-like cells in dexamethasone sensitive cancer cell lines

The stress responses in human body lead to secretion of cortisol hormone. The present study investigated the cellular responses on cell growth and cellular differentiation into adipocytes by exposure of synthetic stress hormone, dexamethasone (DEX) in various human cancer and normal cells. After prolonged exposure of cells with 1?μg/ml DEX for 2 weeks, population doubling time (PDT) was significantly (P?P?P?β (GRβ) and peroxisome proliferator-activated receptor γ (PPARγ) were significantly (P?P?相似文献   

Sucrose accumulation in sweet sorghum stem internodes in relation to growth

Sweet sorghum (Sorghum bicolor L. Moench) stems of different cultivars (NK 405. Keller and Tracy) reveal a different pattern of sucrose accumulation with respect to in-ternodal sugar content and distribution. The onset of sucrose storage is not necessarily associated with the reproductive stage of the plant, as was hitherto assumed, but obviously occurs after cessation of internodai elongation as was postulated for the sugarcane stem. For at least two of the three cultivars, ripening is an internode to internode process beginning at the lowermost culm parts. Intensive growth of the internodes, combined with a high hexose content in stern parenchyma, shows a strong positive correlation (r |Mg 0.94) to the activity of sucrose synthase (SuSy; EC 2.4.13), but not to invertase (EC 3.2.1.26) which is not present as soluble (neutral and acid) or cell wall-bound, salt-extractable enzyme in the three culsivars investigated. Sucrose synthase measured in sucrose cleavage and synthesis direction reveals divergent activity rates and sensitivity towards exogenously applied Mg²⁺ ions and pH. SuSy activity is connected to the increase of internodai sucrose content in so far as (1) its decline is a prerequisite for the onset of sucrose accumulation and (2) it remains at a constant low level during sucrose storage. Sucrose phosphate synthase (SPS; EC 2.4.1.14) activity in the sorghum stem is low compared to SuSy and uniformly distributed over all inter-nodes. Only source leaves of sorghum show a considerable SPS activity, but neither stem nor leaf SPS reveal a positive correlation to the increase of internodai sucrose content. Sucrose phosphate phosphatase (SPP; EC 3.1.3.24) amounts lo only 24–30% of the respective SPS activity but follows the same distribution pattern. None of the enzymes under study proves to be responsible for the extent of sucrose storage in the stem, so other phenomena such as transport processes within the stern tissue require further investigation.     

Effects of gibberellin on the cellular dynamics of dwarf pea internode development

This study analysed the dynamics of cell production and extension, and how these were affected by applied gibberellic acid (GA₃), during internode development in dwarf peas (Pisum sativum L. cv. Meteor). Image analysis was used to obtain cell number and length data for entire cell columns along the epidermis, the two outermost cortical layers, and the pith, from internode 7, over a time period covering the whole of the internode's growth phase. For a few days following the inception of an internode at the shoot apex, little further growth occurred, and there was no significant effect of GA₃ on cell division or cell extension. The subsequent growth of the internode was stimulated more than fourfold by GA₃ as a result of the production of more than twice the number of cells, which were twice as long. At least 96.5% of the cells of the mature internode were actually formed within the internode itself during this period of growth, demonstrating that the internode cells themselves represent the morphogenetic site of response to GA₃. Mitoses and cell extension occurred along the full length of the internode throughout its development. The daily changes in cell numbers were modelled by the Richards function, and manipulations of the fitted functions to reveal time trends of absolute and specific cell production rates were performed for each stem tissue. The increase in cell numbers in the +GA₃ plants was brought about by an increase in the rate of cell production, over a shorter time interval; specific cell production rates declined continuously from initial rapid rates in the +GA₃ epidermis and pith, but declined more slowly in the cortex. The control (−GA₃) epidermis and cortex cells exhibited a constant specific cell production rate (i.e. purely exponential) for several days. Cell extension rates were calculated so as to compensate for the size-reduction effects of concurrent cell division. These calculations confirmed that `real' cell extension rates were higher in the +GA₃ internodes. Models of the cellular controls of internode growth, based on the estimated dynamics of cell division and extension, are discussed. Received: 1 July 1997 / Accepted: 30 July 1997     

Agronomic Considerations for Sweet Sorghum Biofuel Production in the South-Central USA

