Dynamics of Competition in Populations of Carrot (Daucus carota)

Populations of carrot (Daucus carota) were raised over a widerange of densities (79–5763 plants m^-2) to examine thedynamics of competition in terms of yield–density relationshipsand size variability, and to investigate the effects of nutrientsupply on competition. While the relationship between shootyield and density was asymptotic, the relationship between rootand total yield and density tended to be parabolic. For a giventime and density series the relationship between yield per unitarea and density could best be described by the model: y=w_mD_(1+aD)^b wherey is the yield per unit area,D is density,w_m, a andb arefitted parameters. The parametersw_m anda increased over timebut nutrient availability affected onlyw_m. An extension of thebasic yield-density model is proposed to describe the dynamicsof the yield–density relationship over time: y=kD_{[1+cexp(-rt)]{1+}     

A new species of Galearis (Orchidinae: Orchidaceae) from Sichuan,China

A new species, Galearis huanglongensis Q.W.Meng & Y.B.Luo, is described and illustrated. It is similar to Galearis cyclochila (Franch. & Sav.) Soó and Galearis diantha (Schltr.) P.F.Hunt, but differs in having a short spur, two elliptical lateral stigma lobes and distinctly separated bursicles. This new species is known only from the type locality, the Huanglong Valley, Songpan County, western Sichuan, China, growing amongst mosses under alpine shrubs at an elevation of about 3000 m. Based on two years of observations of its population size, the species was categorized as critically endangered CR (B1a, B2a) according to the World Conservation Union (IUCN) Red List Categories and Criteria, Version 3.1. The micromorphology of pollinia and seeds was observed by scanning electron microscopy and compared with that of G. cyclochila and G. diantha. The results supported G. huanglongensis Q.W.Meng & Y.B.Luo as a new species. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 689–695.     

Unravelling mitochondrial retrograde regulation in the abiotic stress induction of rice ALTERNATIVE OXIDASE 1 genes

Mitochondrial retrograde regulation (MRR) is the transduction of mitochondrial signals to mediate nuclear gene expression. It is not clear whether MRR is a common regulation mechanism in plant abiotic stress response. In this study, we analysed the early abiotic stress response of the rice OsAOX1 genes, and the induction of OsAOX1a and OsAOX1b (OsAOX1a/b) was selected as a working model for the stress‐induced MRR studies. We found that the induction mediated by the superoxide ion (O_2·^‐)‐generating chemical methyl viologen was stronger than that of hydrogen peroxide (H₂O₂). The addition of reactive oxygen species (ROS) scavengers demonstrated that the stress induction was reduced by eliminating O_2·^‐. Furthermore, the stress induction did not rely on chloroplast‐ or cytosol‐derived O_2·^‐. Next, we generated transgenic plants overexpressing the superoxide dismutase (SOD) gene at different subcellular locations. The results suggest that only the mitochondrial SOD, OsMSD, attenuated the stress induction of OsAOX1a/b specifically. Therefore, our findings demonstrate that abiotic stress initiates the MRR on OsAOX1a/b and that mitochondrial O_2·^– is involved in the process.     

Bone marrow–derived mesenchymal stromal cells ameliorate severe acute pancreatitis in rats via hemeoxygenase-1–mediated anti-oxidant and anti-inflammatory effects

Background and aims

It has been previously verified that mesenchymal stromal cells (MSCs) have a good therapeutic effect on severe acute pancreatitis (SAP) and the potential for regeneration of damaged pancreatic tissue, but the exact molecular mechanism remains unclear. In this study, we demonstrated the therapeutic effect of bone morrow MSCs (BMSCs) on SAP, probably by targeting heme oxygenase-1 (HO-1).

Insulin-like growth factor 2 regulates the proliferation and differentiation of rat adipose-derived stromal cells via IGF-1R and IR

BackgroundInsulin-like growth factor 2 (IGF2), an essential component of the stem cell niche, has been reported to modulate the proliferation and differentiation of stem cells. Previously, a continuous expression of IGF2 in tissues was reported to maintain the self-renewal ability of several types of stem cells. Therefore, in this study, we investigated the expression of IGF2 in adipose tissues and explored the effects of IGF2 on adipose-derived stromal cells (ADSCs) in vitro.MethodsThe expression pattern of IGF2 in rat adipose tissues was determined by gene expression and protein analyses. The effect of IGF2 on proliferation, stemness-related marker expression and adipogenic and osteogenic differentiation was systematically investigated. Furthermore, antagonists of IGF2-specific receptors—namely, BMS-754807 and picropodophyllin—were added to explore the underlying signal transduction mechanisms.ResultsIGF2 levels displayed a tendency to decrease with age in rat adipose tissues. After the addition of IGF2, isolated ADSCs displayed higher proliferation and expression of the stemness-related markers NANOG, OCT4 and SOX2 and greater differentiation potential to adipocytes and osteoblasts. Additionally, both type 1 insulin-like growth factor receptor (IGF-1R) and insulin receptor (IR) participated in the IGF2-mediated promotion of stemness in ADSCs.ConclusionsOur findings indicate that IGF2 could enhance the stemness of rat ADSCs via IGF-1R and IR and may highlight an effective method for the expansion of ADSCs for clinical application.     

SRAP、ISSR技术的优化及在甘蓝类植物种子鉴别中的应用

将SRAP与ISSR 2种分子标记技术应用于8种甘蓝类植物（Brassica oleracea L.）的种子鉴别中。先以甘蓝（Brassica oleracea var. capitata）基因组DNA为模板,通过对SRAP、ISSR反应体系中各影响因素的逐一筛选,优化了甘蓝类植物SRAP、ISSR反应体系。进而采用30个SRAP引物组合和15个ISSR引物对白甘蓝、皱叶甘蓝、红甘蓝、羽衣甘蓝、花椰菜、青花菜、抱子甘蓝、球茎甘蓝的基因组DNA进行了PCR扩增,结果表明：M3E5与M4E5两个SRAP引物组合可以在8种甘蓝类植物之间显示较高的多态性;844和888两个ISSR引物也可在8种甘蓝类植物之间产生很好的多态,特别是844引物单独应用即可区分所有材料。     

Fifteen polymorphic simple sequence repeat markers from expressed sequence tags of Liriodendron tulipifera

We developed and evaluated simple sequence repeat (SSR) markers derived from expressed sequence tags (ESTs) of Liriodendron tulipifera. Characteristics of 15 EST‐SSR loci were investigated using 33 L. tulipifera individuals. The number of alleles per locus ranged from two to five. The expected and observed heterozygosities ranged from 0.216 to 0.751 and from 0.182 to 0.97, respectively. These loci were further tested for their cross‐species transferability to Liriodendron Chinense. Because of their high level of polymorphism and transferability, our 15 single‐locus EST‐SSR markers will be valuable tools for research on mating system, population genetics and systemic evolution of Liriodendron.