利用数码相机和Photoshop软件非破坏性测定叶面积的简便方法

采用数码相机获取叶片的数字图像,用Photoshop图像处理软件计算叶面积,并与目前常用的剪纸法和叶面积仪测定法进行比较分析。结果表明,本方法和上述传统测定方法测定结果存在极显著线性相关;不同拍摄分辨率、单位叶面积存贮像素个数和拍摄角度对测定结果无显著影响。和其它方法相比,本方法具有准确、快速、成本低廉、适合非破坏性动态连续观测等优点,适用于植物生理生态学研究中叶面积的测定。     

胡杨、灰叶胡杨果实空间分布及其数量特性的研究

胡杨、灰叶胡杨种间比较,果穗、种子在树冠上的垂直分布均表现为树冠上层最多,中层居中,下层最少,树冠南北侧相比较,南侧果穗量多于北侧.单果种子量在树冠各层次上差异不显著.胡杨单果重是灰叶胡杨的2.68倍,千粒重是灰叶胡杨的1.33倍,单果种子量是灰叶胡杨的2.14倍,单株种子量是灰叶胡杨的1.28倍,而单株果实量灰叶胡杨是胡杨的1.59倍.同一个种不同居群间比较,胡杨、灰叶胡杨均是单株果穗数和果穗果实数各居群间都存在差异,胡杨各居群间单果重、单果种子量差异不显著,而灰叶胡杨各居群间单果重及单果种子量差异极显著.表明胡杨在物质和能量上对后代的投资能力强于灰叶胡杨,生殖策略是通过较高的单果种子量来保证一定数量的单株种子量;而灰叶胡杨单果种子量较低,却是通过较高的单株果量来保证单株种子量,并且较小的种子占据空间生态位的潜能较胡杨占优势.     

LT（K63／R72）, a New Mutant of Escherichia coli Heat-labile Enterotoxin, Exhibits Characteristics More Similar to LT（K63） than LT（R72）

LT(K63), a non-toxic mutant and LT(R72), a low toxic mutant of E. coli heat-labile enterotoxin are frequently used mucosal adjuvants. In many cases, the adjuvanticity of LT(K63) is lower than that of LT(R72), but LT(K63), which induces a mixed Th1/Th2 response, exhibits a higher level of protection than LT(R72) which induces a polarized Th2-type response. To utilize the advantages of both adjuvants, a doublemutation LT(K63/R72) was generated and purified. The characterization results showed that there was no significant difference in production rate and immunogenicity between wild type LT and LT mutants. The results also showed that the toxicity and the trypsin sensitivity of LT(K63/R72) are between that of LT(K63)and LT(R72). Using HPLC, when samples in an OHpak SB-800 column were eluted by denatural buffer(TEAN containing 10 mg/ml SDS), we found the stability of LT(K63/R72) was higher than that of LT(R72)and lower than that of LT(K63). Through further analyzes, we found that LT(K63/R72) exhibits characteristics more closely related to LT(K63) than LT(R72).     

Positive Charges on Lysine Residues of the Extrinsic 18 kDa Protein Are Important to Its Electrostatic Interaction with Spinach Photosystem Ⅱ Membranes

To determine the contribution of charged amino acids to binding with the photosystem II complex （PSII）, the amino or carboxyl groups of the extrinsic 18 kDa protein were modified with N- succinimidyl propionate （NSP） or glycine methyl ester （GME） in the presence of a water-soluble carbodiimide, respectively. Based on isoelectric point shift, 4-10 and 10-14 amino groups were modified in the presence of 2 and 4 mM NSP, respectively. Similarly, 3-4 carboxyl groups were modified by reaction with 100 mM GME. Neutralization of negatively charged carboxyl groups with GME did not alter the binding activity of the extrinsic 18 kDa protein. However, the NSP-modified 18 kDa protein, in which the positively charged amino groups had been modified to uncharged methyl esters, failed to bind with the PSII membrane in the presence of the extrinsic 23 kDa protein. This defect can not be attributed to structural or conformational alterations imposed by chemical modification, as the fluorescence and circular dichroism spectra among native, GME- and NSP-modified extrinsic 18 kDa proteins were similar. Thus, we have concluded that the positive charges of lysyl residues in the extrinsic 18 kDa protein are important for its interaction with PSII membranes in the presence of the extrinsic 23 kDa protein. Furthermore, it was found that the negative charges of carboxyl groups of this protein did not participate in binding with the extrinsic 23 kDa protein associated with PSII membranes.     