Sweet sorghum (Sorghum bicolor (L.) Moench) is currently recognized throughout the world as a highly promising biomass energy crop. Production systems and management practices for sweet sorghum have not been fully developed for the USA, although sporadic research efforts during recent decades have provided some insights into production of sweet sorghum primarily for fermentable sugar production. Field plot experiments were conducted at sites across Louisiana to assess biomass and sugar yield responses to N fertilizer, plant density, and selected cultivars. Although linear increases in stem biomass production and fermentable sugar yield were obtained with increasing N fertilizer rate under irrigated conditions, most of the increase was from the initial 45 kg N ha⁻¹ increment. Nitrogen fertilization increased stem biomass production but not fermentable sugar yield in some non-irrigated environments. Increased plant density contributed to fermentable sugar yield only under growth-limiting conditions, particularly under limited soil moisture. Location effects indicate that sweet sorghum may not be suitable for some sub-optimal cropland and pasture environments in Louisiana. During the primary growing season, cultivar did not affect fermentable sugar yields, although Dale was consistently high in sugar concentration during this period. Nitrogen fertilizer increased fermentable sugar yields only when moisture was not limiting. Overall results indicate that in environments where soil moisture limits plant growth, sugar yield responses are likely from increased plant density and not from increased N fertilization.     

Effects of leaf and branch removal on carbon assimilation and stem wood density of Eucalyptus grandis seedlings

The rate of leaf CO₂ assimilation (A _l) and leaf area determine the rate of canopy CO₂ assimilation (A _c) can be thought proportional to assimilate supply for growth and structural requirements of plants. Partitioning of biomass within plants and anatomy of cells within stems can determine how assimilate supply affects both stem growth and wood density. We examined the response of stem growth and wood density to reduced assimilate supply by pruning leaf area. Removing 42% of the leaf area of Eucalyptus grandis Hill ex Maiden seedlings did not stimulate leaf-level photosynthesis (A _l) or stomatal conductance, contrary to some previous studies. Canopy-level photosynthesis (A _c) was reduced by 41% immediately after pruning but due almost solely to continued production of leaves, and was only 21% lower 3 weeks later. Pruning consequently reduced seedling biomass by 24% and stem biomass by 18%. These reductions in biomass were correlated with reduced A _c. Pruning had no effect on stem height or diameter and reduced wood density to 338 kg m⁻³ compared to 366 kg m⁻³ in control seedlings. The lower wood density in pruned seedlings was associated with a 10% reduction in the thickness of fibre cell walls, and as fibre cell diameter was invariant to pruning, this resulted in smaller lumen diameters. These anatomical changes increased the ratio of cross-sectional area of lumen to area cell wall material within the wood. The results suggest changes to wood density following pruning of young eucalypt trees may be independent of tree volume and of longer duration.     

The role of a class III gibberellin 2‐oxidase in tomato internode elongation

A network of environmental inputs and internal signaling controls plant growth, development and organ elongation. In particular, the growth‐promoting hormone gibberellin (GA) has been shown to play a significant role in organ elongation. The use of tomato as a model organism to study elongation presents an opportunity to study the genetic control of internode‐specific elongation in a eudicot species with a sympodial growth habit and substantial internodes that can and do respond to external stimuli. To investigate internode elongation, a mutant with an elongated hypocotyl and internodes but wild‐type petioles was identified through a forward genetic screen. In addition to stem‐specific elongation, this mutant, named tomato internode elongated ‐1 (tie‐1) is more sensitive to the GA biosynthetic inhibitor paclobutrazol and has altered levels of intermediate and bioactive GAs compared with wild‐type plants. The mutation responsible for the internode elongation phenotype was mapped to GA2oxidase 7, a class III GA 2‐oxidase in the GA biosynthetic pathway, through a bulked segregant analysis and bioinformatic pipeline, and confirmed by transgenic complementation. Furthermore, bacterially expressed recombinant TIE protein was shown to have bona fide GA 2‐oxidase activity. These results define a critical role for this gene in internode elongation and are significant because they further the understanding of the role of GA biosynthetic genes in organ‐specific elongation.     

Three AtCesA6‐like members enhance biomass production by distinctively promoting cell growth in Arabidopsis

Cellulose is an abundant biopolymer and a prominent constituent of plant cell walls. Cellulose is also a central component to plant morphogenesis and contributes the bulk of a plant's biomass. While cellulose synthase (CesA) genes were identified over two decades ago, genetic manipulation of this family to enhance cellulose production has remained difficult. In this study, we show that increasing the expression levels of the three primary cell wall AtCesA6‐like genes (AtCesA2, AtCesA5, AtCesA6), but not AtCesA3, AtCesA9 or secondary cell wall AtCesA7, can promote the expression of major primary wall CesA genes to accelerate primary wall CesA complex (cellulose synthase complexes, CSCs) particle movement for acquiring long microfibrils and consequently increasing cellulose production in Arabidopsis transgenic lines, as compared with wild‐type. The overexpression transgenic lines displayed changes in expression of genes related to cell growth and proliferation, perhaps explaining the enhanced growth of the transgenic seedlings. Notably, overexpression of the three AtCesA6‐like genes also enhanced secondary cell wall deposition that led to improved mechanical strength and higher biomass production in transgenic mature plants. Hence, we propose that overexpression of certain AtCesA genes can provide a biotechnological approach to increase cellulose synthesis and biomass accumulation in transgenic plants.     

