Malleola tibetica sp. nov. (Aeridinae,Orchidaceae) from Tibet,China

Malleola tibetica, a new species from southeastern tropical Tibet, China, is described and illustrated. Morphologically, the new species is closely related to M. dentifera, but differs from it by having uniformly green leaves, flowers with entire lateral lobes of the lip and a basally thickened mid‐lobe, and a column that is densely cristaline‐papillose adaxially.     

Influence of sucrose concentration and phosphate source on biomass and metabolite accumulation in adventitious roots of Pseudostellaria heterophylla

In this study, we investigated the induction of Pseudostellaria heterophylla adventitious root and the effects of sucrose concentration and phosphate source on biomass increase and metabolites accumulation. These roots were initially cultured in Murashige and Skoog medium for 4 weeks. IBA 3.0 mg L^?1 proved to be the best auxin for inducing adventitious roots and the frequency of adventitious roots induced from roots (100 %) was higher than that from leaves (78 %) and stems (27 %). The medium with 4 % sucrose resulted in the optimum biomass i.e. 1.04 g/flask DW, and the content of saponin and polysaccharides reached the peak i.e. 0.676 and 24.4 %, respectively. With regards to phosphate source, 1.25 mM phosphate concentration was more favorable for biomass of roots (0.87 g/flask of DW), whereas the optimum saponin (0.74 %) and polysaccharides (22.09 %) were achieved with 2.5 mM phosphate. However, the saponin content at 2.5 mM phosphate did not show significant difference from the saponin content at 0.625 mM (0.69 %) or 3.75 mM phosphate (0.69 %).     

Characterization of five CIPK genes expressions in maize under water stress

ABA, H₂O₂ and Ca²⁺ play critical roles as signals in the adaptive responses of plants to water and other stresses. They accumulate in plant cells under water and other stresses and induce changes in stress-related gene expressions. CIPKs, protein kinases associated with a calcineurin B-like calcium sensor, play a role in the regulation of stress gene expression in plants. However, it is still unclear whether ABA and H₂O₂ are key inducers that regulate the changes in CIPK expressions under water stress. In this study, five stress-inducible CIPKs in maize were retrieved from Database. They were designated as ZmCIPK1, 3, 8, 17 and 18, based on their homologies with known CIPK sequences. The expressions of the five ZmCIPKs in maize leaves and roots were analyzed and found to be regulated by PEG, CaCl₂, ABA and H₂O₂ to different extents. Moreover, the effect of ABA and H₂O₂ on the expressions of ZmCIPKs under water stress was in an organ-dependent manner.     

Myosin-cross-reactive antigens from four different lactic acid bacteria are fatty acid hydratases

The 67 kDa myosin-cross-reactive antigen (MCRA) is a member of the MCRA family of proteins present in a wide range of bacteria and was predicted to have fatty acid isomerase function. We have now characterised the catalytic activity of MCRAs from four LAB stains, including Lactobacillus rhamnosus LGG, L. plantarum ST-III, L. acidophilus NCFM and Bifidobacterium animalis subsp. lactis BB-12. MCRA genes from these strains were cloned and expressed in Escherichia coli, and the recombinant protein function was analysed with lipid profiles by GC–MS. The four MCRAs catalysed the conversion of linoleic acid and oleic acid to their respective 10-hydroxy derivatives, which suggests that MCRA proteins catalyse the first step in conjugated linoleic acid production. This is the first report of MCRA from L. rhamnosus with such catalytic function.     

