Agrobacterium-transformed rice plants expressing synthetic cryIA(b) and cryIA(c) genes are highly toxic to striped stem borer and yellow stem borer

OsNAC121 regulates root development, tillering, panicle morphology, and grain filling in rice plant

Transcription factors in coordination with phytohormones form an intricate regulatory network modulating vital cellular mechanisms like development, growth and senescence in plants. In this study, we have functionally characterized the transcription factor OsNAC121 by developing gene silencing and overexpressing transgenic rice plants, followed by detailed analyses of the plant architecture. Transgenic lines exhibited remodelling in crown root development, lateral root structure and density, tiller height and number, panicle and grain morphologies, underpinning the imbalanced auxin: cytokinin ratio due to perturbed auxin transportation. Application of cytokinin, auxin and abscisic acid increased OsNAC121 gene expression nearly 17-, 6- and 91-folds, respectively. qRT-PCR results showed differential expressions of auxin and cytokinin pathway genes, implying their altered levels. A 47-fold higher expression level of OsNAC121 during milky stage in untransformed rice, compared to 14-day old shoot tissue, suggests its crucial role in grain filling; as evidenced by a large number of undeveloped grains produced by the gene silenced lines. Crippled gravitropic response by the transgenic plants indicates their impaired auxin transport. Bioinformatics revealed that OsNAC121 interacts with co-repressor (TOPLESS) proteins and forms a part of the inhibitor complex OsIAA10, an essential core component of auxin signalling pathway. Therefore, OsNAC121 emerges as an important regulator of various aspects of plant architecture through modulation of crosstalk between auxin and cytokinin, altering their concentration gradient in the meristematic zones, and consequently modifying different plant organogenesis processes.

Analysis of the Genetic Stability of Insect and Herbicide Resistance Genes in Transgenic Rice Lines: A Laboratory and Field Experiment

A lack of stability in the expression of Bacillus thuringiensis genes (CRY) and the dialaninophosphate resistance gene (BAR) in transgenic rice plants can lead to the loss of important characters. The genetic stability of transgenic expression in high-generation lines is thus critically important for ensuring the success of molecular breeding efforts. Here, we studied the genetic stability of resistance to insect pests and herbicides in transgenic rice lines at the molecular and phenotypic levels in a pesticide-free environment. Southern blot analysis, real-time polymerase chain reaction, and enzyme-linked immunosorbent assays revealed high stability in the copy numbers and expression levels of CRY1C, CRY2A, and BAR in transgenic lines across different generations, and gene expression levels were highly correlated with protein expression levels. The insecticide resistance of the transgenic rice lines was high. The larval mortality of Chilo suppressalis was 50.25% to 68.36% higher in transgenic lines than in non-transgenic control lines. Percent dead hearts and percent white spikelets were 16.66% to 22.15% and 27.07% to 33.47% lower in transgenic lines than in non-transgenic control lines, respectively. The herbicide resistance of the transgenic rice lines was also high. The bud length and root length ranged were 2.53 cm to 4.20 cm and 0.28 cm to 0.73 cm higher in transgenic lines than in non-transgenic control lines in the budding stage, respectively. Following application of the herbicide Basta, the chlorophyll content of the transgenic lines began to recover 2 d later in the seedling and tillering stages and 3 d later in the booting and heading stages, by contrast, the chlorophyll content of the non-transgenic lines did not recover and continued to decrease. These findings revealed high genetic stability of the resistance to insect pests and herbicides across several generations of transgenic rice regardless of the genetic background.

Expression of Pinellia pedatisecta Agglutinin PPA Gene in Transgenic Sugarcane Led to Stomata Patterning Change and Resistance to Sugarcane Woolly Aphid, Ceratovacuna lanigera Zehntner

The sugarcane woolly aphid is one of the main pests of sugarcane worldwide. The Pinellia pedatisecta agglutinin (PPA) gene has been demonstrated to function towards aphid resistance in other crops. In our study, in order to investigate the PPA function towards aphid control in sugarcane and its underlying mechanism, the PPA gene was overexpressed in a sugarcane Zhongzhe 1 (ZZ1) cultivar in independent transgenic sugarcane lines. It was confirmed in this study that PPA transgenic sugarcane can resist aphids via detecting the aphids’ development and tracing the survival number on PPA−transgenic sugarcane lines as well as PPA negative control lines. The mechanism of PPA lectin−associated defense against aphids was preliminarily explored. Stomatal patterning differences of sugarcane leaves between PPA−transgenic sugarcane lines and negative control lines were found. PPA overexpression led to an increase in stomata number and a decrease in stomata size that might have changed the transpiration status, which is critical for aphids’ passive feeding. Moreover, the antioxidant enzyme, sugar, tannin and chlorophyll content in sugarcane leaves before and after aphid infestation was determined. The results indicated that PPA overexpression in sugarcane resulted in an increase in antioxidant enzyme activity and tannin content, as well as a reduction in the decline of certain sugars. These together may improve sugarcane resistance against the sugarcane woolly aphid.

Silencing of Dicer-like protein 2a restores the resistance phenotype in the rice mutant, sxi4 (suppressor of Xa21-mediated immunity 4)

The rice immune receptor XA21 confers resistance to Xanthomonas oryzae pv. oryzae (Xoo), and upon recognition of the RaxX21-sY peptide produced by Xoo, XA21 activates the plant immune response. Here we screened 21 000 mutant plants expressing XA21 to identify components involved in this response, and reported here the identification of a rice mutant, sxi4, which is susceptible to Xoo. The sxi4 mutant carries a 32-kb translocation from chromosome 3 onto chromosome 7 and displays an elevated level of DCL2a transcript, encoding a Dicer-like protein. Silencing of DCL2a in the sxi4 genetic background restores resistance to Xoo. RaxX21-sY peptide-treated leaves of sxi4 retain the hallmarks of XA21-mediated immune response. However, WRKY45-1, a known negative regulator of rice resistance to Xoo, is induced in the sxi4 mutant in response to RaxX21-sY peptide treatment. A CRISPR knockout of a short interfering RNA (TE-siRNA815) in the intron of WRKY45-1 restores the resistance phenotype in sxi4. These results suggest a model where DCL2a accumulation negatively regulates XA21-mediated immunity by altering the processing of TE-siRNA815.

