Midday depression of photosynthesis in <Emphasis Type="Italic">Enkleia malaccensis</Emphasis>, a woody climber in a tropical rainforest

We measured the diurnal changes in net photosynthetic rate (P _N) and stomatal conductance (g _s) of the leaves of a liana, Enkleia malaccensis Griff. (Thymelaeaceae), at the canopy level in the lowland tropical rainforest at Pasoh, Peninsular Malaysia. The measurements were made from a canopy walkway system, 30 m from the ground for 3 d in March 2003. P _N increased with increasing photosynthetically active radiation (PAR) before noon, though P _N was not enhanced by the strong radiation hit in the afternoon. Plotting g _s at saturating PAR (>0.5 mmol m⁻² s⁻¹) against the vapour pressure deficit (VPD) failed to reveal a significant correlation between VPD and g _s, and g _s became very low at VPD >2.5 kPa. The relationship between P _N and g _s was fitted on the same regression line irrespective of measuring day, indicating that this relationship was not influenced by either VPD or leaf temperature (T _L). Therefore, in the liana E. malaccensis, an increase in VPD leads to partial stomatal closure and, subsequently, reductions in P _N and the midday depression of P _N of this plant.     

Optimization of particle bombardment parameters for DNA delivery into the male flowers of banana

The possibility of increasing the efficiency of banana transformation was investigated by particle bombardment of the male flowers of banana plants for constitutive expression of gfp gene. The effects of particle bombardment parameters, such as acceleration pressure, bombardment distance, chamber vacuum pressure, gold microcarrier size, gold quantity, DNA quantity, number of bombardments and pre-culture were examined. Single cauliflower-like bodies (CLBs) clusters, induced from meristemic parts of Musa sapientum cv. Nangka (AAB) male flowers, were bombarded by pCambia1304 plasmid carrying gfp gene driven by the CaMV 35S promoter. Optimal transient expression of green-fluorescent protein (GFP) was obtained when the three-day old cultured tissues were bombarded two times at 1100 psi helium pressure. However, the highest GFP expression was observed when 9 cm was applied as bombardment distance with 28 mmHg chamber vacuum pressure. Gold particle with 1 μm diameter at 60 μg/μL concentrations coated with 1.5 μg/μL of DNA have been used as the optimum bombardment parameter since GFP expression was significantly different compared to other conditions. Application of optimized condition proved effective for the generation of stable transgenic banana plants. PCR and southern blot analyses confirmed the presence and integration of gfp gene in genomic DNA of transformed plants. Transformation frequency achieved with the optimized protocol was 7.5% which was significantly higher than the conventional protocol.     

Overexpressing 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase (HMGR) in the Lactococcal Mevalonate Pathway for Heterologous Plant Sesquiterpene Production

Isoprenoids are a large and diverse group of metabolites with interesting properties such as flavour, fragrance and therapeutic properties. They are produced via two pathways, the mevalonate pathway or the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway. While plants are the richest source of isoprenoids, they are not the most efficient producers. Escherichia coli and yeasts have been extensively studied as heterologous hosts for plant isoprenoids production. In the current study, we describe the usage of the food grade Lactococcus lactis as a potential heterologous host for the production of sesquiterpenes from a local herbaceous Malaysian plant, Persicaria minor (synonym Polygonum minus). A sesquiterpene synthase gene from P. minor was successfully cloned and expressed in L. lactis. The expressed protein was identified to be a β-sesquiphellandrene synthase as it was demonstrated to be functional in producing β-sesquiphellandrene at 85.4% of the total sesquiterpenes produced based on in vitro enzymatic assays. The recombinant L. lactis strain developed in this study was also capable of producing β-sesquiphellandrene in vivo without exogenous substrates supplementation. In addition, overexpression of the strain’s endogenous 3-hydroxy-3-methylglutaryl coenzyme-A reductase (HMGR), an established rate-limiting enzyme in the eukaryotic mevalonate pathway, increased the production level of β-sesquiphellandrene by 1.25–1.60 fold. The highest amount achieved was 33 nM at 2 h post-induction.     

