Days Of Co-cultivation Research Articles

Efficient production of transgenic melon via Agrobacterium-mediated transformation.

Oriental melon (Cucumis melo L. var. makuwa) is an important fruit for human consumption. However, this plant species is one of the most recalcitrant to genetic transformation. The lack of an efficient in vitro system limits the development of a reproducible genetic transformation protocol for Oriental melon. In this study, an efficient transgenic production method for Agrobacterium-mediated transformation using cotyledon explants of Oriental melon was developed. Cotyledon explants were pre-cultivated for two days in the dark, and the optimal conditions for transformation of melon were determined to be a bacteria concentration of OD600 0.6, inoculation for 30 min, and two days of co-cultivation. Transgenic melon plants were produced from kanamycin-resistant shoots. A total of 11 independent transgenic plants were regenerated with a transformation efficiency of 0.8% of the inoculated explants. The transgenic plants were phenotypically normal and fully fertile, which might be a consequence of the co-cultivation time.

Agrobacterium tumefaciens-mediated transformation of bush monkey-flower (Mimulus aurantiacus Curtis) with a new reporter gene ZsGreen

A successful in vitro Agrobacterium-mediated transformation protocol was developed for Mimulus aurantiacus, a model species for ecological and evolutionary genetics and a promising ornamental plant. Three binary vectors were tested, each containing the hptII selectable marker gene and one of the reporter genes: gusA, EGFP or ZsGreen, all of them under CaMV 35S promoter. Genetic transformation was achieved through 4 days of co-cultivation of leaf, petiole and hypocotyl explants with Agrobacterium tumefaciens strain LBA 4404. Explants produced transformed callus tissue on solid modified Murashige and Skoog medium supplemented with 1 mg L−1 6-benzylaminopurine, 0.5 mg L−1 1-naphthaleneacetic acid, 30 g L−1 sucrose and 20 or 50 mg L−1 hygromycin B. All three reporter genes were expressed in callus tissue but the intensity of expression gradually decreased during further plant development. The new reporter gene ZsGreen proved suitable for plant transformation experiments since very intense and bright fluorescence was detected. Out of 1,760 co-cultured explants, 110 plants were regenerated and all of them were found to be PCR positive for the selection and/or reporter genes. Chemiluminescent Southern blot analysis revealed that 91 % of the regenerated plants (100 T0 plants) contained T-DNA integrated in their genome. Transformation efficiency varied from 1.4 to 23.3 % for hypocotyl and petiole explants, respectively. Integration of some backbone sequences in plant genomes was confirmed in 75.3 % of T0 plants. Using this protocol, stable transformants expressing selectable marker gene hptII and one of the reporter genes (gusA, ZsGreen or EGFP) were obtained in 4–5 months.

A survey on optimization of Agrobacterium-mediated genetic transformation (AtMT) of Colletotrichum gloeosporioides

The fungus Colletotrichum gloeosporioides is the causative agent of anthracnose disease of many tropical, subtropical and temperate fruits, and a microbial source of the anticancer drug, Taxol. Here, we introduce an optimized Agrobacterium tumefaciens-mediated transformation (ATMT) protocol for genetic manipulation of this fungus using hph and gfp-tagged hph genes as selection markers. Results showed that falcate spores can be easily used instead of protoplasts for transformation. Several experimental parameters were shown to affect transformation efficiencies, among which the length of co-cultivation, the ratio of fungal conidia to bacterium during co-cultivation, the kind of membrane during co-cultivation, and the kind of fungal growth medium during transformants selection, showed the highest influences on ATMT frequencies. Results indicated that the optimal ATMT of C. gloeosporioides was achived after 3 days of co-cultivation, at 107 per ml fungal conidia, via the use of Fabriano 808 filter paper and Czapek's culture medium. Successive subculturing of transformants on selective and non-selective media demonstrated the stable expression of transgens, and subsequent PCR based analyses of transformants revealed the presence (100%) of transferred genes. Flourescence microscopy analyses showed a punctuate pattern for localization of an expressed Gfp-tagged Hph protein inside fungal hyphae. The optimized ATMT protocol generated mutants that showed different phenotypes based on their vegetation and pigmentation. This suggests the possible applicability of this technique for functional genetics studies in C. gloeosporioides, through insertional mutagenesis.