Analysis of expression characteristics of soybean leaf and root tissue-specific promoters in Arabidopsis and soybean

The characterization of tissue-specific promoters is critical for studying the functions of genes in a given tissue/organ. To study tissue-specific promoters in soybean, we screened tissue-specific expressed genes using published soybean RNA-Seq-based transcriptome data coupled with RT-PCR analysis. We cloned the promoters of three genes, GmADR1, GmBTP1, and GmGER1, and constructed their corresponding β-Glucuronidase (GUS) promoter-GUS reporter vectors. We generated transgenic Arabidopsis plants and examined the expression patterns of these promoters by GUS staining and RT-PCR analysis. We also transformed the promoter-GUS reporter vectors into soybean to obtain hairy roots, and examined promoter expression by GUS staining. We found a root-specific expression pattern of GmADR1 and GmBTP1 in both Arabidopsis and soybean, and the promoter of GmGER1 showed a leaf-specific pattern in transgenic Arabidopsis plants. To test the potential utility of these promoters in soybean improvement by transgenic means, we used the GmADR1 promoter to drive expression of a salt resistance gene in soybean, GmCaM4, by generating transgenic soybean plants. We found that the transgenic plants had significantly enhanced salt tolerance compared to non-transformed wild-type, suggesting that introducing endogenous promoters by transgenic means can drive the expression of functional genes in specific tissues and organs in soybean.

Production and characterization of the 13 C/15 N single-labeled insecticidal protein Cry1Ab/Ac using recombinant Escherichia coli

Synthetic Cry1Ab/Ac proteins expressed by genetically modified (GM) crops have a high potential to control insect pests without utilizing large amounts of chemical insecticides. Before these crops are used in agriculture, the environmental fate and interactions in the soil must be understood. Stable isotope-labeled Cry1Ab/Ac protein is a highly useful tool for collecting such data. We developed a protocol to produce ¹³ C/¹⁵ N single-labeled Cry proteins. The artificially synthesized gene Cry1Ab/Ac of Bt rice Huahui No. 1, which has been certified by the Chinese government to be safe for human consumption, was subcloned into pUC57, and the expression vector pET-28a-CryAb/Ac was constructed and transformed into Escherichia coli BL21 (DE3) competent cells. Next, 0.2 mM isopropyl thiogalactoside (IPTG) was added to these cells and cultured at 37°C for 4 h to induce the synthesis and formation of inclusion bodies in M9 growth media containing either [U-¹³ C] glucose (5% ¹³ C-enriched) or [¹⁵ N] ammonium chloride (5% ¹⁵ N-enriched). Then, Cry inclusion bodies were dissolved in urea and purified by affinity chromatography under denaturing conditions, renatured by dialysis, and further detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. The purities of ¹³ C/¹⁵ N-labeled Cry proteins reached 99% with amounts of 12.6 mg/L and 8.8 mg/L, respectively. The δ ¹³ C and ä ¹⁵ N values of ¹³ C-labeled Cry protein and ¹⁵ N-labeled Cry protein were 3,269‰ and 2,854‰, respectively. A bioassay test revealed that the labeled Cry1Ab/Ac proteins had strong insecticidal activity. The stable isotope-labeled insecticidal Cry proteins produced for the first time in this study will provide an experimental basis for future metabolic studies on Cry proteins in soil and the characteristics of nitrogen (N) and carbon (C) transformations. Our findings may also be employed as a reference for elucidating the environmental behavior and ecological effects of BT plants and expressed products.

Efficient Agrobacterium-mediated Transformation of The Elite-Indica Rice Variety Komboka

Genetic transformation is crucial for both investigating gene functions and for engineering of crops to introduce new traits. Rice (Oryza sativa L.) is an important model in plant research, since it is the staple food for more than half of the world's population. As a result, numerous transformation methods have been developed for both indica and japonica rice. Since breeders continuously develop new rice varieties, transformation protocols have to be adapted for each new variety. Here we provide an optimized transformation protocol with detailed tips and tricks for a new African variety Komboka using immature embryos. In Komboka, we obtained an apparent transformation rate of up to 48% for GUS/GFP reporter gene constructs using this optimized protocol. This protocol is also applicable for use with other elite indica rice varieties.

A new method for evaluating the effects of insecticidal proteins expressed by transgenic plants on ectoparasitoid of target pest

Transgenic Bt insect-resistant plants are highly resistant to Lepidoptera stockpile pest Indian meal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae), a storage pest. Habrobracon hebetor (Say) (Hymenoptera: Braconidae), which is an ectoparasitic wasp of Indian meal moth, may be exposed to the Bt protein through the food chain. In the current study, high dose of Cry1C protein was injected into the hemolymph of P. interpunctella by microinjection, and the hemolymph was used as the carrier to deliver Bt protein to the H. hebetor. Using this method, we developed a new Tier-1 risk assessment system for ectoparasitoid, successfully avoided "host/prey quality-mediated effect," and improve the accuracy of safety evaluation. Results showed that injected Cry1C was stable and bioactive in the hemolymph of P. interpunctella parasitized by H. hebetor, and high dose of Cry1C has no negative impacts on egg hatching rate, developmental duration from egg to adult, survival egg to adult, pupa weight, adults weight (male and female), adult longevity and reproduction, and activity of stress-related enzymes of H. hebetor. However, the hemolymph of P. interpunctella injected into Galanthus nivalis L. agglutinin (the positive control) had significant negative impact on these biological parameters of H. hebetor. The results indicate that H. hebetor are not sensitive to Cry1C protein at the tested concentration and there were no detrimental effects of Cry1C protein on any biological parameters tested in the present study. More importantly, we constructed a new efficient and simple system for the biosafety assessment on the larvae of ectoparasitoid of target pest.

Assessing the effects of Cry2Aa protein on Habrobracon hebetor (Hymenoptera: Braconidae), a parasitoid of Indian meal moth, Plodia interpunctella (lepidoptera: Pyralidae)

Transgenic crops express Cry proteins exhibit high resistant to target insect pests. When we evaluate the effects of Cry proteins on the parasitoid of target insect pest via tritrophic experiments (transgenic plant-target insect pest-parasitoid) host quality of parasitoids might decrease because of insecticidal protein ingestion, this would cause host-quality mediated effects and influence the accuracy of biosafety assessment. In the current study, high dose of Cry2Aa protein was injected into the hemolymph of Plodia interpunctella by microinjection, and the hemolymph was used as the carrier to deliver Cry protein to Habrobracon hebetor, which has been previously reported as an ectoparasitoid of P. interpunctella larval, in order to avoid the "host-quality mediated effects". Results showed that injected Cry2Aa remained at high concentration and bioactive in the hemolymph of P. interpunctella parasitized by H. hebetor, the hemolymph of P. interpunctella could be used as carriers of Cry protein to H. hebetor, and high dose of Cry2Aa have no negative impacts on the development time, weight of pupa, sex ratio, adults weight (male and female), adult longevity and fecundity, and the activity of stress-related enzymes of H. hebetor. However, the hemolymph of P. interpunctella injected into Galanthus nivalis agglutinin (the positive control) showed significant negative impact on these parameters measured in the present study of H. hebetor. This indicated that Cry2Aa protein had no detrimental effects on the biological parameters of H. hebetor measured in the current study. Meanwhile, this study provides a new method for the safety evaluation of the ectoparasitoids of target pest and might be expanded to the other species of ectoparasitoids of target insects of Cry proteins in biosafety risk assessment.