Spectaflavoside A, a new potent iron chelating dimeric flavonol glycoside from the rhizomes of Zingiber spectabile Griff

The rhizomes of Zingiber spectabile yielded a new dimeric flavonol glycoside for which the name kaempferol-3-O-(4″-O-acetyl)-α-L-rhamnopyranoside-(I-6,II-8)-kaempferol-3-O-(4″-O-acetyl)-α-L-rhamnopyranoside; spectaflavoside A (1) was proposed, along with kaempferol and its four acetylrhamnosides (2-6), demethoxycurcumin (7) and curcumin (8). The structure of spectaflavoside A was elucidated by spectroscopic methods including, 1D and 2D NMR techniques. This is the first report on the occurrence of a dimeric flavonol glycoside in the Zingiberaceae and the second in nature. Spectaflavoside A was found to be a potent iron chelating agent.     

Morphological and phenological characteristics of leaf development ofDurio zibethinus Murray (Bombacaceae)

The morphological and phenological characteristics of leaf development ofDurio zibethinus Murray were investigated at an experimental field of Universiti Pertanian Malaysia (UPM) in Selangor. Proportionality was observed in the relations of leaf length to leaf width and of leaf area to the product of leaf width and length. The proportionality was explained from the similarity of leaf shape. New leaves emerged continuously, but the number of new leaves fluctuated seasonally. The emergence of leaves was inhibited by the flower bud formation. In the survival curves of leaves, the relative fall rate was lower at the early stage of leaf development than at the late stage. Leaf longevity of 100 to 133 days was low and leaf expansion period of two weeks was short in comparison with the published data on tropical trees. From the ecophysiological viewpoint, the leaf survival strategy of the present species was discussed: the present species manages to set up a photosynthetic system in a short period by the rapid leaf growth; the lower leaf longevity is advantageous to reaching more frequently high photosynthetic production by newly emerged leaves.     

The effect of fermentable carbohydrate on sporulation and butanol production by Clostridium acetobutylicum P262

Summary This study was conducted to determine whether or not a variation in the type of carbohydrate fermented by Clostridium acetobutylicum could be exploited to inhibit sporulation during the butanol-producing phase of fermentation and thus enhance butanol production. C. acetobutylicum P262 was found to ferment a wide variety of carbohydrates, but butanol production was not necessarily enhanced when percentage sporulation was low. Butanol concentration was more related to the total amount of acidic end-products (acetic and butyric acid) reutilized by the microorganism for solvent production and to the type and amount of carbohydrate utilized. Fermentation of cellobiose led to conditions resulting in complete acid reutilization and the highest butanol concentration (10.4–10.6 g/l). In cultures containing a mixture of glucose and cellobiose, glucose repression of cellobiose utilization resulted in lower butanol concentrations (6.6–7.5 g/l). Sporulation was dependent on the type of carbohydrate utilized by the microorganism. Glucose had a greater enhancing effect on the sporulation process (22–42%) than starch (9–12%) or cellobiose (22–34%). It was concluded that whereas the type of carbohydrate fermented had a specific effect on the extent of sporulation of a culture, conditions of low sporulation did not enhance butanol concentration unless carbohydrate utilization and the reutilization of acidic products were high.Correspondence to: W. M. Ingledew     

Diel changes in the CO2 exchange rates of reproductive organs of the tropical tree Durio zibethinus

The daily variations in the in situ CO₂ exchange of the reproductive organs of Durio zibethinus trees, growing in an experimental field at University Putra Malaysia (UPM), were examined at different growth stages. Reproductive organs emerged on the leafless portions of branches inside the crown. The photon flux densities (PFD) in the chambers used for the measurements were less than 100 mol m^–2 s^–1 and were 40% of the PFD outside of the crown. The daytime net respiration rate and the nighttime dark respiration rate were higher at the time of flower initiation and during the mixed stages, when flower buds, flowers, and fruit coexist, than at the flower bud stage. The net respiration rate was lower than the daytime dark respiration rate at given temperatures, especially at the flower bud and fruit stages. Conversely, the net respiration rate was similar to the daytime dark respiration rate at the mixed stage. Photosynthetic CO₂ refixation reduced the daily respiratory loss by 17, 5, 0.3, and 24% at the flower bud, flower initiation, mixed, and fruit stages, respectively.     

