Development and evaluation of Trichoderma asperellum preparation for control of sheath blight of rice (Oryza sativa L.)

Sheath blight, which is caused by Rhizoctonia solani, is a disease that majorly impacts rice production. A biocontrol agent used for control rice sheath blight must be sprayed on the stem at specific times during rice growth, a process that is labour-intensive and renders the antagonist vulnerable to environmental factors. In this study, Trichoderma asperellum T12 was used to produce preparation by solid-state fermentation using a surface-response method. Rice hull was selected as a carrier based on its ability to sustain the T12 floating in the water and protect T12 from ultraviolet irradiation. The production of a T12-based preparation required 32% wheat bran, 7% inoculum, 2.3 g kg^?1 (NH₄)₂SO₄ and 65% water content, with fermentation at 27.5°C for 30 days and agitation every six days. The preparation demonstrated 90% biocontrol efficacy and significantly (P > 0.05) increased the seed-set rate and 1000-grain weight as compared with the pathogen treatment. The population of Trichoderma on the surface of rice leaf sheath in the treatment applied with T12 preparation increased from 232 cfu (colony forming units) g^?1 fw (fresh weight) to 436 cfu g^?1 fw during rice growth stage, which was significantly (P > 0.05) higher than pathogen treatment. The population of R. solani on the leaf sheath increased from 41 cfu g^?1 fw to 271 cfu g^?1 fw in the pathogen treatment, while remained stable (P > 0.05) at level of 10–23 cfu g^?1 fw in T12 preparation applied treatment. Biocontrol of sheath blight by the addition of the preparation to the soil is effective and decreases the costs of agro-industrial waste disposal.     

玉米叶片主脉及其鞘组织的早期发育和超微结构

研究了玉米叶片中层基本分生组织３个相邻细胞形成主脉原形成层及维管束鞘（ＢＳ）的早期发育过程和超微结构。结果表明，在由３个相邻细胞组成的３－细胞单元中，位于中间的细胞发生２次平周分裂，产生１个较小的和１个较大的细胞，前者分化为近轴端ＢＳ细胞前体，后者再发生１次不均等平周分裂产生１个远轴端ＢＳ细胞前体和１个原形成层起始细胞；位于两侧的细胞其中有１个也发生１次平周分裂，所产生的２个子细胞与另１个侧向细胞     

Primary structure of the tail sheath protein of bacteriophage T4 and its gene

Complete sequence determination of gene 18 encoding the tail sheath protein was carried out mainly by the Maxam-Gilbert method. Approximately 40 peptides contained in a tryptic digest and a lysyl endopeptidase digest of gp 18 were isolated by reversed-phase high-performance liquid chromatography. All the peptides were identified along the nucleotide sequence of gene 18 based on the amino acid compositions. These peptides cover 88% of the total primary structure. Furthermore, the amino acid sequences of 9 of the 40 peptides were determined by a gas-phase protein sequencer; one of them turned to be the N-terminal one. The C-terminal peptide in the tryptic digest was isolated from the unadsorbed fraction of affinity chromatography on immobilized anhydrotrypsin and the amino acid sequence was also determined. Thus, the complete primary structure of gp 18 was determined; it has 658 amino acid residues and a molecular weight of 71,160.This article was presented during the proceedings of the International Conference on Macromolecular Structure and Function, held at the National Defence Medical College, Tokorozawa, Japan, December 1985.     

不同海拔地区种植的水稻次库碳水化合物含量的比较

在品种、土壤、底肥和追肥等一致的情况下,对三个不同海拔地区种植的水稻的次库(茎+叶鞘)中碳水化合物含量作了比较,结果表明:齐穗和黄熟期次库中总糖或淀粉含量均随海拔增高而增加。但在黄熟期,高海拔地区次库的总糖或淀粉含量比齐穗期的增加,而低海拔地区次库的总糖或淀粉含量则比齐穗期的降低。 齐穗期时,次库的淀粉含量随施用的氮素肥量的增加而降低。在黄熟期,温凉稻作区水稻次库的淀粉含量均随氮素底肥施用量的增加而增加,低熟地区水稻次库的淀粉含量则趋于一致,不过不同地区相比各处理次库的淀粉含量均因海拔增高而增加。 不同时期的氮素追肥使齐穗期次库淀粉含量因追肥时间推迟而增加,唯元江晚穗肥处理的低于中穗肥处理的。黄熟期因追肥时间提早而次库的淀粉含量增加,但元江以早穗肥处理的次库淀粉含量最低。与齐穗期相比时,低海拔地区的各个处理,其次库的淀粉含量均减低,但高海拔的昆明温凉稻作区,施早和中穗肥的水稻,在黄熟期次库的淀粉含量反而增高。还可以看出水稻种植地海拔越高,其次库淀粉含量对追肥时间越敏感。 基于水稻次库中淀粉含量对氮素肥料的反应,就三地气候条件讨论了上述的差异。     

A Novel Gene Encoding an Enzyme That Degrades a Polysaccharide from the Sheath of Sphaerotilus natans

A gene encoding an enzyme that is able to depolymerize the basic polysaccharide prepared from the sheath of Sphaerotilus natans was identified in a sheath-degrading bacterium, Paenibacillus koleovorans. The gene was constructed from 2217 bp coding for 738 amino acids, including the signal sequence of 34 amino acids. No closely related protein or gene was indicated by a homology search. The gene was expressed in Escherichia coli as a glutathione S-transferase fusion protein. The fusion protein depolymerized the sheath polysaccharide into an oligosaccharide, introducing an unsaturated sugar residue, suggesting that the gene codes for a polysaccharide lyase acting on a basic polysaccharide.     