Effects of seed mixture sowing with transgenic Bt rice and its parental line on the population dynamics of target stemborers and leafrollers, and non-target planthoppers

The widespread planting of insect-resistant crops has caused a dramatic shift in agricultural landscapes, thus raising concerns about the potential impacts on both target and non-target pests. In this study, we examined the potential effects of intra-specific seed mixture sowing with transgenic Bt rice (Bt) and its parental non-transgenic line (Nt) (100% Bt rice [Bt₁₀₀ ], 5% Nt+95% Bt [Nt₀₅ Bt₉₅ ], 10% Nt+90% Bt [Nt₁₀ Bt₉₀ ], 20% Nt+80% Bt [Nt₂₀ Bt₈₀ ], 40% Nt+60% Bt [Nt₄₀ Bt₆₀ ] and 100% Nt rice [Nt₁₀₀ ]) on target and non-target pests in a 2-year field trial in southern China. The occurrence of target pests, Sesamia inferens, Chilo suppressalis and Cnaphalocrocis medinalis, decreased with the increased ratio of Bt rice, and the mixture ratios with more than 90% Bt rice (Bt₁₀₀ and Nt₀₅ Bt₉₅ ) significantly increased the pest suppression efficiency, with the lowest occurrences of non-target planthoppers, Nilaparvata lugens and Sogatella furcifera in Nt₁₀₀ and Nt₀₅ Bt₉₅ . Furthermore, there were no significant differences in 1000-grain dry weight and grain dry weight per 100 plants between Bt₁₀₀ and Nt₀₅ Bt₉₅ . Seed mixture sowing of Bt rice with ≤10% (especially 5%) of its parent line was sufficient to overcome potential compliance issues that exist with the use of block or structured refuge to provide most effective control of both target and non-target pests without compromising the grain yield. It is also expected that the strategy of seed mixture sowing with transgenic Bt rice and the non-transgenic parental line would provide rice yield stability while decreasing the insecticide use frequency in rice production.

Edit at will: Genotype independent plant transformation in the era of advanced genomics and genome editing

The combination of advanced genomics, genome editing and plant transformation biology presents a powerful platform for basic plant research and crop improvement. Together these advances provide the tools to identify genes as targets for direct editing as single base pair changes, deletions, insertions and site specific homologous recombination. Recent breakthrough technologies using morphogenic regulators in plant transformation creates the ability to introduce reagents specific toward their identified targets and recover stably transformed and/or edited plants which are genotype independent. These technologies enable the possibility to alter a trait in any variety, without genetic disruption which would require subsequent extensive breeding, but rather to deliver the same variety with one trait changed. Regulatory issues regarding this technology will predicate how broadly these technologies will be implemented. In addition, education will play a crucial role for positive public acceptance. Taken together these technologies comprise a platform for advanced breeding which is an imperative for future world food security.

Recent progress on the interaction between insects and Bacillus thuringiensis crops

Extensive use of chemical pesticides poses a great threat to the environment and food safety. The discovery of Bacillus thuringiensis (Bt) toxins with effective insecticidal activity against pests and the development of transgenic technology of plants opened a new era of pest control. Transgenic Bt crops, including maize, cotton and soya bean, have now been produced and commercialized to protect against about 30 major coleopteran and lepidopteran pests, greatly benefiting the environment and the economy. However, with the long-term cultivation of Bt crops, some target pests have gradually developed resistance. Numerous studies have indicated that mutations in genes for toxins activation, toxin-binding and insect immunization are important sources in Bt resistance. An in-depth exploration of the corresponding Bt-resistance mechanisms will aid in the design of new strategies to prevent and control pests. Future research will focus on Bt crops expressing new genes and multiple genes to control a broader range of pests as part of an integrated pest management programme. This article is part of the theme issue 'Biotic signalling sheds light on smart pest management'.

APOA-1Milano muteins, orally delivered via genetically modified rice, show anti-atherogenic and anti-inflammatory properties in vitro and in Apoe-/- atherosclerotic mice

BACKGROUND

Atherosclerosis is a slowly progressing, chronic multifactorial disease characterized by the accumulation of lipids, inflammatory cells, and fibrous tissue that drives to the formation of asymmetric focal thickenings in the tunica intima of large and mid-sized arteries. Despite the high therapeutic potential of ApoA-1 proteins, the purification and delivery into the disordered organisms of these drugs is still limited by low efficiency in these processes.

METHODS AND RESULTS

We report here a novel production and delivery system of anti-atherogenic APOA-1Milano muteins (APOA-1M) by means of genetically modified rice plants. APOA-1M, delivered as protein extracts from transgenic rice seeds, significantly reduced macrophage activation and foam cell formation in vitro in oxLDL-loaded THP-1 model. The APOA-1M delivery method and therapeutic efficacy was tested in healthy mice and in Apoe-/- mice fed with high cholesterol diet (Western Diet, WD). APOA-1M rice milk significantly reduced atherosclerotic plaque size and lipids composition in aortic sinus and aortic arch of WD-fed Apoe-/- mice as compared to wild type rice milk-treated, WD-fed Apoe-/- mice. APOA-1M rice milk also significantly reduced macrophage number in liver of WD-fed Apoe-/- mice as compared to WT rice milk treated mice.

TRANSLATIONAL IMPACT

The delivery of therapeutic APOA-1M full length proteins via oral administration of rice seeds protein extracts (the 'rice milk') to the disordered organism, without any need of purification, might overcome the main APOA1-based therapies' limitations and improve the use of this molecules as therapeutic agents for cardiovascular patients.

Impacts of elevated CO2 on exogenous Bacillus thuringiensis toxins and transgene expression in transgenic rice under different levels of nitrogen

Recent studies have highlighted great challenges of transgene silencing for transgenic plants facing climate change. In order to understand the impacts of elevated CO2 on exogenous Bacillus thuringiensis (Bt) toxins and transgene expression in transgenic rice under different levels of N-fertilizer supply, we investigated the biomass, exogenous Bt toxins, Bt-transgene expression and methylation status in Bt rice exposed to two levels of CO2 concentrations and nitrogen (N) supply (1/8, 1/4, 1/2, 1 and 2 N). It is elucidated that the increased levels of global atmospheric CO2 concentration will trigger up-regulation of Bt toxin expression in transgenic rice, especially with appropriate increase of N fertilizer supply, while, to some extent, the exogenous Bt-transgene expression is reduced at sub-N levels (1/4 and 1/2N), even though the total protein of plant tissues is reduced and the plant growth is restricted. The unpredictable and stochastic occurrence of transgene silencing and epigenetic alternations remains unresolved for most transgenic plants. It is expected that N fertilization supply may promote the expression of transgenic Bt toxin in transgenic Bt rice, particularly under elevated CO2.

