Species of Pratylenchus Associated with Solanum tuberosum cv Superior in Ohio

Seventy-three Ohio fields comprising ca. 440 ha of cv Superior potatoes were surveyed in 1977 for plant-parasitic nematodes. Of eight genera of plant-parasitic nematodes, Pratylenchus was found most frequently, occurring in 65% of the soil samples and 84% of the root samples. Populations of Pratylenchus were consistently higher than populations of the other nematode genera. The six species of Pratylenchus extracted from potato roots, in descending order of frequency, were P. crenatus, P. penetrans, P. scribneri, P. alleni, P. thornei, and P. neglectus. Prevalence of these Pratylenchus species in Ohio potato fields suggests that they could be involved with vascular wilt fungi in premature death of cv Superior potato vines known in Ohio as "early dying."     

Comparison of Five Populations of Tylenchulus semipenetrans to Citrus,Poncirus, and their Hybrids

The infectivity of five populations of Tylenchulus semipenetrans were compared and differentiated on 10 hosts (5 Citrus spp., 1 Poncirus trifoliata, and 4 hybrids of Citrus spp. X P. trifoliata). Differences in levels of infection and development (P = 0.01) occurred between Citrus spp. and P. trifoliata cv. ''Pomeroy'' and their three hybrids, C. paradisi X P. trifoliata cv. ''Swingle'' citruntelo and C. sinensis, cv. ''Ruby'' orange X P. trifoliata cv. ''Webber Fawcett 14-7'', and ''15-7''. Poncirus trifoliata cv. Pomeroy was susceptible to a California biotype 3 and highly resistant to the other citrus nematode populations. Low infection levels with California biotype 1, Arizona, and Florida populations on Swingle citrumelo, and the two Ruby orange hybrids indicated inherited resistance. Reproduction of the nematode population from Texas was greatest on the three hybrids, Swingle citrumelo, Ruby orange 14-7, and 15-7, from the California 1, Arizona, and Florida populations, but its comparable densities on P. trifoliata and Citrus spp. were not sufficiently different from these populations to consider it a separate biotype. California biotype 3 was sufficiently different from all other populations to be considered a different biotype, and it was named the "Poncirus biotype."     

Long-Term Fungal Inhibitory Activity of Water-Soluble Extracts of Phaseolus vulgaris cv. Pinto and Sourdough Lactic Acid Bacteria during Bread Storage

The antifungal activity of proteinaceous compounds from different food matrices was investigated. In initial experiments, water-soluble extracts of wheat sourdoughs, cheeses, and vegetables were screened by agar diffusion assays with Penicillium roqueforti DPPMAF1 as the indicator fungus. Water-soluble extracts of sourdough fermented with Lactobacillus brevis AM7 and Phaseolus vulgaris cv. Pinto were selected for further study. The crude water-soluble extracts of L. brevis AM7 sourdough and P. vulgaris cv. Pinto had a MIC of 40 mg of peptide/ml and 30.9 mg of protein/ml, respectively. MICs were markedly lower when chemically synthesized peptides or partially purified protein fractions were used. The water-soluble extract of P. vulgaris cv. Pinto showed inhibition toward a large number of fungal species isolated from bakeries. Phaseolin alpha-type precursor, phaseolin, and erythroagglutinating phytohemagglutinin precursor were identified in the water-soluble extract of P. vulgaris cv. Pinto by nano liquid chromatography-electrospray ionization-tandem mass spectrometry. When the antifungal activity was assayed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, all three proteins were inhibitory. A mixture of eight peptides was identified from the water-soluble extract of sourdough L. brevis AM7, and five of these exhibited inhibitory activity. Bread was made at the pilot plant scale by sourdough fermentation with L. brevis AM7 and addition of the water-soluble extract (27%, vol/wt; 5 mg of protein/ml) of P. vulgaris cv. Pinto. Slices of bread packed in polyethylene bags did not show contamination by fungi until at least 21 days of storage at room temperature, a level of protection comparable to that afforded by 0.3% (wt/wt) calcium propionate.     