Cycloart-24-ene-26-ol-3-one,a New Cycloartane Isolated from Leaves of Aglaia exima Triggers Tumour Necrosis Factor-Receptor 1-Mediated Caspase-Dependent Apoptosis in Colon Cancer Cell Line

Plants in the Meliaceae family are known to possess interesting biological activities, such as antimalaral, antihypertensive and antitumour activities. Previously, our group reported the plant-derived compound cycloart-24-ene-26-ol-3-one isolated from the hexane extracts of Aglaia exima leaves, which shows cytotoxicity towards various cancer cell lines, in particular, colon cancer cell lines. In this report, we further demonstrate that cycloart-24-ene-26-ol-3-one, from here forth known as cycloartane, reduces the viability of the colon cancer cell lines HT-29 and CaCO-2 in a dose- and time-dependent manner. Further elucidation of the compound’s mechanism showed that it binds to tumour necrosis factor-receptor 1 (TNF-R1) leading to the initiation of caspase-8 and, through the activation of Bid, in the activation of caspase-9. This activity causes a reduction in mitochondrial membrane potential (MMP) and the release of cytochrome-C. The activation of caspase-8 and -9 both act to commit the cancer cells to apoptosis through downstream caspase-3/7 activation, PARP cleavage and the lack of NFkB translocation into the nucleus. A molecular docking study showed that the cycloartane binds to the receptor through a hydrophobic interaction with cysteine-96 and hydrogen bonds with lysine-75 and -132. The results show that further development of the cycloartane as an anti-cancer drug is worthwhile.     

Occurrence of Ralstonia solanacearum Race 2 Biovar 1 Associated with Moko Disease of Banana (Musa paradisiaca cv. Nipah) in Malaysia

During June 2011 to March 2012, Moko disease symptoms were observed in banana cv. Nipah in two Malaysian states. The primer pairs ISRso19F/ISRso19R were used for defined identification of Ralstonia solanacearum race 2 strain. PCR amplification of all isolates produced a 1900 amplicon and exhibited 93% phylogenetic similarity with reference strain (AF450275). Based on symptoms, biochemical tests, pathogenicity assay, molecular and phylogenetic studies, we concluded that the isolated bacterium was R. solanacearum race 2 biovar 1.     

Simple, rapid and sensitive assay method for simultaneous quantification of urinary nicotine and cotinine using gas chromatography-mass spectrometry

Nicotine is a major addictive compound in cigarette. Its smoke is rapidly and extensively metabolized to several metabolites in human. Cotinine as a major metabolite of nicotine is commonly used as a biomarker to determine active and passive smokers. Cotinine has a longer half-life ( approximately 20 h) compared to nicotine ( approximately 2h). A simple, sensitive, rapid and high throughput GC-MS method was developed for simultaneous quantification of urinary nicotine and cotinine in passive and active smokers. In the sample preparation method, the analytes and internal standard were first basified and followed by liquid-liquid extraction. Upon completion, anhydrous sodium sulphate was added to the solvent mixture to trap moistures. The clear extract obtained was directly injected into GC-MS, operating under selective ion monitoring (SIM) mode. Calibration curves in the range of 0.5-5000 ng/mL of the analytes in urine matrix were established with linear correlation coefficients (r(2)) greater than 0.997. The limit of detection for both nicotine and cotinine were 0.20 ng/mL. The mean recoveries for nicotine and cotinine were 93.0 and 100.4%, respectively. The within- and between-assay accuracies were between 2.1 and 7.9% for nicotine and between 0.7 and 11.1% for cotinine. Within- and between-assay precisions of 3.3-9.5% for nicotine and 3.4-9.8% for cotinine were also achieved. The method can be used in routine assessment and monitoring of active smoking and exposure to environmental tobacco smoke. The applicability of the assay was demonstrated in a small-scale comparison study between smokers and non-smokers.