Marker-free transgenic rice expressing the vegetative insecticidal protein (Vip) of Bacillus thuringiensis shows broad insecticidal properties

Genetically engineered rice lines with broad insecticidal properties against major lepidopteran pests were generated using a synthetic, truncated form of vegetative insecticidal protein (Syn vip3BR) from Bacillus thuringiensis. The selectable marker gene and the redundant transgene(s) were eliminated through Cre/ lox mediated recombination and genetic segregation to make consumer friendly Bt -rice. For sustainable resistance against lepidopteran insect pests, chloroplast targeted synthetic version of bioactive core component of a vegetative insecticidal protein (Syn vip3BR) of Bacillus thuringiensis was expressed in rice under the control of green-tissue specific ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit gene promoter. The transgenic plants (in Oryza sativa indica Swarna cultivar) showed high insect mortality rate in vitro against major rice pests, yellow stem borer (Scirpophaga incertulas), rice leaf folder (Cnaphalocrocis medinalis) and rice horn caterpillar (Melanitis leda ismene) in T1 generation, indicating insecticidal potency of Syn vip3BR. Under field conditions, the T1 plants showed considerable resistance against leaf folders and stem borers. The expression cassette (vip-lox-hpt-lox) as well as another vector with chimeric cre recombinase gene under constitutive rice ubiquitin1 gene promoter was designed for the elimination of selectable marker hygromycin phosphotransferase (hptII) gene. Crossing experiments were performed between T1 plants with single insertion site of vip-lox-hpt-lox T-DNA and one T1 plant with moderate expression of cre recombinase with linked bialaphos resistance (syn bar) gene. Marker gene excision was achieved in hybrids with up to 41.18 % recombination efficiency. Insect resistant transgenic lines, devoid of selectable marker and redundant transgene(s) (hptII + cre-syn bar), were established in subsequent generation through genetic segregation.

Molecular and functional characterization of cry1Ac transgenic pea lines

Transgenic pea lines transformed with the cry1Ac gene were characterized at molecular (PCR, RT-PCR, qRT-PCR and immunostrip assay) and functional levels (leaf paint and insect feeding bioassays). The results showed the presence, expression, inheritance and functionality of the introduced transgene at different progeny levels. Variation in the expression of the cry1Ac gene was observed among the different transgenic lines. In the insect bioassay studies using the larvae of Heliothis virescens, both larval survival and plant damage were highly affected on the different transgenic plants. Up to 100 % larval mortality was observed on the transgenic plants compared to 17.42 % on control plants. Most of the challenged transgenic plants showed very negligible to substantially reduced feeding damage indicating the insect resistance of the developed transgenic lines. Further analysis under field condition will be required to select promising lines for future uses.

Effects of Transgenic Bt Rice on Nontarget Rhopalosiphum maidis (Homoptera: Aphididae)

The effects of three transgenic Bacillus thuringiensis (Bt) rice lines, KMD1, KMD2, and G8-7, on biological parameters and population dynamics of nontarget insect, Rhopalosiphum maidis (Fitch) (Homoptera: Aphididae), were investigated in the laboratory and field. No significant differences were found between Bt and non-Bt rice lines for aphid survival. The developmental time of R. maidis that fed on KMD1 and KMD2 did not differ significantly from those of the individuals feeding on the parental variety Xiushui11, but significantly prolonged developmental time was observed on G8-7 as compared with its parental variety Xiushui110. Aphid fecundity was significantly higher on Bt than on parental rice. A 2-yr field survey indicated that Bt rice did not significantly affect the population dynamics of R. maidis in comparison with non-Bt rice. Additionally, guttation droplets of Bt rice and aphids feeding on Bt rice were analyzed for presence of Cry1Ab using ELISA. No Cry1Ab protein was found in aphid adults feeding on Bt rice lines both in the laboratory and field. By using the guttation droplets from the top of rice seedlings, we designed a novel method to collect phloem sap, and found that relatively low concentrations were detected in the guttation droplets from Bt rice lines. In conclusion, although the Bt rice lines tested in this study stimulate the fecundity of R. maidis, the aphid population density did not increase in Bt rice fields.

Principales promotores utilizados en la transformación genética de plantas

El conocimiento pleno de los promotores determina el éxito en la obtención de nuevos cultivares de plantas a través de técnicas biotecnológicas, ya que dicha secuencia del ADN regula la transcripción de otras regiones adyacentes o cercanas, encontrándose los siguientes promotores: constitutivos, tejido-específicos o estadio-específicos, inducibles y sintéticos. En esta revisión se resume de manera precisa los conceptos, ventajas y limitaciones de los distintos tipos de promotores, con ejemplos claros de ello.Palabras clave: promotor, biotecnología vegetal, transcripción genética.

Development of Marker-Free Insect-Resistant Indica Rice by Agrobacterium tumefaciens-Mediated Co-transformation

Agrobacterium-mediated co-transformation is an efficient strategy to generate marker-free transgenic plants. In this study, the vectors pMF-2A^∗ containing a synthetic cry2A^∗ gene driven by maize ubiquitin promoter and pCAMBIA1301 harboring hygromycin phosphotransferase gene (hpt) were introduced into Minghui86 (Oryza sativa L. ssp. indica), an elite indica restorer line. Two independent transformants containing both the cry2A^∗ gene and hpt gene were regenerated. Several homozygous marker-free transgenic progenies were derived from family 2AH2, and three of them were selected for further insect bioassay in the laboratory and field. Insect-resistance assays revealed that all the three transgenic lines were highly resistant to striped stem borer (Chilo suppressalis), yellow stem borer (Tryporyza incertulas) and rice leaf folder (Cnaphalocrocis medinalis). The measurement of Cry2A protein concentration showed that Cry2A protein was stably expressed in leaves and stems of homozygous transgenic lines and their hybrids. The yields of the marker-free homozygous transgenic lines and their hybrids were not significantly different from those of their corresponding controls. Furthermore, the results of flanking sequence isolation showed that the T-DNA in line 8-30 was integrated into the intergenic region of chromosome 2 (between Os02g43680 and Os02g43690). These results indicate that the marker-free transgenic rice has the potential for commercial production.