Rubia austrozhejiangensis sp. nov. (Rubiaceae) from Zhejiang,China

Rubia austrozhejiangensis Z. P. Lei, Y. Y. Zhou & R. W. Wang, a new species of Rubiaceae from China, is described and illustrated. The new species is similar to R. ovatifolia Z. Ying Zhang and R. argyi (H. Lév. & Vaniot) H. Hara ex Lauener, but differs from the former in having stems and branches cylindrical, not quadrate‐angled, long‐ovate to ovate‐lanceolate leaf blades, many‐flowered inflorescence, and smaller mericarps, 3–4 mm in diameter. In R. ovatifolia, stems and branches are quadrate‐angled, leaf blades ovate, ovate‐cordate to rounded cordate, and the inflorescences are sparsely flowered. Compared to R. argyi, the new species has cylindrical, not quadrate‐angled stems and branches, leaf blades that are long‐ovate to ovate‐lanceolate, 3–5‐veined, and slightly reflexed corolla lobes. In R. argyi, stems and branches are quadrate‐angled or winged, the corolla lobes are spreading, and the mericarps are 5–7 mm in diameter.     

CmPEX6, a Gene Involved in Peroxisome Biogenesis,Is Essential for Parasitism and Conidiation by the Sclerotial Parasite Coniothyrium minitans

Coniothyrium minitans is a sclerotial parasite of the plant-pathogenic fungus Sclerotinia sclerotiorum, and conidial production and parasitism are two important aspects for commercialization of this biological control agent. To understand the mechanism of conidiation and parasitism at the molecular level, we constructed a transfer DNA (tDNA) insertional library with the wild-type strain ZS-1. A conidiation-deficient mutant, ZS-1TN22803, was uncovered through screening of this library. This mutant could produce pycnidia on potato dextrose agar (PDA), but most were immature and did not bear conidia. Moreover, this mutant lost the ability to parasitize or rot the sclerotia of S. sclerotiorum. Analysis of the tDNA flanking sequences revealed that a peroxisome biogenesis factor 6 (PEX6) homolog of Saccharomyces cerevisiae, named CmPEX6, was disrupted by the tDNA insertion in this mutant. Targeted gene replacement and gene complementation tests confirmed that a null mutation of CmPEX6 was responsible for the phenotype of ZS-1TN22803. Further analysis showed that both ZS-1TN22803 and the targeted replacement mutants could not grow on PDA medium containing oleic acid, and they produced much less nitric oxide (NO) and hydrogen peroxide (H₂O₂) than wild-type strain ZS-1. The conidiation of ZS-1TN22803 was partially restored by adding acetyl-CoA or glyoxylic acid to the growth media. Our results suggest that fatty acid β-oxidation, reactive oxygen and nitrogen species, and possibly other unknown pathways in peroxisomes are involved in conidiation and parasitism by C. minitans.     

Characterization of store-operated Ca channels in pancreatic duct epithelia

Store-operated Ca²⁺ channels (SOCs) are activated by depletion of intracellular Ca²⁺ stores following agonist-mediated Ca²⁺ release. Previously we demonstrated that Ca²⁺ influx through SOCs elicits exocytosis efficiently in pancreatic duct epithelial cells (PDEC). Here we describe the biophysical, pharmacological, and molecular properties of the duct epithelial SOCs using Ca²⁺ imaging, whole-cell patch-clamp, and molecular biology. In PDEC, agonists of purinergic, muscarinic, and adrenergic receptors coupled to phospholipase C activated SOC-mediated Ca²⁺ influx as Ca²⁺ was released from intracellular stores. Direct measurement of [Ca²⁺] in the ER showed that SOCs greatly slowed depletion of the ER. Using IP₃ or thapsigargin in the patch pipette elicited inwardly rectifying SOC currents. The currents increased ∼8-fold after removal of extracellular divalent cations, suggesting competitive permeation between mono- and divalent cations. The current was completely blocked by high doses of La³⁺ and 2-aminoethoxydiphenyl borate (2-APB) but only partially depressed by SKF-96365. In polarized PDEC, SOCs were localized specifically to the basolateral membrane. RT-PCR screening revealed the expression of both STIM and Orai proteins for the formation of SOCs in PDEC. By expression of fluorescent STIM1 and Orai1 proteins in PDEC, we confirmed that colocalization of the two proteins increases after store depletion. In conclusion, basolateral Ca²⁺ entry through SOCs fills internal Ca²⁺ stores depleted by external stimuli and will facilitate cellular processes dependent on cytoplasmic Ca²⁺ such as salt and mucin secretion from the exocrine pancreatic ducts.     