Genetic Improvement of Sugarcane for Drought and Salinity Stress Tolerance Using Arabidopsis Vacuolar Pyrophosphatase (AVP1) Gene

Sugarcane plant is a glycophyte, hence its growth and sucrose contents are severely affected by drought and salinity stresses. Bioengineering approaches offer a plausible and rapid solution to mitigate these losses. Therefore for genetic improvement of sugarcane against these stresses, the present study was conceived to transform Arabidopsis Vacuolar Pyrophosphatase (AVP1) gene--confers tolerance against drought and salinity--into sugarcane through Agrobacterium. For this purpose, highly regenerable apical buds of sugarcane variety CP77-400 were used as explants. EHA105 strain of Agrobacterium harboring pGreen0029 vector containing AVP1 gene driven under 35SCaMV promoter was employed for transformation. The key factors studied include application of acetosyringone, cefotaxime, kanamycin, and co-cultivation period for successful transformation. Maximum regeneration frequency of 77.5 % was achieved on MS media containing 1 mg/l BAP, 1 mg/l Kn, 1 mg/l GA₃, 0.25 mg/l NAA, 50 μM acetosyringone, 500 mg/l cefotaxime, and 150 mg/l kanamycin on 3 days of co-cultivation. The results revealed that apical buds are distinctive viable tissues for sugarcane transformation and regeneration to produce a large number of CP77-400 transgenic plants in shorter period of time without intervening mosaics and chimeras. The AVP1 transcripts expression in transgenic lines at various levels was detected by RT-PCR. Longer and profuse root system was observed in transgenic plants in comparison with control plants. Concomitantly, only transgenic plants were able to withstand higher NaCl salt stress as well as scarcity of water thus, showing tolerance against salinity and drought stresses.

The influence of bone marrow- and synovium-derived mesenchymal stromal cells from osteoarthritis patients on regulatory T cells in co-culture

There is increasing evidence that inflammation in the synovium plays a major role in the progression of osteoarthritis (OA). However, the immunogenic properties of mesenchymal stromal cells (MSCs), which are considered to regulate immunity in various diseases, remain largely unknown in OA. The purpose of this study was to determine the influence of MSCs from OA patients on regulatory T cells (Tregs ) in an allogeneic co-culture model. Bone marrow (BM) and synovial membrane (SM) were harvested from hip joints of OA patients and co-cultured with lymphocytes enriched in CD4(+) CD25(+) CD127(-) regulatory T cells (Treg (+) LC) from healthy donors. Treg proportions and MSC markers were assessed by flow cytometry. Cytokine levels were assessed after 2 and 5 days of co-cultivation. Additionally, Treg (+) LC cultures were analysed in the presence of interleukin (IL)-6 and MSC-supernatant complemented medium. B-MSCs and S-MSCs were able to retain the Treg proportion compared to lymphocyte monocultures. T cell-MSC co-cultures showed a significant increase of IL-6 compared to MSC cultures. S-MSCs produced higher amounts of IL-6 compared to B-MSCs, both in single and T cell co-cultures. The effect of retaining the Treg percentage could be reproduced partially by IL-6 addition to the medium, but could only be observed fully when using MSC culture supernatants. Our data demonstrate that retaining the Treg phenotype in MSC-T cell co-cultures can be mediated by MSC derived from OA patients. IL-6 plays an important role in mediating these processes. To our knowledge, this study is the first describing the interaction of MSCs from OA patients and Tregs in an allogeneic co-culture model.