Development of photoperiod- and thermo-sensitive male sterility rice expressing transgene Bacillus thuringiensis

Stem borers and leaffolders are the main pests that cause severe damage in rice (Oryza sativa L.) production worldwide. We developed the first photoperiod- and thermo-sensitive male sterility (PTSMS) rice 208S with the cry1Ab/1Ac Bacillus thuringiensis (Bt) gene, through sexual crossing with Huahui 1 (elite line with the cry1Ab/1Ac gene). The novel 208S and its hybrids presented high and stable resistance to stem borers and leaffolders, and the content of Cry1Ab/1Ac protein in chlorophyllous tissues achieved the identical level as donor and showed little accumulation in non-chlorophyllous tissue. No dominant dosage effect in the Bt gene was observed in 208S and its derived hybrids. An analysis of fertility transition traits indicated that 208S was completely sterile under long day length/high temperature, but partially fertile under short day length/low temperature. With fine grain quality and favorable combining ability, 208S had no observed negative effects on fertility and agronomic traits from Bt (cry1Ab/1Ac). Additionally, 208S as a male sterile line showed no fertility decrease caused by Bt transgenic process, as it is the case in Huahui 1. Thus, 208S has great application value in two-line hybrid production for insect resistance, and can also be used as a bridge material in rice Bt transgenic breeding.

Bt rice expressing Cry2Aa does not harm Cyrtorhinus lividipennis, a main predator of the nontarget herbivore Nilapavarta lugens

T2A-1 is a newly developed transgenic rice that expresses a synthesized cry2Aa gene driven by the maize ubiquitin promoter. T2A-1 exhibits high resistance against lepidopteran pests of rice. The brown planthopper, Nilapavarta lugens (Stål), is a main nontarget sap-sucking insect pest of rice, and Cyrtorhinus lividipennis (Reuter) is the major predator of the eggs and young nymphs of planthoppers. As C. lividipennis may expose to the Cry2Aa protein via N. lugens, it is therefore essential to assess the potential effects of transgenic cry2Aa rice on this predator. In the present study, three experiments were conducted to evaluate the ecological risk of transgenic cry2Aa rice to C. lividipennis: (1) a direct feeding experiment in which C. lividipennis was fed an artificial diet containing Cry2Aa at the dose of 10-time higher than that it may encounter in the realistic field condition; (2) a tritrophic experiment in which the Cry2Aa protein was delivered to C. lividipennis indirectly through prey eggs or nymphs; (3) a realistic field experiment in which the population dynamics of C. lividipennis were investigated using vacuum-suction. Both direct exposure to elevated doses of the Cry2Aa protein and prey-mediated exposure to realistic doses of the protein did not result in significant detrimental effects on the development, survival, female ratio and body weight of C. lividipennis. No significant differences in population density and population dynamics were observed between C. lividipennis in transgenic cry2Aa and nontransgenic rice fields. It may be concluded that transgenic cry2Aa rice had no detrimental effects on C. lividipennis. This study represents the first report of an assessment continuum for the effects of transgenic cry2Aa rice on C. lividipennis.

A Novel Moderate Constitutive Promoter Derived from Poplar (Populus tomentosa Carrière)

A novel sequence that functions as a promoter element for moderate constitutive expression of transgenes, designated as the PtMCP promoter, was isolated from the woody perennial Populus tomentosa. The PtMCP promoter was fused to the GUS reporter gene to characterize its expression pattern in different species. In stable Arabidopsis transformants, transcripts of the GUS reporter gene could be detected by RT-PCR in the root, stem, leaf, flower and silique. Further histochemical and fluorometric GUS activity assays demonstrated that the promoter could direct transgene expression in all tissues and organs, including roots, stems, rosette leaves, cauline leaves and flowers of seedlings and maturing plants. Its constitutive expression pattern was similar to that of the CaMV35S promoter, but the level of GUS activity was significantly lower than in CaMV35S promoter::GUS plants. We also characterized the promoter through transient expression in transgenic tobacco and observed similar expression patterns. Histochemical GUS staining and quantitative analysis detected GUS activity in all tissues and organs of tobacco, including roots, stems, leaves, flower buds and flowers, but GUS activity in PtMCP promoter::GUS plants was significantly lower than in CaMV35S promoter::GUS plants. Our results suggested that the PtMCP promoter from poplar is a constitutive promoter with moderate activity and that its function is presumably conserved in different species. Therefore, the PtMCP promoter may provide a practical choice to direct moderate level constitutive expression of transgenes and could be a valuable new tool in plant genetic engineering.

Marker-free, tissue-specific expression of Cry1Ab as a safe transgenic strategy for insect resistance in rice plants

BACKGROUND

Rice is the major food resource for nearly half of the global population; however, insect infestation could severely affect the production of this staple food. To improve rice insect resistance and reduce the levels of Bt toxin released into the environment, the Cry1Ab gene was conjugated to the rice rbcS promoter to express Bt toxin in specific tissues of transgenic plants.

RESULTS

Eight marker-free, T(2) lines were separated from the T(0) cotransformants. Using RT-PCR, high levels of Cry1Ab expression were detected in the leaf but not in the seed. The Cry1Ab protein level ranged from 1.66 to 3.31 µg g(-1) in the leaves of four transgenic lines, but was barely detectable in their seeds by ELISA. Bioassays showed that the mortality rate of silkworm larvae feeding on mulberry leaves dipped in transgenic rice flour and pollen was less than that of the positive control (KMD), and that their average weight was higher than that of KMD, suggesting that the Cry1Ab protein was not expressed in the seed and pollen.

CONCLUSION

The transgene conferred a high level of resistance to insects and biosafety to the rice plants, which could be directly used in rice breeding.

Molecular strategies to engineer transgenic rice seed compartments for large-scale production of plant-made pharmaceuticals

The use of plants as bioreactors for the large-scale production of recombinant proteins has emerged as an exciting area of research. The current shortages in protein therapeutics due to the capacity and economic bottlenecks faced with modern protein production platforms (microbial, yeast, mammalian) has driven considerable attention towards molecular pharming. Utilizing plants for the large-scale production of recombinant proteins is estimated to be 2-10% the cost of microbial platforms, and up to 1,000-fold more cost effective than mammalian platforms (Twyman et al. Trends Biotechnol 21:570-578, 2003; Sharma and Sharma, Biotechnol Adv 27:811-832, 2009). In order to achieve an economically feasible plant production host, protein expression and accumulation must be optimized. The seed, and more specifically the rice seed has emerged as an ideal candidate in molecular pharming due to its low protease activity, low water content, stable protein storage environment, relatively high biomass, and the molecular tools available for manipulation (Lau and Sun, Biotechnol Adv 27:1015-1022, 2009).