Interactions between Heterodera avenae and Pratylenchus neglectus on Wheat

In a long-term field experiment, differential population densities of Heterodera avenae were produced by frequent cropping with resistant (cv. Panema) or susceptible (cv. Peniarth) oat. The two oat cultivars were equally good hosts of Pratylenchus neglectus in a glass house experiment with field soil. On wheat crops grown after oats in field experiments, P. neglectus population densities in roots were higher in plots where H. avenae had been controlled than in plots with moderate infestations (40 H. avenae eggs/g soil). The field observations indicated that the reduction in population densities of P. neglectus coincided with the development in roots of sedentary stages of the cyst nematode. Evidence for an indirect effect of H. avenae on P. neglectus was found in vitro in a split-root experiment. In the same field, grain yields of two wheat cultivars susceptible or resistant to H. avenae, but both susceptible to P. neglectus, was not reduced by P. neglectus. Alternation of H. avenae resistant and susceptible cultivars is a possible way of exploiting the inverse relationship between these nematodes, whilst controlling cyst nematode -populations in intensive cereal production systems.     

Population Growth of Pratylenchus penetrans on Winter Cover Crops Grown in the Pacific Northwest

Population growth of Pratylenchus penetrans on 13 fall and winter cover crops was studied in the greenhouse and field. All crops except oat cv. Saia supported population growth of P. penetrans in greenhouse experiments, although the response of P. penetrans to oat cv. Saia varied considerably between experiments. The mean ratio of the final population density/initial population density (Pf/Pi) after 16 weeks for P. penetrans added to a greenhouse soil mix was 0.09, whereas Pf/Pi values after 10 weeks for two experiments with naturally infested soil were 0.95 and 2.3. Although P. penetrans increased on sudangrass cv. Trudan 8 and sudangrass × sorghum hybrid cv. SS 222, subsequent incorporation of sudangrass vegetation into soil reduced P. penetrans populations to preplant levels. Field experiments were inconclusive but suggested that oat cv. Saia or rye cv. Wheeler may be better choices for winter cover than weed-contaminated fallow or other crops on P. penetrans-infested sites in the Pacific Northwest.     

Root Hair Deformation, Bacterial Attachment, and Plant Growth in Wheat-Azospirillum Associations

Seven Azospirillum strains induced more deformation of root hairs of wheat than did strains of Rhizobium leguminosarum, Azotobacter chroococcum, or Escherichia coli. Azospirillum sp. strain Sp245 caused the most deformation. Strain Sp245 (isolated from surface sterile roots of wheat) and strain Sp7 (isolated from the rhizosphere of a forage grass) were compared with regard to their effects on root hair deformation, their attachment to roots, and their effects on the growth of four wheat cultivars. The amount of deformation caused by the two strains in the four cultivars increased in the following order: cv. Tobari, cv. Tonari, cv. BH1146, cv. Lagoa. Strain Sp245 attached to the roots of all cultivars in low numbers, and attachment did not increase with time (up to 48 h). Strain Sp7 attached in higher numbers, and attachment increased with time. Inoculation of the four cultivars of wheat had pronounced effects on root mass measured at maturity. The magnitude of the effects in the four cultivars increased in the following order: Tobari, Tonari, BH1146, Lagoa; these effects were progressively more positive for strain Sp245 and progressively more negative for strain Sp7. Concentrations of N in wheat did not vary substantially between cultivars or strains. Concentrations of K and P did not vary substantially between cultivars but did vary between strains, Sp245 effecting increases and Sp7 effecting decreases.     

两种栽培型广藿香内生真菌群落组成变化

为探索内生真菌与广藿香互作间对宿主活性成分形成机制的影响,该研究以成分差异较大的牌香和湛香为对象,采用传统形态学方法对所获菌株归类,通过真菌通用引物ITS1/ITS4扩增菌株rDNA-ITS序列,鉴定其分类地位并研究其多样性。结果表明：(1)用PDA和LBA培养基对苗期、分枝期和成株期广藿香茎叶组织块进行内生真菌分离,共获得3 070株菌株,其中牌香(PX)分离出1 624株,鉴定出1 319株,分属于36属;湛香(ZX)分离出1 446株,鉴定出994株,分属于33属。牌香分离出7种特有内生真菌,分别为香柱菌(Epichloe typhina)、盘长孢状刺盘孢菌(Colletotrichum gloeosporioides)、座腔孢菌(Botryosphaeria sp.)、丝核菌(Rhizoctonia sp.)及截盘多毛孢菌(Truncatella sp.),并首次分离到疫霉菌(Phytophthora sp.)和指疫霉菌(Sclerophthora sp.),这2种菌属于卵菌门内生菌。湛香分离出拟青霉菌(Paecilomyces sp.)和尾孢菌(Cercospora sp.)...     

