Gossypol and related compounds are produced and accumulate in the aboveground parts of the cotton plant, independent of roots as the source

Use of Ultra-low gossypol cottonseed event as a scion in a graft combination confirmed that roots are not a source of terpenoids in the aboveground parts of a cotton plant. Gossypol and related terpenoids, derived from the same basic biosynthetic pathway, are present in the numerous lysigenous glands in the aboveground parts of a cotton plant. Roots, with sparse presence of such glands, do produce significant amount of gossypol and a different set of terpenoids. These compounds serve a defensive function against various pests and pathogens. This investigation was undertaken to examine whether gossypol produced in the roots can replenish the gossypol content of the cottonseed-glands that are largely devoid of this terpenoid in a genetically engineered event. Graft unions between a scion derived from the RNAi-based, Ultra-low gossypol cottonseed (ULGCS) event, TAM66274, and a rootstock derived from wild-type parental genotype, Coker 312 (Coker), were compared with various other grafts that served as controls. The results showed that the seeds developing within the scion of test grafts (ULGCS/Coker) continued to maintain the ultra-low gossypol levels found in the TAM66274 seeds. Molecular analyses confirmed that while the key gene involved in gland development showed normal activity in the developing embryos in the scion, two genes encoding the enzymes involved in gossypol biosynthesis were suppressed. Thus, the gene expression data confirmed the results obtained from biochemical measurements and collectively demonstrated that roots are not a source of gossypol for the aboveground parts of the cotton plant. These findings, combined with the results from previous investigations, support the assertion that gossypol and related terpenoids are produced in a highly localized manner in various organs of the cotton plant and are retained therein.

Clinical and Radiological Study of Serum Fluoride in Relation to Knee Osteoarthritis

Introduction

Fluorosis has been associated with an increased risk of degenerative changes in the knee. Multiple studies have found an association between arthritis and elevated fluoride levels. We aim to delineate if elevated fluoride level has any direct correlation with the degree of radiological grading and clinical symptoms in knee arthritis.

Materials and Methods

A cross-sectional study of 80 knee arthritis patients was conducted from February 2017 to April 2018. Serum fluoride levels were measured and patient's pain scores, WOMAC scores and radiological grading were correlated with the elevated fluoride levels.

Results

In our study, 30 out of 80 patients had increased serum fluoride level. Statistically significant differences were noted in VAS score, WOMAC score and Kellgren and Lawrence radiological grades between patients with normal serum fluoride level and those with elevated fluoride level.

Conclusion

There is an increased risk of knee arthritis in patients with elevated blood fluoride levels and patients with increased fluoride levels are associated with more severe symptoms and radiographic disease.

Constitutive and induced insect resistance in RNAi-mediated ultra-low gossypol cottonseed cotton

BACKGROUND

Besides fibers, cotton plants also produce a large amount of seeds with a high oil and protein content. The use of these seeds is restricted by their high contents of the terpenoid gossypol, which is harmful to humans and livestock. Using a genetic engineering approach, "Ultra-low gossypol cottonseed" (ULGCS) plants were produced by knocking down an enzyme that catalyzes the formation of a precursor of gossypol. This was accomplished via RNAi-mediated silencing of the target gene using a seed-specific α-globulin promotor. Since gossypol is also a crucial defense mechanism against leaf-feeding herbivores, ULGCS plants might possess lower herbivore resistance than non-engineered plants. Therefore, we tested the constitutive and inducible direct insect resistance of two ULGCS cotton lines against the African cotton leafworm, Spodoptera littoralis.

RESULT

The herbivore was equally affected by both ULGCS lines and the control (Coker 312) line when feeding on fully expanded true leaves from undamaged plants and plants induced by jasmonic acid. When plants were induced by caterpillar-damage, however, S. littoralis larvae performed better on the ULGCS plants. Terpenoid analyses revealed that the ULGCS lines were equally inducible as the control plants. Levels of terpenoids were always lower in one of the two lines. In the case of cotyledons, caterpillars performed better on ULGCS cotton than on conventional cotton. This was likely caused by reduced levels of gossypol in ULGCS cotyledons.

CONCLUSION

Despite those effects, the insect resistance of ULGSC cotton can be considered as largely intact and the plants may, therefore, be an interesting alternative to conventional cotton varieties.

