GA3和IAA对慈竹综纤维和叶绿素含量动态积累的调控效应

以慈竹为材料,研究不同浓度和配比的GA₃和IAA对综纤维和叶绿素含量动态积累的调控效应,为纸浆用竹的遗传改良研究提供理论依据。研究结果表明, GA₃和IAA处理对慈竹综纤维动态积累调控作用具有差异。处理前30 d内,GA₃50IAA200处理慈竹综纤维积累强度高于GA₃200IAA50处理,40~50 d时,则反之。GA₃和IAA处理的综纤维最终水平明显高于空白对照,差异达极显著水平。GA₃和IAA处理能提高慈竹叶绿素含量,GA₃200IAA50处理慈竹叶绿素含量高于GA₃50IAA200处理。相关分析结果表明,叶绿素含量与综纤维含量间呈不显著正相关关系。     

Roles of leaf in regulation of root and shoot growth from single node softwood cuttings of grape (Vitis vinifera)

The role of leaf in regulation of root and shoot growths in single node softwood cuttings of grape (Vitis vinifera) was characterised. Leafy cuttings showed early rooting, vigorous root growth and subsequent shoot development. Defoliation at planting induced early sprouting, but adversely affected rooting and decreased the survival of cuttings irrespective of pre‐planting treatment with 100 μM indole 3‐acetic acid (IAA). Treatment with IAA did not affect the percent rooting of leafy cuttings but increased root and shoot growth. Leaf weight (wt) and leaf area of the cuttings showed a highly significant correlation to root wt of the new plant at 4 wk after planting, while cutting stem + petiole wt was either not or less significantly correlated to root and shoot weights of the subsequent plant. The greater the area or wt of leaf, the better the root and shoot growths, implying that leaf contributed to adventitious root growth. However, retaining the leaf for just 2 days was enough to stimulate rooting in more than 80% of the cuttings, suggesting that leaf tissue could also induce root formation. Root growth increased with the period of leaf retention but leaf removal before 3 wk triggered sprouting leading to high mortality in rooted cuttings. Bringing the leaf closer to the rooting zone by preparing leaf at base (LAB) cuttings delayed rooting and sprouting compared with the standard leaf at top (LAT) cuttings. An inhibitory effect on rooting and sprouting by the exposed upper internode region in LAB cuttings is suggested.     

Turnover of cell wall components during internode growth in <Emphasis Type="Italic">Merremia emarginata</Emphasis>

The internodes of Merremia emarginata plant showed exceptionally high stretchability throughout the development period. Therefore, it provides excellent material to study the changes undergoing during cell elongation. In this study, the influence of the hormone treatments (GA₃, PAA and NAA) on the wall component synthesis was analyzed in relation to elongation growth during internode development. A clear increasing trend of wall components was observed with increase in internode length. The non-esterified pectic substances were markedly correlated with internode length while esterified pectic substances showed correlation only in hormone treated internodes. Low molecular weight xyloglucans content showed correlation only in GA₃ and NAA treated internodes, while high molecular weight xyloglucans were significantly correlated with length of internodes treated with PAA and NAA.     

生长素信号转导研究进展

长素的信号转导是一个复杂的网络系统,在信号的感知上,除了存在ABPI介导的膜上感知途径外,还有其他的感知途径。G蛋白参与诱导生长素信号的胞内传递,生长素信号转导的第二信使包括离子型第二信使、磷酯酶A2、脂活化蛋白激酶、MAPK和PINOIND等。AUX／IAA蛋白的泛素化降解在生长素反应中发挥关键性作用,ARF和AUX／IAA蛋白相互作用调节生长素响应基因的转录。     

杜仲形成层休眠机理

对杜仲 (EucommiaulmoidesOliv .)一年生枝条休眠中的芽和维管形成层的结构和蛋白质含量进行了研究 ,探讨了杜仲不同休眠期转化的生理生化机理。结果证实了杜仲树的休眠期包括 2个被动休眠期和一个生理休眠期。在生理休眠期 ,无论用外源IAA处理 ,还是给予适当的温度和光照 ,形成层都不能恢复活动。而且 ,雌株进入各个休眠阶段的时间都比雄株早。树皮中的蛋白质含量在第一被动休眠期间 (Q1)显著地逐步增高 (P <0 .0 1) ,进入生理休眠期 (R)后 ,急剧降低 ,但第二被动休眠期 (Q2 )开始后又显著升高 (P <0 .0 1)。杜仲雌雄株树皮中的蛋白质含量变化趋势基本一致 ,但雄株发生变化的时间比雌株早。SDS_PAGE电泳结果表明 ,在Q1 R Q2的转变期出现一11.8kD的特异蛋白条带。此特异蛋白条带可能与形成层休眠期中各阶段的转变调节有关。     