Suppression of Alfalfa Growth by Concommitant Populations of Pratylenchus penetrans and two Fusarium species

Growth of alfalfa (Medicago sativa cv. Vernal) seedlings was compared after inoculation with combinations of either Pratylenchus penetrans and Fusarium soloni or P. penetrans and F. oxysporum f. sp. medicaginis. A synergistic disease interaction occurred in alfalfa when F. oxysporum and P. penetrans were added simultaneously to the soil. Alfalfa growth was suppressed at all inoculum levels of P. penetrans and F. oxysporum, but not with F. solani. Seedlings inoculated with the nematode alone gave lower yields than when inoculated with either Fusarium species alone. Fusarium oxysporum, but not F. solani, was pathogenic to alfalfa under similar experimental conditions. Fusarium oxysporum did not alter the populations of P. penetrans in alfalfa roots, whereas the presence of F. solani was associated with a diminished number of P. penetrans in the roots.     

The metacaspase gene family of Vitis vinifera L.: Characterization and differential expression during ovule abortion in stenospermocarpic seedless grapes

In both plants and animals, programmed cell death (PCD) is an indispensable process that removes redundant cells. In seedless grapes (Vitis vinifera), abnormal PCD in ovule cells and subsequent ovule abortion play key roles in stenospermocarpy. Metacaspase, a type of cysteine-dependent protease, plays an essential role in PCD. To reveal the characteristics of the metacaspase (MC) gene family and the relationship between metacaspases and the seedless trait, we identified the 6 V. vinifera metacaspases VvMC1–VvMC6, from the grape genome, using BLASTN against the 9 known Arabidopsis metacaspases. We also obtained full-length cDNAs by RT-PCR. Each of the 6 grape metacaspases contains small (p10-like) and a large (p20-like) conserved structural domains. Phylogenetic analysis of 6 grape and 9 Arabidopsis metacaspases showed that all metacaspases could be grouped into two classes: Type I and Type II. Each phylogenetic branch shares a similar exon/intron structure. Furthermore, the putative promoters of the grape metacaspases contained cis-elements that are involved in grape endosperm development. Moreover, expression analysis of metacaspases using real-time quantitative PCR demonstrated that VvMC1 and VvMC2 were able to be detected in any tissue, and VvMC3, VvMC4, VvMC5 and VvMC6 exhibited tissue-specific expression. Lastly, in cv. Thompson seedless grapes VvMC1, VvMC3, and VvMC4 were significantly up-regulated at the 35 DAF during ovule development, roughly same stage as endosperm abortion. In addition, the expression trend of VvMC2 and VvMC5 was similar between cv. Pinot Noir and cv. Thompson grape ovule development and that of VvMC6 was sustained in a relatively low level except the expression of cv. Pinot Noir significantly up-regulated in 25 DAF. Our data provided new insights into PCD by identifying the grape metacaspase gene family and provide a useful reference for further functional analysis of metacaspases in grape.     

The relationship between colonisation and crown rot symptoms in strawberry plants infected with Phytophthora cactorum

Strawberry tissues infected with Phytophthora cactorum were comminuted and plated in a selective antibiotic agar medium to determine levels of tissue colonisation as indicated by the number of colony forming units (CFU) recovered per gramme of infected tissue. The number of CFU recovered per gramme of tissue increased logarithmically with the amount of necrosis in infected crown, leaf and petiole tissues. Under the conditions of enhanced susceptibility to infection and colonisation caused by cold storage treatments, this relationship between colonisation and necrosis was not significantly altered in the susceptible cv. Tamella. A recovery index was used to determine the effect of infected tissues on the recovery of CFU. This indicated that increasing levels of host colonisation stimulated CFU recovery and may partly explain the large increase in CFU g^-1 with larger amounts of necrosis. The amount of tissue colonisation was greater in inoculated plants of the susceptible cv. Tamella than in less susceptible cv. Cambridge Favourite, although the necrotic tissues of the latter contained more CFU g^-1, indicating a greater level of tolerance to colonisation. In cv. Tamella small amounts of colonisation were capable of causing wilt symptoms, although no wilted plants contained less than 200 CFU g^-1. Conversely, plants containing more than 1000 CFU g^-1 always wilted. In the early stages of infection, low levels of colonisation could be detected in strawberry crowns in the absence of symptoms. Dormant strawberry plants of cv. Tamella were readily infected by P. cactorum zoospore inoculations but, unlike actively growing plants, the majority of infections remained latent. These latent infections exhibited little or no symptoms and CFU recoveries from infected tissues were always below 100 CFU g^-1.     