Altitudinal Distribution of Ammonia-Oxidizing Archaea and Bacteria in Alpine Grassland Soils Along the South-Facing Slope of Nyqentangula Mountains,Central Tibetan Plateau

Nitrogen is a major limiting nutrient for the net primary production of terrestrial ecosystems, especially on sentinel alpine ecosystem. Ammonia oxidation is the first and rate-limiting step on nitrification process and is thus crucial to nitrogen cycle. To decipher climatic influence on ammonia oxidizers, their communities were characterized by qPCR and clone sequencing by targeting amoA genes (encoding the alpha subunit of ammonia mono-oxygenase) in soils from 7 sites over an 800 m elevation transect (4400–5200 m a.s.l.), based on “space-to-time substitution” strategy, on a steppe-meadow ecosystem located on the central Tibetan Plateau (TP). Archaeal amoA abundance outnumbered bacterial amoA abundance at lower altitude (<4800 m a.s.l.), but bacterial amoA abundance was greater in surface soils at higher altitude (≥4800 m a.s.l.). Archaeal amoA abundance decreased with altitude in surface soil, while its abundance stayed relatively stable and was mostly greater than bacterial amoA abundance in subsurface soils. Conversely, bacterial amoA abundance gradually increased with altitude at all three soil depths. Statistical analysis indicated that altitude-dependent factors, in particular pH and precipitation, had a profound effect on the abundance and community of ammonia-oxidizing bacteria, but only on the community composition of ammonia-oxidizing archaea along the altitudinal gradient. These findings imply that the shifts in the relative abundance and/or community structure of ammonia-oxidizing bacteria and archaea may result from the precipitation variation along the altitudinal gradient. Thus, we speculate that altitude-related factors (mainly precipitation variation combing changed pH), would play a vital role in affecting nitrification process on this alpine grassland ecosystem located at semi-arid area on TP.     

Effects of Hypomagnetic Field on Magnetosome Formation of Magnetospirillum Magneticum AMB-1

Magnetotactic bacteria synthesize intracellular magnetic particles, magnetosomes, which arrange in chain(s) and confer on cell a magnetic dipolar moment. To explore the function of geomagnetic field to magnetotactic bacteria, the effects of hypomagnetic field on magnetosome formation in Magnetospirillum magneticum AMB-1 were studied. Cells were cultivated in a specially designed device where geomagnetic field was reduced by about 100-fold to less than 500nT. AMB-1 cultures were incubated in hypomagnetic field or geomagnetic field. Results showed that hypomagnetic field had no significant effects on the average number of magnetic particles per bacterium and bacterial iron depletion. However, the growth (OD) of cell at stationary-phase was lower and cellular magnetism (R _mag) at exponential growth phase was higher than that of bacteria cultivated in geomagnetic field. Statistic results on transmission electron microscopy (TEM) micrographs showed that the average size of magnetic particles in AMB-1 cells in hypomagnetic field group was larger than that of in geomagnetic field group and more ratio of larger-size magnetic particles (>50 nm) was observed when cultivated 16 h under hypomagnetic field. Furthermore, the influences of hypomagnetic field on gene expression were studied in AMB-1 cells. Quantitative RT-PCR results showed that hypomagnetic field up-regulated mms13, down-regulated mms6 and had no effect on magA. Together, the results showed that hypomagnetic field could affect the growth of AMB-1 at the stationary-phase, the crystallization process of magnetosomes, and mms13, mms6 expressions. In addition, our results suggested that the geomagnetic field plays an important role in the biomineralization of magnetosomes.