Indicain, a dimeric serine protease from Morus indica cv. K2

A high molecular mass serine protease has been purified to homogeneity from the latex of Morus indica cv. K2 by the combination of techniques of ammonium sulfate precipitation, hydrophobic interaction chromatography, and size-exclusion chromatography. The protein is a dimer with a molecular mass of 134.5 kDa and with two monomeric subunits of 67.2 kDa and 67.3 (MALDI-TOF), held by weak bonds susceptible to disruption on exposure to heat and very low pH. Isoelectric point of the enzyme is pH 4.8. The pH and temperature optima for caseinolytic activity were 8.5 and 80 degrees C, respectively. The extinction coefficient (epsilon280(1%)) of the enzyme was estimated as 41.24 and the molecular structure consists of 52 tryptophan, 198 tyrosine and 42 cysteine residues. The enzyme activity was inhibited by phenylmethylsulfonylflouride, chymostatin and mercuric chloride indicating the enzyme to be a serine protease. The enzyme is fairly stable and similar to subtilases in its stability toward pH, strong denaturants, temperature, and organic solvents. Polyclonal antibodies specific to enzyme and immunodiffusion studies reveal that the enzyme has unique antigenic determinants. The enzyme has activity towards broad range of substrates comparable to those of subtilisin like proteases. The N-terminal residues of indicain (T-T-N-S-W-D-F-I-G-F-P) exhibited considerable similarity to those of other known plant subtilases, especially with cucumisin, a well-characterized plant subtilase. This is the first report of purification and characterization of a subtilisin like dimeric serine protease from the latex of M. indica cv. K2. Owing to these unique properties the reported enzyme would find applications in food and pharma industry.     

The role of activated charcoal in plant tissue culture

Activated charcoal has a very fine network of pores with large inner surface area on which many substances can be adsorbed. Activated charcoal is often used in tissue culture to improve cell growth and development. It plays a critical role in micropropagation, orchid seed germination, somatic embryogenesis, anther culture, synthetic seed production, protoplast culture, rooting, stem elongation, bulb formation etc. The promotary effects of AC on morphogenesis may be mainly due to its irreversible adsorption of inhibitory compounds in the culture medium and substancially decreasing the toxic metabolites, phenolic exudation and brown exudate accumulation. In addition to this activated charcoal is involved in a number of stimulatory and inhibitory activities including the release of substances naturally present in AC which promote growth, alteration and darkening of culture media, and adsorption of vitamins, metal ions and plant growth regulators, including abscisic acid and gaseous ethylene. The effect of AC on growth regulator uptake is still unclear but some workers believe that AC may gradually release certain adsorbed products, such as nutrients and growth regulators which become available to plants. This review focuses on the various roles of activated charcoal in plant tissue culture and the recent developments in this area.     

Introduction of a novel pathway for IAA biosynthesis to rhizobia alters vetch root nodule development

We introduced into Rhizobium leguminosarum bv. viciae LPR1105 a new pathway for the biosynthesis of the auxin, indole-3-acetic acid (IAA), under the control of a stationary phase-activated promoter active both in free-living bacteria and bacteroids. The newly introduced genes are the iaaM gene from Pseudomonas savastanoi and the tms2 gene from Agrobacterium tumefaciens. Free-living bacteria harbouring the promoter-iaaMtms2 construct release into the growth medium 14-fold more IAA than the wild-type parental strain. This IAA overproducing R. l. viciae, the RD20 strain, elicits the development of vetch root nodules containing up to 60-fold more IAA than nodules infected by the wild-type strain LPR1105. Vetch root nodules derived from RD20 are fewer in number per plant, heavier in terms of dry weight and show an enlarged and more active meristem. A significant increase in acetylene reduction activity was measured in nodules elicited in vetch by RD20.