A 90-day dietary toxicity study of genetically modified rice T1C-1 expressing Cry1C protein in Sprague Dawley rats

In a 90-day study, Sprague Dawley rats were fed transgenic T1C-1 rice expressing Cry1C protein and were compared with rats fed non-transgenic parental rice Minghui 63 and rats fed a basal diet. No adverse effects on animal behavior or weight gain were observed during the study. Blood samples were collected and analyzed, and standard hematological and biochemical parameters were compared. A few of these parameters were found to be significantly different, but were within the normal reference intervals for rats of this breed and age, and were thus not considered to be treatment-related. Following sacrifice, a large number of organs were weighed, and macroscopic and histopathological examinations were performed with no changes reported. The aim of this study was to use a known animal model to determine the safety of the genetically modified (GM) rice T1C-1. The results showed no adverse or toxic effects due to T1C-1 rice when tested in this 90-day study.

Differentially expressed genes distributed over chromosomes and implicated in certain biological processes for site insertion genetically modified rice Kemingdao

Release of genetically modified (GM) plants has sparked off intensive debates worldwide partly because of concerns about potential adverse unintended effects of GM plants to the agro system and the safety of foods. In this study, with the aim of revealing the molecular basis for unintended effects of a single site insertion GM Kemingdao (KMD) rice transformed with a synthetic cry1Ab gene, and bridging unintended effects of KMD rice through clues of differentially expressed genes, comparative transcriptome analyses were performed for GM KMD rice and its parent rice of Xiushui11 (XS11). The results showed that 680 differentially expressed transcripts were identified from 30-day old seedlings of GM KMD rice. The absolute majority of these changed expression transcripts dispersed and located over all rice chromosomes, and existed physical distance on chromosome from the insertion site, while only two transcripts were found to be differentially expressed within the 21 genes located within 100 kb up and down-stream of the insertion site. Pathway and biology function analyses further revealed that differentially expressed transcripts of KMD rice were involved in certain biological processes, and mainly implicated in two types of pathways. One type was pathways implicated in plant stress/defense responses, which were considerably in coordination with the reported unintended effects of KMD rice, which were more susceptible to rice diseases compared to its parent rice XS11; the other type was pathways associated with amino acids metabolism. With this clue, new unintended effects for changes in amino acids synthesis of KMD rice leaves were successfully revealed. Such that an actual case was firstly provided for identification of unintended effects in GM plants by comparative transciptome analysis.

Expression of the nos operon proteins from Pseudomonas stutzeri in transgenic plants to assemble nitrous oxide reductase

Nitrous oxide (N(2)O) is a stable greenhouse gas that plays a significant role in the destruction of the ozone layer. Soils are a significant source of atmospheric N(2)O. It is important to explore some innovative and effective biology-based strategies for N(2)O mitigation. The enzyme nitrous oxide reductase (N(2)OR), naturally found in soil bacteria, is responsible for catalysing the final step of the denitrification pathway, conversion of N(2)O to dintrogen gas (N(2)). To transfer this catalytic pathway from soil into plants and amplify the abundance of this essential mechanism (to reduce global warming), a mega-cassette of five coding sequences was assembled to produce transgenic plants heterologously expressing the bacterial nos operon in plant leaves. Both the single-gene transformants (nosZ) and the multi-gene transformants (nosFLZDY) produced active recombinant N(2)OR. Enzymatic activity was detected using the methyl viologen-linked enzyme assay, showing that extracts from both types of transgenic plants exhibited N(2)O-reducing activity. Remarkably, the single-gene strategy produced higher reductase capability than the whole-operon approach. The data indicate that bacterial N(2)OR expressed in plants could convert N(2)O into inert N(2) without involvement of other Nos proteins. Silencing by homologous signal sequences, or cryptic intracellular targeting are possible explanations for the low activities obtained. Expressing N(2)OR from Pseudomonas stutzeri in single-gene transgenic plants indicated that such ag-biotech solutions to climate change have the potential to be easily incorporated into existing genetically modified organism seed germplasm.

[Molecular characteristics and specific PCR detection of transgenic rice containing Cry1Ab]

Bt01 is a new type of rice that has been genetically modified to express Cry1Abprotein. This study confirmed that Cry1Abwas inserted into Bt01 as a single copy using Southern blotting analysis. TAIL-PCR method was further used to obtain its insertion site information. Specific PCR primers and TaqMan probes were designed based on the 5'-integration junction sequence of transgenic rice Bt01. The results showed that the limit of detection (LOD) was ten copies in qualitative PCR. The quantitative PCR assay showed that the LOD was five copies, and the limit of quantification (LOQ) was ten cop-ies. In addition, the accuracy of the established quantitative PCR was verified by detecting two samples containing 3% and 0.5%Bt01, respectively. The quantitative PCR analysis showed the results were 2.7% and 0.47%, respectively.The above results indicated that the event-specific PCR methods developed have high specificity and good sensitivity, which could be effective methods for identifying and testing the genetically modified Bt01 rice.

Field evaluation of effects of transgenic cry1Ab/cry1Ac, cry1C and cry2A rice on Cnaphalocrocis medinalis and its arthropod predators

The impacts of transgenic Bt rice on target pests and their predators need to be clarified prior to the commercialization of Bt rice. In this study, the percentages of folded leaves of three transgenic Bt rice lines and non-transgenic parental rice line caused by Cnaphalocrocis medinalis were studied over two successive growing seasons. In addition, the population densities, relative abundance and population dynamics of C. medinalis and four species of its natural arthropod predators were investigated at three sites in China. The results showed that rice line significantly affected the percentages of folded leaves and population densities of C. medinalis larvae. Significantly higher percentages of folded leaves were observed on the non-transgenic rice compared with the three transgenic Bt rice on most sampling dates. Significantly higher densities of C. medinalis larvae and higher relative abundance of C. medinalis within phytophages were found on non-transgenic rice compared with three transgenic Bt rice at different sites across the study period. The population dynamics of C. medinalis larvae were significantly affected by rice line, rice line×sampling date, rice line×year, rice line×sampling date×year. However, there was little, if any, significant difference in the relative abundance, population density and population dynamics of the four arthropod predators between the three Bt rice lines and non-transgenic rice. The results of this study indicate that the Bt toxin in transgenic Bt rice can effectively suppress the occurrence of C. medinalis, but has no significant effects on the occurrence of the four predatory arthropod species.