Phosphorus export from roots to shoots of barley, buckwheat and rape seedlings with different P status

Seedlings of barley (Hordeum vulgare L. cvs Salka and Zita), buckwheat (Fagopyrum esculentum Moench) and rape (Brassica napus L. ssp. napus cv. Line) were grown in complete nutrient solutions with 8 or 10 different P concentrations in the range of 0–2 mM. Phosphate export from roots to shoots was determined from the amount of ³²P (or ³³P) absorbed and exported to shoots in 1 h from a nutrient solution containing 0.1 mM radiolabelled phosphate. P export was also determined in the presence of a metabolic uncoupler (DNP, 2.4-dinitrophenol) and a protein synthesis inhibitor (CH, cycloheximide). Phosphorus export from roots to shoots reached a maximum at a certain optimum level of phosphorus in shoots and roots, and decreased at both higher and lower P levels. Maxinmm P export was 1.7 ± 0.2 and 4.5 ± 0.5 (mean ±se of the three species) times higher than the P export at the lowest and highest [P]_root, respectively. Hill plots as well as plots of the untransformed decreasing P export vs root or shoot P concentrations above the optimum were linear and had high correlation coefficients. The Hill coefficient (n_H) based on [P]_root, was —7.7 for barley cv. Salka and varied between -3.8 and -4.5 for the other species. Based on [P]_shootot n_H was—16.1 for barley cv. Salka, -3.7 for barley cv. Zita and -6.4 for the two dicotyledonous species. Relative to the amount of P simultaneously absorbed by the root system, the import of P per unit shoot weight decreased linearly over the whole range of shoot P concentrations in the dicotyledonous species. In contrast, the relative import of P per unit shoot weight of the two barley cultivars increased at low levels of [P]_shoot and decreased at higher levels. DNP and CH almost eliminated P export from roots to shoots of seedlings with low or high P status. In seedlings with medium P status only 60 to 75% of the P export was affected.     

Ecophysiological and morphological adaption to soil flooding of two poplar clones differing in flood-tolerance

Responses to soil flooding of two poplar clones differing in flood-tolerance were studied to elucidate ecophysiological and morphological adaptation to hypoxia. Results showed that Populus deltoides cv. Lux ex. I-69/55 (Lux) was flood-tolerant, whereas P. simonii was flood-susceptible, based on structural and functional differences. They differed in morphological, ecophysiological, and anatomical characteristics when subjected to flooding. The difference between cv. Lux and P. simonii became particular obvious with increased length of the flooding period (8–22 days), but responses to flooding differed already during the first week of flooding. Ecophysiologically, in the beginning of flooding cv. Lux kept a high level of photosynthesis, showed a high free water content and water use efficiency at reduced leaf conductances and leaf water potentials. Chlorophyll content of cv. Lux was reduced so that sunlight absorption was lower as well and destruction of the photosynthesis system by photooxidation was avoided. Free protein content of Lux under flooding was also low, probably in favor of synthesis of other substances that enforce flood tolerance. On the contrary, in P. simonii transpiration only slowly decreased due to slow stomatal closure of leaves in the first day of flooding, and water potential decreased slowly, accompanied with high transformation rate of free water into bound water and low water use efficiency. Slow decomposition of chlorophyll of P. simonii resulted in overabundant light energy absorption and serious destruction of photosynthesis system II (PSII). Net photosynthesis of P. simonii seriously decreased under flooding. At the morphological level, cv. Lux developed many small and obviously functional hypertrophied lenticels throughout the flooding treatment. Bigger hypertrophied lenticels of P. simonii inclined to become rotten. Under complete submergency, cv. Lux could keep an intact leaf structure, whereas epidermis and structure of leaves of P. simonii were destroyed severely. Anatomically, the ultrastructures of leaves of cv. Lux were still intact at the end of flooding, whereas those of P. simonii were destroyed seriously, and many organelles were decomposed.     