액체배양을 이용한 단기 벼 형질전환 방법

본 연구는 종자로부터 유도된 캘러스를 아그로박테리움을 이용해 감염하여 고체배지에서 배양하는 기존의 방법과 달리, 형질전환에 소모되는 노동력과 시간, 비용을 단축하고자 감염과 공동배양, 균제거와 캘러스 선발까지 액체배양을 시도하였다. 성숙 종자로부터 유도된 캘러스를 바로 아그로박테리움으로 감염함으로써 조직배양으로 인한 체세포 변이의 발생을 최소화하고 감염부터 그 후 캘러스선발까지 총 4단계의 시간과 비용을 최소화하였으며, 감염된 캘러스로부터 재분화 시킴으로써 형질전환 식물체를 얻는 방법을 새롭게 수립하였다. 배양과정 중 감염과 공동배양 기간을 3일로 단축시킴으로써 캘러스의 스트레스를 최소화 하였고, PCR 분석을 통해 원하는 목표 유전자가 형질전환체에 안정적으로 도입이 되는 것도 확인할 수 있었다. 이러한 결과를 종합해 볼 때, 본 실험을 통해 얻어진 새로운 액체배양 방법은 우수한 농업적 형질을 가진 벼 품종 개발시 효율적으로 이용할 수 있을 것으로 생각된다. Rice is one of the most important cereal crops as a model plant for functional genomics of monocotyledons and usually transformed using Agrobacterium tumefaciens. However, the transformation's process using previous method is still time consuming and uneconomical, low efficiency. In this study, we established a new method by modifying the general Agrobacterium protocol especially in the infection and co-cultivation, Agrobacterium elimination, infected calli's selection steps using liquid media. We directly inoculated Agrobacterium containing a ZjLsL gene under the control of constitutive promoter into the 1- to 3-week-old rice calli derived from mature seeds. After 3 days of co-cultivation, the infected calli were transferred onto liquid media of Agrobacterium elimination and calli's selection for 3 days. The calli were transferred to calli's growth solid media for 14 days and then the calli transferred to shoot induction and root induction media. Putative transformants were initially selected on the medium containing phosphinothricin, and the PAT protein verified by PAT strip test. This method in this study would lead to reduction of substantial labor and time to generate transgenic plants.

A novel actinomycete Streptomyces aurantiogriseus with algicidal activity against the toxic cyanobacterium Microcystis aeruginosa

A novel actinomycete strain (PK1) was isolated from soil in Khon Kaen Province, Thailand, and was capable of inhibiting the cyanobacterium Microcystis aeruginosa. The isolate PK1 was identified as Streptomyces aurantiogriseus based on an analysis of biochemical and morphological characteristics and 16S rDNA sequence. The algicidal activity of PK1 against M. aeruginosa depended on the growth phase of PK1, but not on the cyanobacterial growth phase. Stationary growth phase cultures of the strain PK1 exhibited the highest anti-Microcystis activity when co-cultivated with M. aeruginosa. Complete growth inhibition was observed after 8 days of co-cultivation in liquid culture medium. The algicidal compounds were extracted from PK1 with ethyl acetate and then purified by silica gel column chromatography. These partially purified compounds demonstrated algicidal activity against M. aeruginosa, suggesting that the strain PK1 provides a potential source of extracellular compounds for the control of M. aeruginosa bloom. This is the first report of anti-cyanobacterial activity from the soil actinomycete S. aurantiogriseus.

A new system using Solanum tuberosum for the co-cultivation of Glomus intraradices and its potential for mass producing spores of arbuscular mycorrhizal fungi