典型草原围封后羊草地上功能性状对枯落物累积的响应

植物功能性状反映植物适应环境变化过程中在不同器官形态与功能间的资源权衡与分配策略。典型草原围封后枯落物累积导致群落光照、热量和水分的重新分配并改变微环境特征。在此过程中植物地上功能性状将通过怎样的变化来适应新的环境,目前尚不清楚。2015—2017年每年8月对内蒙古地区3种典型草原共有物种羊草（Leymus chinensis）的植株、叶片和茎干功能性状进行了测量与分析。结果表明：枯落物累积显著增加了羊草的植株高度、单株重量、茎叶比和总叶面积;枯落物累积显著增加了羊草的叶片长度、叶片重量、单叶面积、节间长度和茎干重量,这些性状属于敏感性状;枯落物累积对羊草的叶片数量和节间数量无显著影响,相对而言,这些性状属于惰性性状;羊草的单株重量与植株高度、叶片重量呈极显著的正相关关系（P<0.0001）;羊草的植株高度与节间数量、节间长度呈极显著的正相关关系（P<0.0001）。本研究结果从植物地上功能性状的角度阐明了典型草原植物对环境变化的适应方式,可为围封草原的合理管理提供基础数据与理论依据。     

Responses of elongation growth rate,turgor pressure and cell wall extensibility of stem cells of Impatiens balsamina to lead,cadmium and zinc

Elongation growth rate of stem cells of Impatiens balsamina was inhibited by the heavy metals Pb²⁺, Cd²⁺ and Zn²⁺ due to their suppression on cell wall extensibility. Effective turgor was also inhibited by Pb²⁺ and Cd²⁺ but it played a secondary role in reducing the stem cell elongation growth rate. The major rate-limiting factor for cell elongation growth was the cell wall extensibility. Furthermore, Cd²⁺ was found to be more toxic than Pb²⁺, while Pb²⁺ was more toxic than Zn²⁺.     

Fracture mechanics of the cell wall of Chara corallina

Previous mechanical studies using algae have concentrated on cell extension and growth using creep-type experiments, but there appears to be no published study of their failure properties. The mechanical strength of single large internode cell walls (up to 2 mm diameter and 100 mm in length) of the charophyte (giant alga) Chara corallina was determined by dissecting cells to give sheets of cell wall, which were then notched and fractured under tension. Tensile tests, using a range of notch sizes, were conducted on cell walls of varying age and maturity to establish their notch sensitivity and to investigate the propagation of cracks in plant cell walls. The thickness and stiffness of the walls increased with age whereas their strength was little affected. The strength of unnotched walls was estimated as 47 ± 13 MPa, comparable to that of some grasses but an order of magnitude higher than that published for model bacterial cellulose composite walls. The strength was notch-sensitive and the critical stress intensity factor K _1c was estimated to be 0.63 ± 0.19 MNm^−3/2, comparable to published values for grasses. Received: 4 April 2000 / Accepted: 21 July 2000     

不同水分处理对狗牙根种内相互作用的影响

以狗牙根当年生扦插苗为试验材料,根据库区河岸带水分特征设置4种水分处理方式:水分对照组(CK)、水淹与干旱交替组(FD)、土壤水分饱和组(LF)和全淹组(FL),4种密度方式:对照(1株/盆)、低密度(2株/盆)、中密度(4株/盆)及高密度(12株/盆),探究狗牙根生长及形态响应,并验证胁迫梯度假说。结果表明:(1)狗牙根各生物量随水分胁迫强度的增加显著下降(P0.001);密度处理和二者交互作用显著影响狗牙根叶干重、茎干重、根干重、地上生物量和总生物量(P0.001)。(2)水分处理显著影响狗牙根各形态指标(P0.001);密度和二者交互作用显著影响狗牙根分枝数、总茎长和节间长(P0.001)。(3)CK组和LF组狗牙根生物量相对邻体效应(RNE)均为负值,表明其种内关系为竞争关系。FL组各密度组生物量RNE值均为正值,其种内关系转化为促进关系。(4)中高密度组总茎长RNE值随水分胁迫增加而增大。研究表明:(1)狗牙根对不同的水分胁迫均表现出积极响应,可考虑将狗牙根用于库区河岸带植被重建。(2)随种植密度的增大,狗牙根生长及形态均表现出一定的负面效应。(3)本试验在一定程度上支持胁迫梯度假说,但尚需更多概念模型将其改进完善。