ARP2/3 complex‐mediated actin dynamics is required for hydrogen peroxide‐induced stomatal closure in Arabidopsis

Multiple cellular events like dynamic actin reorganization and hydrogen peroxide (H₂O₂) production were demonstrated to be involved in abscisic acid (ABA)‐induced stomatal closure. However, the relationship between them as well as the underlying mechanisms remains poorly understood. Here, we showed that H₂O₂ generation is indispensable for ABA induction of actin reorganization in guard cells of Arabidopsis that requires the presence of ARP2/3 complex. H₂O₂‐induced stomatal closure was delayed in the mutants of arpc4 and arpc5, and the rate of actin reorganization was slowed down in arpc4 and arpc5 in response to H₂O₂, suggesting that ARP2/3‐mediated actin nucleation is required for H₂O₂‐induced actin cytoskeleton remodelling. Furthermore, the expression of H₂O₂ biosynthetic related gene AtrbohD and the accumulation of H₂O₂ was delayed in response to ABA in arpc4 and arpc5, demonstrating that misregulated actin dynamics affects H₂O₂ production upon ABA treatment. These results support a possible causal relation between the production of H₂O₂ and actin dynamics in ABA‐mediated guard cell signalling: ABA triggers H₂O₂ generation that causes the reorganization of the actin cytoskeleton partially mediated by ARP2/3 complex, and ARP2/3 complex‐mediated actin dynamics may feedback regulate H₂O₂ production.     

油菜终花后角果和叶片光合对籽粒产量和品质的影响

以‘秦优7号’油菜品种为材料,设置叶片和角果遮光及摘除叶片处理,通过田间试验测定分析终花后角果和叶片的光合特性及其对籽粒产量、含油量及脂肪酸组成的影响。结果显示:(1)终花后油菜角果遮光使籽粒的千粒重、产量、含油量分别显著降低54.7%、62.1%、44.2%,且籽粒中硫甙含量及脂肪酸中棕榈酸、硬脂酸含量显著升高,亚麻酸含量显著降低。(2)叶片遮光和摘除叶片分别显著降低角粒数11.7%、11.3%,降低籽粒千粒重22.5%、17.9%,单株产量分别降低35.3%、44.7%,使籽粒脂肪酸中亚油酸、亚麻酸等含量显著增加,但对籽粒含油量无显著影响。(3)终花后油菜绿色角果皮最大面积是绿叶面积的1.54倍,角果叶绿素a、b以及类胡萝卜素含量显著低于叶片,但角果的净光合速率、蒸腾速率显著高于叶片;且角果层的光辐射强度显著高于角果层下的叶片层;角果响应光辐射强度的光补偿点、光饱和点均显著高于叶片;即角果能够适应较高强度光辐射环境。研究发现,油菜结角期角果层接受大部分光辐射,角果的光合活性显著高于叶片,是主要的光合器官,角果光合状况对籽粒产量、含油量及脂肪酸组成有显著影响。     

黄鳝单条染色体的显微分离及特异性检测

建立了显微分离黄鳝单条染色体及检测其特异性的方法;在Olympus倒置显微镜下用毛细玻璃微针手工分离黄鳝减数分裂Ⅰ终变期3号染色体,将期DNA作模板进行DOP-PCR扩增后,分别以α^-32P-dCTP和Biotin-11-dUTP标记的单条染色体DNAPCR扩增产物及Biotin-11-dUTP标记的大豆18SrRNA基因作探针进行Southern杂交,FISH和Dot杂交来检测其特异性,结果表明：（1）减数分裂Ⅰ终变期染色体标本是进行染色体显微操作的理想材料;（2）DOP-PCR扩增产物片段在200-1000bp之间,平均600bp左右;（3）杂交结果显示,本研究所获得的单条染色体是黄鳝3号染色体;（4）与显微操作仪和微激光分离相比较。该方法不需要昂贵仪器,在常规实验室即可操作,具有广泛的普及应用意义。     

Association between SSR markers and fibre traits in sea island cotton (<Emphasis Type="BoldItalic">Gossypium barbadense</Emphasis>) germplasm resources

Identification of molecular markers associated with fibre traits can accelerate cotton marker-assisted selection (MAS) programmes. In this study, Gossypium barbadense germplasm accessions with diverse origins (\(n = 123\)) were used to perform association analysis of fibre traits with 120 polymorphic simple sequence repeat (SSR) markers. In total, 120 polymorphic primer pairs amplified 258 loci with a mean of 2.15 loci per primer. Population structure analysis identified three main clusters for the accessions, which indicated agreement of genetic and predefined populations. Marker–trait associations (\(n= 58\)) were detected for 10 fibre traits with 26 SSR markers located on 15 chromosomes. The \(R^{2}\) (phenotypic variation explained) ranged from 3.19 to 15.21%. Two markers (NAU5465 and NAU3013) were found to be stably associated with boll number per plant (BNP) and fibre uniformity (UI), respectively. Four markers (BNL252, NAU3424, NAU3324 and CGR5202) associated with fibre quality traits preferentially clustered on the D8 chromosome, which was thus identified as an important candidate region for study molecular mechanisms underlying fibre quality and for use in breeding cotton cultivars for improving fibre quality. This study generated molecular data with a potential for better understanding of the genetic basis of the fibre traits and provided new markers for MAS in G. barbadense breeding programmes.     

Patchy distributions of Spirogyra arcta do not affect growth of the submerged macrophyte Ceratophyllum demersum

Spatial heterogeneity is common in aquatic conditions, but few studies have examined the effects of heterogeneous distributions of biological factors on aquatic plants. Spirogyra (Spirogyra arcta) coexists with many submerged macrophytes, such as Ceratophyllum demersum, but no study has examined the effects of heterogeneous distributions of spirogyra on the growth of submerged plants. We grew the submerged plant C. demersum in three homogeneous, aquatic conditions (0, 50 and 100% of the water surface in the container was evenly covered by spirogyra, referred to as ‘control’, ‘50%’ and ‘100%’, respectively) and two patchy conditions (the left half of the water surface in the container was not covered by spirogyra and 50% and 100% of the water surface in the right half of the container was evenly covered by spirogyra, referred to as ‘50%‐patchy’ and ‘100%‐patchy’, respectively). Compared with the control, the 100% treatment greatly decreased the biomass and number of ramets of C. demersum, but the 50% treatment did not. Growth of C. demersum in the left half of the container did not differ significantly between the control and the two heterogeneous treatments (50%‐patchy and 100%‐patchy). In addition, growth of C. demersum in the right half of the container did not differ between the 100% and the 100%‐patchy treatment or between the 50% and the 50%‐patchy treatment. Our results suggest that C. demersum can tolerate shading by spirogyra to a certain extent and that heterogeneous distributions of spirogyra do not affect its growth.     

Phosphate Uptake and Root Electrical Potential

It is shown that the potential difference between the rootsof five plant species and their external solution is relatedto the ionic strength of the solution in a logarithmic fashionas predicted by diffuse double-layer theory. The slope of thestraight-line relationship indicates a change of 48 mV for atenfold change in the ionic strength of the solution. At lowphosphate concentrations the rate of uptake is linearly relatedto the square root of the ionic strength of the solution. Thisis in agreement with the effect of ionic strength on surfacepotential and in turn with the effect of potential on surfaceconcentration of adsorbed ions.