Freshly harvested potato tubers, Solanum tuberosum var ‘Pukhraj’, were inoculated for transformation with Agrobacterium rhizogenes strain Ri1600. Hairy roots were formed after 8 days of co-cultivation and the transformation efficiency was 40 %. The transformants were transferred from Murashige and Skoog medium (MS) to Modified White’s medium (MW) and finally on a hormone-free minimal medium (M). The putative transformants were confirmed using rolA and rolB gene specific primers for the polymerase chain reaction (PCR) analysis. The root inducing (Ri) T-DNA transformed potato roots were co-cultured with Glomus intraradices (CMCCROC7) to obtain arbuscular mycorrhizal root organ cultures (AM-ROC dual cultures), which were used for studying the symbiosis with Glomus intraradices and the potential for spore production in vitro. Sporulation was comparable with the existing in vitro carrot-dual culture system. Around 60,250 spores/jar could be harvested with around 38,314 extraradical spores/jar and around 21,936 intraradical spores/jar. The new method using potato is certainly promising for the mass production of mycorrhizal biofertilizers. The viability of the spores when tested on potato roots was nearly 100 % and more than half of the roots were colonized 12 weeks after inoculation.

Establishment of Agrobacterium-mediated genetic transformation system in Dahlia

An efficient system for Agrobacterium-mediated transformation was established in dahlia (Dahlia×pinnata) ‘Yamatohime’. Mass of shoot primordia (MSP) induced on MS medium supplemented with 10 mg l−1 TDZ were inoculated with Agrobacterium tumefaciens strain EHA101 (pIG121-Hm) harboring both β-glucuronidase (GUS) and hygromycin resistant genes. After 2 days of co-cultivation, the MSP were transferred to a selection medium containing hygromycin with meropenem for bacterial elimination. Shoots were successfully regenerated from survived MSP on hormone-free medium without hygromycin and they rooted on hormone-free medium containing hygromycin. The hygromycin-resistant plants thus obtained showed histochemical blue staining for GUS. Transformation of plants was confirmed by PCR and Southern blot analyses. Transgenic ‘Kokucho’ were also produced by using the same transformation procedure, suggesting wide applicability of this Agrobacterium-mediated transformation procedure for other dahlia cultivars.

Agrobacterium-mediated genetic transformation of selected tropical inbred and hybrid maize (Zea mays L.) lines

The study was carried out to evaluate the amenability of tropical inbred and hybrid maize lines, using Agrobacterium mediated transformation technique. Agrobacteriumtumefaciens strains EHA101 harbouring a pTF102 binary vector, EHA101, AGL1, and LBA4404 harbouring pBECK2000.4 plasmid, LBA4404, GV and EHA105 harbouring pCAMBIA2301 plasmid, and AGL1 harbouring the pSB223 plasmid were used. Delivery of transgenes into plant tissues was assessed using transient β-glucuronidase (gus) activity on the 3rd and 4th day of co-cultivation of the infected Immature Zygotic Embryos (IZEs) and embryogenic callus. Transient gus expression was influenced by the co-cultivation period, maize genotype and Agrobacterium strain. The expression was highest after the 3rd day of co-culture compared to the 4th day with intense blue staining was detected for IZEs which were infected with Agrobacterium strains EHA105 harbouring pCAMBIA2301 and EHA101 harbouring pTF102 vector. Putative transformants (To) were regenerated from bialaphos resistant callus. Differences were detected on the number of putative transformants regenerated among the maize lines. Polymerase chain reaction (PCR) amplification of Phosphinothricin acetyltransferase (bar) and gus gene confirmed the transfer of the transgenes into the maize cells. Southern blot hybridization confirmed stable integration of gus into PTL02 maize genome and segregation analysis confirmed the inheritance of the gus. A transformation efficiency of 1.4 % was achieved. This transformation system can be used to introduce genes of interest into tropical maize lines for genetic improvement.