Synergistic effects of drought and ascorbic acid on growth,mineral nutrients and oxidative defense system in canola (Brassica napus L.) plants

A study was conducted to find out the role of ascorbic acid (AsA) in modulating growth and different physio-biochemical attributes of canola plants under well-watered as well as water-deficit conditions. Drought stress imposed on 60 % field capacity significantly decreased the shoot and root fresh and dry weights, leaf chlorophyll contents, shoot and root P, root K⁺, and activity of CAT enzyme, while increased chlorophyll a/b contents, MDA, NPQ, leaf total phenolics, free proline and GB contents in both canola cultivars. Foliar-applied varying levels (50, 100 and 150 mg L^?1) of AsA enhanced shoot and root fresh and root dry weights, qN, NPQ, shoot and root P, AsA as well as the activity of POD enzyme particularly under drought stress conditions. Of both canola cultivars, cv. Dunkeld was higher in shoot fresh weights, ETR and F _v /F _m, MDA, proline and GB contents, and POD activity, however, cv. Cyclone in total phenolics and qN under well-watered and water-deficit conditions. Overall, the foliar-applied AsA had a positive effect, though not marked, on salt sensitive cv. Cyclone in terms of improved growth and other attributes, whereas exogenously applied AsA had a non-significant effect on relatively salt tolerant cv. Dunkeld.     

Phytochrome Characterization by Rabbit Antiserum against High Molecular Weight Phytochrome

Both small and large sizes of phytochrome purified from Garry oat (Avena sativa L. ev. Garry) as well as large phytochrome purified from Newton oat (A. sativa L. cv. Newton), rye (Secale cereale L. cv. Balbo), barley (Hordeum vulgare L. cv. Harrison), and pea (Pisum sativum L. cv. Alaska) seedlings are characterized by a specific antiserum against large Garry oat phytochrome. A spur is observed by double diffusion assay against large and small Garry oat phytochrome indicating only partial identity. In micro-complement fixation assays, large Garry oat phytochrome yields greater activity than small Garry oat phytochrome. In addition, the peak of activity is shifted to a higher antigen concentration with small phytochrome. Phytochrome, red-absorbing form, and phytochrome, far redabsorbing form, are indistinguishable by both double diffusion and micro-complement fixation assay. The different grass phytochromes are antigenically identical by double diffusion assay. Immunoelectrophoretic analyses of oat and rye large phytochrome, after proteolysis, suggest that there are one or a few regions of the molecule especially susceptible to hydrolysis by a wide variety of endopeptidases.     

Photosynthesis and PSII functionality of drought-resistant and drought-sensitive weeping lovegrass plants

World areas subject to drought are expected to increase under conditions of climate change. The purpose of this study is to clarify the response of grass species that can grow and produce under water stress. Therefore leaf photosynthesis, chlorophyll fluorescence and pigment content response to water stress were studied in two varieties of the C₄ grass Eragrostis curvula. Two-year-old plants of cv Ermelo and Consol were grown in plastic pots. Drought stress was imposed by withholding irrigation for 15 days and then rewatering for 5 days. During drought relative water content (RWC) decreased 65% in cv Ermelo, while lower reductions of RWC were observed in cv Consol. During the experiment in cv Ermelo increasing drought stress severity caused large decreases in photosynthetic rates, maximal PSII photochemical efficiency (F_V/F_M) and leaf pigment content. Cv Consol showed small variations in these parameters. Compared to cv Consol, after 15 days of drought, effective PSII quantum yield (Φ_II) was significantly lower in cv Ermelo. Reductions of Φ_II were related to significant reductions of open PSII energy capture efficiency (F′_V/F′_M). Photosynthetic response to increasing PPFD levels and to internal CO₂ concentration (C_i) were reduced by drought in cv Ermelo. Compared to well-watered control plants and to cv Consol, drought stressed plants of cv Ermelo showed also reductions of the initial slope of photosynthetic response to C_i and in the photosynthetic rate measured at saturating C_i. Moreover stomatal conductance (g) of both cvs decreased during drought. However, g was lower in drought stressed plants of cv Consol than in cv Ermelo. Water stress caused large reductions in leaf chlorophyll and carotenoid content in cv Ermelo, and small reductions in cv Consol. In drought-sensitive cv Ermelo water stress reduced the capabilities to down regulate PSII functionality through thermal energy dissipation. Results suggest that drought resistance of cv Consol, can be attributed to a higher water use efficiency.     

Differential host growth regulation by the solitary endoparasitoid, Meteorus pulchricornis in two hosts of greatly differing mass

Solitary koinobiont endoparasitoids generally reduce the growth of their hosts by a significant amount compared with healthy larvae. Here, we compared the development and host usage strategies of the solitary koinobiont endoparasitoid, Meteorus pulchricornis, when developing in larvae of a large host species (Mythimna separata) and a much smaller host species (Plutella xylostella). Caterpillars of M. separata were parasitized as L2 and P. xylostella as L3, when they weighed approximately 2 mg. The growth of parasitized M. separata larvae was reduced by almost 95% compared with controls, whereas parasitized P. xylostella larvae grew some 30% larger than controls. Still, adult wasps emerging from M. separata larvae were almost twice as large as wasps emerging from P. xylostella larvae, had larger egg loads after 5 days and produced more progeny. Survival to eclosion was also higher on M. separata than on P. xylostella, although parasitoids developed significantly faster when developing on P. xylostella. Our results provide evidence that koinobionts are able to differentially regulate the growth of different host species. However, there are clearly also limitations in the ability of parasitoids to regulate phenotypic host traits when size differences between different host species are as extreme as demonstrated here.     