Agrobacterium-mediated transformation of leaf base derived callus tissues of popular indica rice (Oryza sativa L. sub sp. indica cv. ADT 43)

A simple and efficient protocol for the Agrobacterium-mediated transformation of an agronomically useful abiotic sensitive popular indica rice cv. ADT 43 has been developed. Initiation of calli were best achieved from the leaf bases of 4 days old rice seedlings on LS medium supplemented with 2.5mg/L 2,4-D and 1.0mg/L thiamine-HCl. Rice calli immersed in Agrobacterium suspension (strain EHA 105, OD(600)=0.8) were co-cultured on LS30-AsPC medium for 2 days at 25±2°C in the dark. Based on GUS expression analysis, 10min co-cultivation time with 100μM acetosyringone was found optimum for the delivery of gus gene. Calli were proved to be very sensitive to Agrobacterium infection and we found that the level of necrotic response can be minimized after co-cultivation with 30% LS, 10g/L PVP, 10% coconut water and 250mg/L timentin which improved the final transformation efficiency to 9.33%. Molecular and genetic analysis of transgenic plants reveals the integration, expression and inheritance of transgene in the progeny (T(1)) of these plants. The copy number of transgenes has been found to vary from 1 to 2 in transgenic plants (T(0) and T(1)).

Agrobacterium-mediated transformation of Australian rice varieties and promoter analysis of major pollen allergen gene, Ory s 1

A simple protocol for Agrobacterium-mediated transformation of Australian rice using mature embryos is described. Transgenic plants of two commercial genotypes of Australian rice, Amaroo and Millin, were produced. Transgenic plants were obtained by applying selection pressure to callus and to the regenerated shoots. Exclusion of the selective agent (hygromycin) during plant regeneration was found to be critical for recovery of transgenic plants from these commercial varieties. Transgenic plants were produced after 3 months. The developed system was also used to study spatial and temporal expression of a rice pollen-specific gene, Ory s 1. Expression of pOry s 1::uidA in transgenic rice demonstrated GUS expression in mature pollen, hence indicating potential use of this promoter to direct pollen-specific gene expression. Further Ory s 1 5' deletion study indicated that the pollen-specificity element may reside within -405 bp to the start of the transcription, while the region upstream of -405 contained a cis-acting regulatory element(s) responsible for quantitative expression of this gene.

[Effect of transgenic insect-resistant rice on biodiversity]

Rice is the most important food crops in maintaining food security in China. The loss of China's annual rice production caused by pests is over ten million tons. Present studies showed that the transgenic insect-resistant rice can substantially reduce the application amount of chemical pesticides. In the case of no pesticide use, the pest density in transgenic rice field is significantly lower than that in non-transgenic field, and the neutral insects and natural enemies of pests increased significantly, indicating that the ecological environment and biodiversity toward the positive direction. The gene flow frequency from transgenic rice is dramatically reduced with the distance increases, reaching less than 0.01% at the distance of 6.2 m. Application of transgenic insect-resistant rice in China has an important significance for ensuring food security, maintaining sustainable agricultural development, and protecting the ecological environment and biodiversity. This review summarized the research progress in transgenic insect-resistant rice and its effect on biodiversity. The research directions and development trends of crop pest controlling in future are discussed. These help to promote better use of transgenic insect-resistant rice.

Evaluating the non-rice host plant species of Sesamia inferens (Lepidoptera: Noctuidae) as natural refuges: resistance management of Bt rice

Although rice (Oryza sativa L.) lines that express Bacillus thuringiensis (Bt) toxins have shown great potential for managing the major Lepidoptera pests of rice in southern China, including Sesamia inferens, their long-term use is dependent on managing resistance development to Bt toxins in pest populations. The maintenance of "natural" refuges, non-Bt expressing plants that are hosts for a target pest, has been proposed as a means to minimize the evolution of resistance to Bt toxins in transgenic plants. In the current study, field surveys and greenhouse experiments were conducted to identify host plants of S. inferens that could serve as "natural" refuges in rice growing areas of southern China. A field survey showed that 34 plant species in four families can be alternative host plants of S. inferens. Based on injury level under field conditions, rice (Oryza sativa L.); water oat (Zizania latifolia Griseb.); corn (Zea mays L.); tidalmarsh flatsedge (Cyperus serotinus Rottb.); and narrow-leaved cat-tail (Typha angustifolia Linn.) were identified as the primary host plant species of S. inferens. Greenhouse experiments further demonstrated that water oat, corn, and narrow-leaved cat-tail could support the survival and development of S. inferens. Interestingly, greenhouse experiments showed that S. inferens preferred to lay eggs on tidalmarsh flatsedge compared with the other three nonrice host species, although no pupae were found in the plants examined in field surveys. Few larvae were found to survive on tidalmarsh flatsedge in greenhouse bioassays, suggesting that tidalmarsh flatsedge could serve as a "dead-end" trap crop for S. inferens, but is not a candidate to serve as natural refuge to maintain susceptible S. inferens. Overall, these results suggest that water-oat, corn, and narrow-leaved cat-tail might serve as "natural refuge" for S. inferens in rice planting area of southern China when Bt rice varieties are planted.

A mini review: RuBisCo small subunit as a strong, green tissue-specific promoter

Plant genetic transformation is a powerful application used to study gene expression in plants. Transcriptomics has the potential to rapidly increase our knowledge of spatial and temporal gene expression and lead to new promoters for research and development. The availability of a broad spectrum of promoters with the ability to regulate the temporal and spatial expression patterns of transgenes can increase the successful application of transgenic technology. A variety of promoters is necessary at all levels of genetic engineering in plants, from basic research, to the development of economically viable crops and plant commodities, it can address legitimate concerns raised about the safety and containment of transgenic plants in the environment. Compared with temporal- or spatial-specific expression of a toxin, constitutive expression of foreign proteins in transgenic plants can cause adverse effects. The constitutive overexpression of transgenes that interferes with normal processes in a plant underscores the need for refinement of transgene expression. The development of tissue-specific promoters to drive transgene expression has helped fulfill that need. Therefore, in certain circumstances it is desirable to use expression-specific promoters which only express the foreign gene in specific plant tissues or organs. This review highlights the uses and benefits reaped by the use of green tissue-specific promoter for the RuBisCo small subunit in different crops and systems and thus establishing a broad range of tissue-specific promoters. Such plant promoters that are activated precisely when and where they are needed would be ideal for genetic engineering strategies.