Efficiency of different Agrobacterium rhizogenes strains on hairy roots induction in Solanum mammosum

This article presents the abilities and efficiencies of five different strains of Agrobacterium rhizogenes (strain ATCC 31798, ATCC 43057, AR12, A4 and A13) to induce hairy roots on Solanum mammosum through genetic transformation. There is significant difference in the transformation efficiency (average number of days of hairy root induction) and transformation frequency for all strains of A. rhizogenes (P < 0.05). Both A. rhizogenes strain AR12 and A13 were able to induce hairy root at 6 days of co-cultivation, which were the fastest among those tested. However, the transformation frequencies of all five strains were below 30 %, with A. rhizogenes strain A4 and A13 showing the highest, which were 21.41 ± 10.60 % and 21.43 ± 8.13 % respectively. Subsequently, the cultures for five different hairy root lines generated by five different strains of bacteria were established. However, different hairy root lines showed different growth index under the same culture condition, with the hairy root lines induced by A. rhizogenes strain ATCC 31798 exhibited largest increase in fresh biomass at 45 days of culture under 16 h light/8 h dark photoperiod in half-strength MS medium. The slowest growing hairy root line, which was previously induced by A. rhizogenes strain A13, when cultured in optimized half-strength MS medium containing 1.5 times the standard amount of ammonium nitrate and potassium nitrate and 5 % (w/v) sucrose, had exhibited improvement in growth index, that is, the fresh biomass was almost double as compared to its initial growth in unmodified half-strength MS medium.

Neuronal differentiation of human iPS-cells in a rat cortical primary culture.

We tested the neuronal differentiation of human iPS-cells under in vitro conditions. For this purpose we pre-differentiated human (h) iPS-cells into neural stem cells and co-cultivated them with a cortical primary culture from embryonic rats. After 2 days of co-cultivation a certain number of hiPS-cells exhibited a clear neuronal morphology combined with expression of betaIII-tubulin and doublecortin. In addition, we found hiPS-cells without neuronal differentiation and cells already expressing betaIII-tubulin but not having yet distinctive axonal and dendritic processes. Human neuronal progenitors, starting neuronal differentiation, were contacted by both neuronal processes from rat neurons and oligodendrocytes, indicating a possible instructive influence by the primary culture on human cells. After 7 days of co-cultivation, however, we observed a complete degeneration of human iPS-derived cells and phagocytosis by microglial cells. Immunocytochemical stainings surprisingly revealed that microglial cells of the cortical primary culture express both CD8 and T-cell receptors.

A study one isopentenyl transferase gene by using Agrobacterium tumefaciens to increase the longevity of carnation (Dianthus caryophyllus L.)

In vitro leaves of carnation (cut-off flower) variety CCF cut into small pieces about 1x1cm in size were precultured for 5 days and were co-cultivated with the Agrobacterium tumefaciens strain LBA 4404 harbouring the plasmid pVDH1396 contained the β-glucuronida gene (gusA), hygromycin phosphotransferase gene (hpt) under the control of cauliflower Mosaic virus 35S promoters, terminators, and an isopentenyl transferase (ipt) gene from Agrobacterium tumefaciens, driven by the SAG12 promoter from senescence associated gene 12 of Arabidopsis thaliana and its terminator. After 5 days of co-cultivation, explants were transferred onto the MS selection medium containing 1.0mg/l TDZ and 0.1mg/l NAA, 5mg/l hygromycin, 500 mg/l cefotaxime. Some putative shoots were tested for GUS assay. Putative shoots were transferred on MS medium 3 containing 0.5 mg/l IBA and 10 mg/l hygromycin. PCR analyses on hygromycin resistant shoots generated via Agrobacterium tumefaciens transformation to confirm the presence of the, ipt, hpt and gusA genes with expected bands 615bp, 508bp and 365bp. Analysis of putative carnation transformants to confirm that the foreign genes are inserted into the carnation genome by Southern blot analyses will be done in the future.