Factors permitting prolonged translation by isolated pea chloroplasts

The following parameters were found to prolong the time-course of translation by isolated pea (Pisum sativum, cv Progress No. 9) chloroplasts: addition of other amino acids (an effect synergistic with sufficient free Mg²⁺), use of lower light intensities, and additions of inorganic phosphate and ATP. In a chloroplast system which includes these parameters, active translation usually extends to almost an hour. The total amount of leucine incorporated is routinely 60 to 100 nanomoles/milligram chlorophyll and often 200 nanomoles/milligram chlorophyll. Accurate estimation of the amount of amino acid incorporated depends on supplying the labeled amino acid at a concentration sufficient to overcome isotope dilution effects from endogenous pools. Approximately 39 thylakoid and 60 stroma polypeptides were visible on autoradiographs after labeling with [³⁵S]methionine. Label in a few of the polypeptide bands was increased or decreased by specific changes in the reaction conditions. Due to the long period of activity and the large number of labeled products, this chloroplast system should be useful for future studies of chloroplast translation.     

Resistance in Lycopersicon peruvianum to Isolates of Mi Gene-Compatible Meloidogyne Populations

Root-knot nematode resistance of F₁ progeny of an intraspecific hybrid (Lycopersicon peruvianum var. glandulosum Acc. No. 126443 x L. peruvianum Acc. No. 270435), L. esculentum cv. Piersol (possessing resistance gene Mi), and L. esculentum cv. St. Pierre (susceptible) was compared. Resistance to 1) isolates of two Meloidogyne incognita populations artificially selected for parasitism on tomato plants possessing the Mi gene, 2) the wild type parent populations, 3) four naturally occurring resistance (Mi gene)-breaking populations of M. incognita, M. arenaria, and two undesignated Meloidogyne spp., and 4) a population of M. hapla was indexed by numbers of egg masses produced on root systems in a greenhouse experiment. Artificially selected M. incognita isolates reproduced abundantly on Piersol, but not (P = 0.01) on resistant F₁ hybrids. Thus, the gene(s) for resistance in the F₁ hybrid differs from the Mi gene in Piersol. Four naturally occurring resistance-breaking populations reproduced extensively on Piersol and on the F₁ hybrid, demonstrating ability to circumvent both types of resistance. Meloidogyne hapla reproduced on F₁ hybrid plants, but at significantly (P = 0.01) lower levels than on Piersol.     

Improvement in Oil Production by Increasing Malonyl-CoA and Glycerol-3-Phosphate Pools in Scenedesmus quadricauda

In recent years, microalgae have attracted considerable interest as a biofuel resource owing to their rapid growth, tolerance to harsh conditions, and ability to accumulate a large amount of triacylglycerols (TAGs). However, the economic effectiveness of algal biofuel is still low. In this study, we attempted to increase oil production of the microalga Scenedesmus quadricauda by elevating intracellular malonyl-CoA and glycerol-3-phosphate (G3P) pools. To increase intracellular oil content, yeast-derived genes encoding acetyl-CoA carboxylase (ACC1), glycerol kinase (GPD1), and glycerol-3-phosphate dehydrogenase (GUT1) were overexpressed under the control of CaMV 35S and NOS promoters with SV40 large T antigen components. Fatty acid profiling, G3P content, and the number of cells with high oil content were analyzed by gas chromatography-mass spectrometry, G3P assay kit, and flow cytometry, respectively. Overexpression of ACC1 increased the total fatty acid content by 1.6-fold. Overexpression of GPD1 and GUT1 increased intracellular G3P content by 1.6- and 1.9-fold, respectively. Multi-gene expression of ACC1, GPD1, and GUT1 increased the number of cells with high oil content by 1.45-fold compared with that observed with the wild-type. This study is the first to report increased oil production by overexpression of the key genes (ACC1, GPD1, and GUT1) for TAG biosynthesis in microalgae.

Electronic supplementary material

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