Multi-generation effects of Bt rice on Anagrus nilaparvatae, a parasitoid of the nontarget pest Nilapavarta lugens

Little is known about the potential cumulative long-term effects of transgenic crops on nontarget organisms. In the present laboratory study, the potential cumulative effects of transgenic Bacillus thuringiensis (Bt) rice on parasitoids in successive generations were observed for an egg parasitoid, Anagrus nilaparvatae parasitizing eggs of Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) feeding on Bt rice. Enzyme-linked immunosorbent assay test confirmed that Cry1Ab insecticidal protein could be detected in newly eclosed parasitoid adults. However, no significant effect on the fecundity of Anagrus nilaparvatae Pang et Wang (Hymenoptera: Mymaridae) was observed between Bt and non-Bt rice. Developmental times of both genders of A. nilaparvatae parasitizing host eggs laid in Bt (KMD1 and KMD2) rice lines were significantly prolonged from first generation to second generation, but not always prolonged from third generation to 11th generation as compared with the control rice line. Furthermore, the sex ratio of A. nilaparvatae progeny from the first generation to 11th generation in three rice lines was not significantly different. In general, our results suggested that the effect of Bt rice on this parasitoid could be negligible.

Production of marker-free transgenic rice expressing tissue-specific Bt gene

The hybrid Bacillus thuringiensis (Bt) δ-endotoxin gene Cry1Ab/Ac was used to develop a transgenic Bt rice (Oryza sativa L.) targeting lepidopteran insects of rice. Here, we show the production of a marker-free and tissue-specific expressing transgenic Bt rice line L24 using Agrobacterium-mediated transformation and a chemically regulated, Cre/loxP-mediated DNA recombination system. L24 carries a single copy of marker-free T-DNA that contains the Cry1Ab/Ac gene driven by a maize phosphoenolpyruvate carboxylase (PEPC) gene promoter. The marker-free T-DNA was integrated into the 3' untranslated region of rice gene Os01g0154500 on the short arm of chromosome 1. Compared to the constitutive and non-specific expression of the P (Actin1):Cry1Ab/Ac:T (Nos) gene in the control Bt rice line T51-1, the P ( Pepc ):Cry1Ab/Ac:T (Nos ) gene was detected only in the leaf and stem tissues of L24. More importantly, compared to high levels of CRY1Ab/Ac proteins accumulated in T51-1 seeds, the CRY1Ab/Ac proteins were not detectable in L24 seeds by Western blot analysis. As demonstrated by insect bioassay, L24 provided similar level of resistance to rice leaffolder (Cnaphalocrocis medinalis) as T51-1. The marker-free transgenic line L24 can be used directly in rice breeding for insect resistance to lepidopteran insects where absence of Bt toxin protein in the seed is highly desirable.

Transformation of coffee (Coffea Arabica L. cv. Catimor) with the cry1ac gene by biolistic, without the use of markers

The transformation of coffee plantlets with the cry1ac gene of Bacillus thuringiensis was achieved by biolistic using either the whole pUBC plasmid or only the ubi-cry1ac-nos genetic cassette. The cry1ac gene was inserted into coffee plants in order to confer resistance to the leaf miner Leucoptera coffeella, an insect responsible for considerable losses in coffee crops. Bearing in mind that the genetic cassettes used for this study lack reporter genes and/or selection marker genes, the parameters for the transformation procedure by biolistic were previously standardised with a plasmid carrying the gus reporter gene. The presence of the cry1ac gene in young plantlet tissues was determined by PCR, Southern blot and reverse transcription-PCR. Our results show that the obtainment of viable coffee plantlets, transformed by bombardment with the cry1ac gene and without selection markers nor reporter genes, is feasible.

Transgenic rice plants expressing a modified cry1Ca1 gene are resistant to Spodoptera litura and Chilo suppressalis

Nucleotide sequence encoding the truncated insecticidal Cry1Ca1 protein from Bacillus thuringiensis was extensively modified based on the codon usage of rice genes. The overall G + C contents of the synthetic cry1Ca1 coding sequence were raised to 65% with an additional bias of enriching for G and C ending codons as preferred by monocots. The synthetic gene was introduced into the Chinese japonica variety, Xiushui 11, by Agrobacterium-mediated transformation. Transgenic rice plants harboring this gene were highly resistant to Chilo suppressalis and Spodoptera litura larvae as revealed by insect bioassays. High levels of Cry1Ca1 protein were obtained in the leaves of transgenic rice, which were effective in achieving 100% mortality of S. litura and C. suppressalis larvae. The levels of Cry1Ca1 expression in the leaves of these transgenic plants were up to 0.34% of the total soluble proteins. The larvae of C. suppressalis and S. litura could consume a maximum of 1.89 and 4.89 mm2 of transgenic leaf area whereas the consumption of nontransgenic leaves by these larvae was significantly higher; 58.33 and 61.22 mm2, respectively. Analysis of R1 transgenic plants indicated that the cry1Ca1 was inherited by the progeny plants and provided complete protection against C. suppressalis and S. litura larvae.

Isolation and characterization of oil palm constitutive promoter derived from ubiquitin extension protein (uep1) gene

The ubiquitin extension protein (uep1) gene was identified as a constitutively expressed gene in oil palm. We have isolated and characterized the 5' region of the oil palm uep1 gene, which contains an 828 bp sequence upstream of the uep1 translational start site. Construction of a pUEP1 transformation vector, which contains gusA reporter gene under the control of uep1 promoter, was carried out for functional analysis of the promoter through transient expression studies. It was found that the 5' region of uep1 functions as a constitutive promoter in oil palm and could drive GUS expression in all tissues tested, including embryogenic calli, embryoid, immature embryo, young leaflet from mature palm, green leaf, mesocarp and meristematic tissues (shoot tip). This promoter could also be used in dicot systems as it was demonstrated to be capable of driving gusA gene expression in tobacco.

Effects of transgenic rice expressing Bacillus thuringiensis Cry1Ab protein on ground-dwelling collembolan community in postharvest seasons

During 2005-2008, field studies were conducted at two locations in Chongqing, China, to assess the potential effects of transgenic rice expressing Bacillus thuringiensis (Bt) Cry1Ab protein on the nontarget ground-dwelling collembolan community in three postharvest seasons. Collembolans in non-Bt and Bt rice fields were sampled with pitfall traps during each of two postharvest seasons of 2005/2006 and 2006/2007 and litterbag traps during each of three postharvest seasons of 2005/2006, 2006/2007, and 2007/2008. Ground-dwelling collembolans in rice fields during the postharvest seasons were abundant, whereas community densities varied considerably between the two locations and among the three seasons. A total of 67,310 collembolans, representing three species, Entomobrya griseoolivata, Hypogastrura matura, and Bourletiella christianseni, were captured during the three postharvest seasons. E. griseoolivata was the predominant species, accounting for 87.7% of the total captures, followed by H. matura (10.7%) and B. christianseni (1.6%). In general, there were no significant differences in species compositions and abundances of each species between Bt and non-Bt paddy fields, suggesting no significantly impact of plant residues of Cry1Ab rice on collembolan communities during postharvest seasons.