An efficient and universal Agrobacterium-mediated transformation protocol in rice

For development of transgenic varieties of interest in rice, we have developed a simple, efficient and universal Agrobacterium mediated transformation protocol. Mature seeds of two indica (IR64 and Jaya), one each from japonica (AC41039) and aromatic (Basmati370) varieties were used as explants in the present study. Agrobacterium tumefaciens strain EHA 105 carrying Ti plasmid (pBI121) with the selectable marker nptII along with the reporter gene uidA encoding β-glucuronidase (GUS) was successfully integrated with rice genome without use of acetosyringone. Sterile distilled water washing in place of cefotaxime in the elimination process has been used to control excess growth of Agrobacterium. All the material after transformation germinated in 2 to 3 days of co-cultivation on MS basal medium. Germinated seeds transferred to the selection medium i.e. plain MS medium with 50 mg/l of kanamycin, produced two to three primary tillers within 2 weeks. Mesocotyls from 2 week old in vitro grown plants were taken and cultured in the multiplication medium (MS supplemented with 0.5 mg/l BA and 50 mg/l Kanamycin) where within 6–8 days they produced 3–4 secondary tillers. All the five to six tiller shoots so produced in the process developed roots on plain MS and grew well when transferred to pots containing autoclaved soil and vermicompost in the proportion of 4:1. Transient expression of GUS was observed in all the tissues of recipient plants. Integration of the transgene was confirmed by employing southern blotting and real-time PCR technique. The transformation protocol developed can be efficiently used across the two major subspecies/ecotypes of the Asian rice cultivar Oryza sativa.

PRODUCTION OF TRANSGENIC CUCUMBER PLANTLETS CONTAINING SEQUENCES FROM WATERMELON MOSAIC VIRUS-II FUSED WITH GFP GENE

Cucumber (Cucumis sativus L. cv. Faris) explants were transformed by LBA4404 strain of Agrobacterium tumefaciens harboring the binary vector pPZPnptCat-WMV. The T-DNA region contains Neomycin Phosphotransferase II (NPT II) as a selectable marker gene and sequences of Watermelon Mosaic Virus-II (WMV-II) fused with Green Fluorcent Protein (GFP) gene under control of 35S promoter. Agrobacterium-mediated transformation was optimized using GFP as a reporter gene. The optimized parameters were Agrobacterium concentration, preculture period, co-cultivation period and immersion time. Results were recorded based on the percentage of green fluorescent protein (GFP) expression. Agrobacterium concentration at (OD 600 nm 0.8), four days of pre-culture, three days of co-cultivation and sixty minutes of immersion time gave the highest percentage of GFP areas (78%, 46%, 82% and 52%, respectively). Cotyledon was the best explants to give the highest percentage of GFP areas in all tested parameters. Following co-cultivation, leaf, cotyledon, callus and shoot-tip explants were cultured on selective and regeneration Murashige and Skoog (MS) medium containing 1mg/L 6-Benzylaminopurine (BA), 200 mg/L kanamycin and 300 mg/L cefotaxime. Kanamycin resistant shoots were induced from these explants after four weeks. Putative transgenic plantlets were produced from leaf, cotyledon and shoot-tip explants at 8 weeks and at 12 weeks from callus. Integration of the transgenes in the cucumber genome was confirmed by PCR analysis. This study showed that the Agrobacterium-mediated gene transfer system and regeneration via organogenesis is an effective method for producing transgenic cucumber plantlets. Cloning construct of Catgfp-WMV-2 into binary vector pPZPnpt was done successfully. Agrobacterium concentration at 0.8, four days of pre-culture, three days of co-cultivation and sixty minutes of immersion time gave the highest number of GFP positive percentage (78%, 46%, 82% and 52%, respectively). Cotyledon was the best explants to give the highest number of GFP positive percentage in all tested parameters. Putative transgenic plantlets were obtained from (leaf, cotyledon and shoot-tip explants after 8 weeks) and after 12 weeks from callus.