Upregulation of bundle sheath electron transport capacity under limiting light in C4 Setaria viridis

C₄ photosynthesis is a biochemical pathway that operates across mesophyll and bundle sheath (BS) cells to increase CO₂ concentration at the site of CO₂ fixation. C₄ plants benefit from high irradiance but their efficiency decreases under shade, causing a loss of productivity in crop canopies. We investigated shade acclimation responses of Setaria viridis, a model monocot of NADP-dependent malic enzyme subtype, focussing on cell-specific electron transport capacity. Plants grown under low light (LL) maintained CO₂ assimilation rates similar to high light plants but had an increased chlorophyll and light-harvesting-protein content, predominantly in BS cells. Photosystem II (PSII) protein abundance, oxygen-evolving activity and the PSII/PSI ratio were enhanced in LL BS cells, indicating a higher capacity for linear electron flow. Abundances of PSI, ATP synthase, Cytochrome b₆f and the chloroplast NAD(P)H dehydrogenase complex, which constitute the BS cyclic electron flow machinery, were also increased in LL plants. A decline in PEP carboxylase activity in mesophyll cells and a consequent shortage of reducing power in BS chloroplasts were associated with a more oxidised plastoquinone pool in LL plants and the formation of PSII – light-harvesting complex II supercomplexes with an increased oxygen evolution rate. Our results suggest that the supramolecular composition of PSII in BS cells is adjusted according to the redox state of the plastoquinone pool. This discovery contributes to the understanding of the acclimation of PSII activity in C₄ plants and will support the development of strategies for crop improvement, including the engineering of C₄ photosynthesis into C₃ plants.     

Compartmentation and fluxes of carbon in leaf blades and leaf sheaths of Poa annua L. and Poa x jemtlandica (Almq.) Richt

Abstract The allocation of photosynthetically fixed carbon in the leaf blades and sheaths of Poa annua (a ruderal grass) and Poa x jemtlandica (a sub-arctic grass) was followed over a light-dark cycle. Labelling with ¹⁴Carbon and gas exchange measurements provide data for an eight-compartment model describing the partitioning of carbon between spatially and chemically separated pools and their rates of turnover. Soluble sugars and fructans were turned over rapidly in the leaf blades of both species. The flux of carbon through pools of storage carbohydrates was higher in the leaves of P. x jemtlandica than in P. annua. The exchange of carbon between pools was slower in the sheath than the blade. Carbohydrates stored in the sheath appeared to have no significant role in metabolism over the light-dark cycle studied here.     

PACAP and VIP increase the expression of myelin-related proteins in rat schwannoma cells: Involvement of PAC1/VPAC2 receptor-mediated activation of PI3K/Akt signaling pathways

PACAP and its cognate peptide VIP participate in various biological functions, including myelin maturation and synthesis. However, defining whether these peptides affect peripheral expression of myelin proteins still remains unanswered. To address this issue, we assessed whether PACAP or VIP contribute to regulate the expression of three myelin proteins (MAG, MBP and MPZ, respectively) using the rat schwannoma cell line (RT4-P6D2T), a well-established model to study myelin gene expression. In addition, we endeavored to partly unravel the underlying molecular mechanisms involved. Expression of myelin-specific proteins was assessed in cells grown either in normal serum (10% FBS) or serum starved and treated with or without 100 nM PACAP or VIP. Furthermore, through pharmacological approach using the PACAP/VIP receptor antagonist (PACAP6-38) or specific pathway (MAPK or PI3K) inhibitors we defined the relative contribution of receptors and/or signaling pathways on the expression of myelin proteins. Our data show that serum starvation (24 h) significantly increased both MAG, MBP and MPZ expression. Concurrently, we observed increased expression of endogenous PACAP and related receptors. Treatment with PACAP or VIP further exacerbated starvation-induced expression of myelin markers, suggesting that serum withdrawal might sensitize cells to peptide activity. Stimulation with either peptides increased phosphorylation of Akt at Ser473 residue but had no effect on phosphorylated Erk-1/2. PACAP6-38 (10 μM) impeded starvation- or peptide-induced expression of myelin markers. Similar effects were obtained after pretreatment with the PI3K inhibitor (wortmannin, 10 μM) but not the MAPKK inhibitor (PD98059, 50 μM). Together, the present finding corroborate the hypothesis that PACAP and VIP might contribute to the myelinating process preferentially via the canonical PI3K/Akt signaling pathway, providing the basis for future studies on the role of these peptides in demyelinating diseases.