A thiol-inducible and quick-response DNA cross-linking agent

Three new 2,4-dinitrobenzenesulfonyl derivatives 1–3 were successfully prepared for the first time using a simple process. They were efficiently triggered by thiols (glutathione and l-cysteine) to release the corresponding phenol derivatives (4–6) within 5?min. The quick response of 1–3 toward thiols was determined by ¹H NMR and HPLC. Moreover, our results indicated that 1 could induce DNA cross-linking in the presence of glutathione, probably due to the quinone methide formation of phenol intermediate 4 followed by departure of 2,4-dinitrobenzenesulfonyl group.     

Discovery of 4′-OH-flurbiprofen Mannich base derivatives as potential Alzheimer’s disease treatment with multiple inhibitory activities

A series of 4′-OH flurbiprofen Mannich base derivatives were designed, synthesized and evaluated as potential multifunctional agents for the treatment of Alzheimer’s disease. The biological screening results indicated that most of these derivatives exhibited good multifunctional activities. Among them, compound 8n demonstrated the best inhibitory effects on self-induced Aβ_1-42 aggregation (65.03% at 25.0?μM). Moreover, this representative compound also exhibited good antioxidant activity, biometal chelating ability and anti-neuroinflammatory activity in vitro. Furthermore, compound 8n displayed appropriate blood-brain barrier permeability. These multifunctional properties highlight compound 8n as promising candidate for further development of multi-functional drugs against AD.     

The histone demethylase Jmjd3 regulates zebrafish myeloid development by promoting spi1 expression

The histone demethylase Jmjd3 plays a critical role in cell lineage specification and differentiation at various stages of development. However, its function during normal myeloid development remains poorly understood. Here, we carried out a systematic in vivo screen of epigenetic factors for their function in hematopoiesis and identified Jmjd3 as a new epigenetic factor that regulates myelopoiesis in zebrafish. We demonstrated that jmjd3 was essential for zebrafish primitive and definitive myelopoiesis, knockdown of jmjd3 suppressed the myeloid commitment and enhanced the erythroid commitment. Only overexpression of spi1 but not the other myeloid regulators rescued the myeloid development in jmjd3 morphants. Furthermore, preliminary mechanistic studies demonstrated that Jmjd3 could directly bind to the spi1 regulatory region to alleviate the repressive H3K27me3 modification and activate spi1 expression. Thus, our studies highlight that Jmjd3 is indispensable for early zebrafish myeloid development by promoting spi1 expression.     

Linkage and association mapping reveals the genetic basis of brown fibre (Gossypium hirsutum)

Brown fibre cotton is an environmental‐friendly resource that plays a key role in the textile industry. However, the fibre quality and yield of natural brown cotton are poor, and fundamental research on brown cotton is relatively scarce. To understand the genetic basis of brown fibre cotton, we constructed linkage and association populations to systematically examine brown fibre accessions. We fine‐mapped the brown fibre region, Lc₁, and dissected it into 2 loci, qBF‐A07‐1 and qBF‐A07‐2. The qBF‐A07‐1 locus mediates the initiation of brown fibre production, whereas the shade of the brown fibre is affected by the interaction between qBF‐A07‐1 and qBF‐A07‐2. Gh_A07G2341 and Gh_A07G0100 were identified as candidate genes for qBF‐A07‐1 and qBF‐A07‐2, respectively. Haploid analysis of the signals significantly associated with these two loci showed that most tetraploid modern brown cotton accessions exhibit the introgression signature of Gossypium barbadense. We identified 10 quantitative trait loci (QTLs) for fibre yield and 19 QTLs for fibre quality through a genome‐wide association study (GWAS) and found that qBF‐A07‐2 negatively affects fibre yield and quality through an epistatic interaction with qBF‐A07‐1. This study sheds light on the genetics of fibre colour and lint‐related traits in brown fibre cotton, which will guide the elite cultivars breeding of brown fibre cotton.