Optimization of factors affecting Agrobacterium-mediated transformation of Micro-Tom tomatoes

Micro-Tom is the smallest known variety of tomatoes. An orthogonal experimental design L(16) (4(5)) was used to optimize Agrobacterium-mediated transformation of cotyledon explants of Lycopersicon esculentum cv. Micro-Tom. Four parameters were investigated to determine their effect on transformation frequency: the concentration of bacterial suspension, time of dip in bacterial suspension, co-cultivation time, and concentration of carbenicillin. We also examined the effect of these parameters on contamination rate, necrosis rate, mortality, cut-surface browning rate, and undamaged explant rate. Both the bacterial and carbenicillin concentrations had a significant influence on the rate of infected explants. The time of co-cultivation also had a significant influence on the transformation parameters. The optimal transformation protocol consisted of an Agrobacterium suspension of 0.5 × 10(8) cells/mL (OD(600) = 0.5) and an infection time of 5 min, one day of co-cultivation and 500 mg/L carbenicillin. Under these conditions, the transformation efficiency of the shoots reached 5.1%; the mean transformation frequency was 3.9% (N = 838).

Optimization of micropropagation and &amp;lt;i&amp;gt;Agrobacterium&amp;lt;/i&amp;gt;-mediated gene transformation to spinach (&amp;lt;i&amp;gt;Spinacia oleracea&amp;lt;/i&amp;gt; L.)

Spinach is one of the dioecious plant which is considered as a model plant in genetic and molecular studies of sex determination because of its special characteristics such as low chromosome number and short life cycle. An efficient protocol for Spinacia oleracea Agrobacterium-mediated gene transformation was developed. The leaf disks, roots, hypocotyls and cotyledons of this plant were inoculated with LBA4404. LBA4404 carrying pCAMBIA3301 binary vector with 35SCaMV gusint and 35SCaMV bar cassettes. Effects of two preparation condition (induction of vir genes and noninduction) were considered. Also effects of different number days of co-cultivation and pre-culture of explants were examined. After co-cultivation, the explants were transferred to regeneration medium containing 250 mg·L-1 Carbeniciline. Transient expression efficiency was calculated based on the number of blue spots per explants one week after inoculation. Based on the results of transient expression, stable transformation was carried out. After formation of callus the histochemical GUS assay was carried out on some parts of them and other parts were leaved for being regenerated.

接种后共培养时间对丛枝菌根喜树幼苗喜树碱含量的影响

Arbuscular mycorrhizal(AM) is the most widespread form of plant symbiosis and has been found to enhance photosynthesis rate,biomass accumulation,pathogen defense,and tolerance to heavy metals and cold stress.In addition,it affects the production of plant secondary metabolites,one of which is camptothecin,an anti-cancer compound used in clinical practice.Camptothecin is a water-insoluble cytotoxic monoterpene derived from indole alkaloid and was initially isolated from the Chinese tree Camptotheca acuminate(Nyssaceae).It has gained great attention for its remarkable inhibitory activity against tumor cells.Based on our previous study on the correlation between the formation of mycorrhiza and camptothecin content in mycorrhizal C.acuminata seedlings,the effect of co-cultivation time on camptothecin accumulation in C.acuminata seedlings after inoculation with Acaulospora mellea and Glomus intraradices was investigated in the present study.Seeds of C.acuminata were sterilized and sown in sterilized matrix(a mixture of soil and sand) in the greenhouse.Seedlings with similar height and crown size were selected and divided into three groups,inoculation with arbuscular mycorrhizal fungi A.mellea,inoculation with G.intraradices and mock inoculation control.Each group was divided into five sub-groups,with an inoculation of each sub-group every seven days.The seedlings were sampled at the seventh day of the last inoculation,i.e.the co-cultivation time of each subgroup was 35,28,21,14 and 7 days,respectively.Mycorrhizal colonization frequency,colonization intensity of roots and camptothecin contents and yields in C.acuminata seedlings were determined.The results showed that:(1) Camptothecin contents and yields in mycorrhizal seedlings increased significantly.This implies that the accumulation of camptothecin in C.acuminata seedlings was enhanced after inoculation with the two mycorrhizal fungi.(2) Camptothecin contents and yields in roots,stems,leaves and the whole plants increased with the co-cultivation time of C.acuminata seedlings with the mycorrhizal fungi.Camptothecin contents and yields in roots and stems of the two arbuscular mycorrhizal seedlings,and in leaves and whole plants of G.intraradices seedlings reached the highest levels after 21 days of co-cultivation,and then remained constant.While in leaves and whole plants of A.mellea seedlings camptothecin contents and yields were the highest on the 28th day after co-cultivation and dropped slightly thereafter.(3) Mycorrhizal colonization frequency and colonization intensity in two arbuscular mycorrhizal seedlings were enhanced with the increase of co-cultivation time till the 28th day,after which no significant differences were observed.Therefore,a significant correlation was observed between camptothecin contents and yields in C.acuminata seedlings and co-cultivation with arbuscular mycorrhizal fungi for up to 28 days.These results demonstrate that there is a precise correlation of camptothecin accumulation and fungal development.Our future studies will be focused on understanding of the fungal-dependent regulation of the temporal metabolic activities during mycorrhiza development and the spatial distribution of camptothecin in different tissues and cell types.Ultimately,we aim to conduct molecular genetics and engineering of camptothecin-AM fungus interactions.

Assessment of factors affecting Agrobacterium-mediated genetic transformation of the unicellular green alga, Chlorella vulgaris

The successful establishment of an Agrobacterium-mediated transformation method and optimisation of six critical parameters known to influence the efficacy of Agrobacterium T-DNA transfer in the unicellular microalga Chlorella vulgaris (UMT-M1) are reported. Agrobacterium tumefaciens strain LBA4404 harbouring the binary vector pCAMBIA1304 containing the gfp:gusA fusion reporter and a hygromycin phosphotransferase (hpt) selectable marker driven by the CaMV35S promoter were used for transformation. Transformation frequency was assessed by monitoring transient β-glucuronidase (GUS) expression 2 days post-infection. It was found that co-cultivation temperature at 24°C, co-cultivation medium at pH 5.5, 3 days of co-cultivation, 150 μM acetosyringone, Agrobacterium density of 1.0 units (OD(600)) and 2 days of pre-culture were optimum variables which produced the highest number of GUS-positive cells (8.8-20.1%) when each of these parameters was optimised individually. Transformation conducted with the combination of all optimal parameters above produced 25.0% of GUS-positive cells, which was almost a threefold increase from 8.9% obtained from un-optimised parameters. Evidence of transformation was further confirmed in 30% of 30 randomly-selected hygromycin B (20 mg L(-1)) resistant colonies by polymerase chain reaction (PCR) using gfp:gusA and hpt-specific primers. The developed transformation method is expected to facilitate the genetic improvement of this commercially-important microalga.

Improved Agrobacterium-mediated transformation of cowpea via sonication and vacuum infiltration

An improved method of Agrobacterium-mediated transformation of cowpea was developed employing both sonication and vacuum infiltration treatments. 4 day-old cotyledonary nodes were used as explants for co-cultivation with Agrobacterium tumefaciens strain EHA105 harbouring the binary vector pSouv-cry1Ac. Among the different injury treatments, vacuum infiltration and their combination treatments tested, sonication for 20 s followed by vacuum infiltration for 5 min with A. tumefaciens resulted in highest transient GUS expression efficiency (93% explants expressing GUS at regenerating sites). After 3 days of co-cultivation, the explants were cultured in 150 mg/l kanamycin-containing selection medium and putative transformed plants were recovered. The presence, integration and expression of nptII and cry1Ac genes in T0 transgenic plants were confirmed by polymerase chain reaction (PCR), genomic Southern and qualitative reverse transcription (RT)-PCR analysis. Western blot hybridization and enzyme-linked immunosorbent assay (ELISA) detected and demonstrated the accumulation of Cry1Ac protein in transgenic plants. The cry1Ac gene transmitted in a Mendelian fashion. The stable transformation efficiency increased by 88.4% using both sonication-assisted Agrobacterium-mediated transformation (SAAT) and vacuum infiltration than simple Agrobacterium-mediated transformation in cowpea.