Genes regulating gland development in the cotton plant

In seeds and other parts of cultivated, tetraploid cotton (Gossypium hirsutum L.), multicellular groups of cells lysigenously form dark glands containing toxic terpenoids such as gossypol that defend the plant against pests and pathogens. Using RNA-seq analysis of embryos from near-isogenic glanded (Gl2 Gl2 Gl3 Gl3 ) versus glandless (gl2 gl2 gl3 gl3 ) plants, we identified 33 genes that expressed exclusively or at higher levels in embryos just prior to gland formation in glanded plants. Virus-induced gene silencing against three gene pairs led to significant reductions in the number of glands in the leaves, and significantly lower levels of gossypol and related terpenoids. These genes encode transcription factors and have been designated the 'Cotton Gland Formation' (CGF) genes. No sequence differences were found between glanded and glandless cotton for CGF1 and CGF2 gene pairs. The glandless cotton has a transposon insertion within the coding sequence of the GoPGF (synonym CGF3) gene of the A subgenome and extensive mutations in the promoter of D subgenome homeolog. Overexpression of GoPGF (synonym CGF3) led to a dramatic increase in gossypol and related terpenoids in cultured cells, whereas CRISPR/Cas9 knockout of GoPGF (synonym CGF3) genes resulted in glandless phenotype. Taken collectively, the results show that the GoPGF (synonym CGF3) gene plays a critical role in the formation of glands in the cotton plant. Seed-specific silencing of CGF genes, either individually or in combination, could eliminate glands, thus gossypol, from the cottonseed to render it safe as food or feed for monogastrics.

ptxD gene in combination with phosphite serves as a highly effective selection system to generate transgenic cotton (Gossypium hirsutum L.)

This report demonstrates the usefulness of ptxD/phosphite as a selection system that not only provides a highly efficient and simple means to generate transgenic cotton plants, but also helps address many of the concerns related to the use of antibiotic and herbicide resistance genes in the production of transgenic crops. Two of the most popular dominant selectable marker systems for plant transformation are based on either antibiotic or herbicide resistance genes. Due to concerns regarding their safety and in order to stack multiple traits in a single plant, there is a need for alternative selectable marker genes. The ptxD gene, derived from Pseudomonas stutzeri WM88, that confers to cells the ability to convert phosphite (Phi) into orthophosphate (Pi) offers an alternative selectable marker gene as demonstrated for tobacco and maize. Here, we show that the ptxD gene in combination with a protocol based on selection medium containing Phi, as the sole source of phosphorus (P), can serve as an effective and efficient system to select for transformed cells and generate transgenic cotton plants. Fluorescence microscopy examination of the cultures under selection and molecular analyses on the regenerated plants demonstrate the efficacy of the system in recovering cotton transformants following Agrobacterium-mediated transformation. Under the ptxD/Phi selection, an average of 3.43 transgenic events per 100 infected explants were recovered as opposed to only 0.41% recovery when bar/phosphinothricin (PPT) selection was used. The event recovery rates for nptII/kanamycin and hpt/hygromycin systems were 2.88 and 2.47%, respectively. Molecular analysis on regenerated events showed a selection efficiency of ~ 97% under the ptxD/Phi system. Thus, ptxD/Phi has proven to be a very efficient, positive selection system for the generation of transgenic cotton plants with equal or higher transformation efficiencies compared to the commonly used, negative selection systems.

CRISPR/Cas9-mediated targeted mutagenesis in upland cotton (Gossypium hirsutum L.)

The clustered, regularly interspaced, short palindromic repeats (CRISPR)/CRISPR associated (Cas)9 protein system has emerged as a simple and efficient tool for genome editing in eukaryotic cells. It has been shown to be functional in several crop species, yet there are no reports on the application of this or any other genome editing technologies in the cotton plant. Cotton is an important crop that is grown mainly for its fiber, but its seed also serves as a useful source of edible oil and feed protein. Most of the commercially-grown cotton is tetraploid, thus making it much more difficult to target both sets of homeologous alleles. Therefore, in order to understand the efficacy of the CRISPR/Cas9 system to target a gene within the genome of cotton, we made use of a transgenic cotton line previously generated in our laboratory that had a single copy of the green fluorescent protein (GFP) gene integrated into its genome. We demonstrate, for the first time, the use of this powerful new tool in targeted knockout of a gene residing in the cotton genome. By following the loss of GFP fluorescence, we were able to observe the cells that had undergone targeted mutations as a result of CRISPR/Cas9 activity. In addition, we provide examples of the different types of indels obtained by Cas9-mediated cleavage of the GFP gene, guided by three independent sgRNAs. The results provide useful information that will help us target important native genes in the cotton plant in future.

Response of AtNPR1-expressing cotton plants to Fusarium oxysporum f. sp. vasinfectum isolates

In our earlier investigation, we had demonstrated that transgenic cotton plants expressing AtNPR1 showed significant tolerance to Fusarium oxysporum f. sp. vasinfectum, isolate 11 (Fov11) and several other pathogens. The current study was designed to further characterize the nature of the protection provided by AtNPR1 expression and its limitations. Green Fluorescent Protein-expressing Fov11 was generated and used to study the progression of the disease within the plant. The results show that the spread of the pathogen was slower in the AtNPR1-transformants compared to the wild type plants. Transcript analysis in the seedling root and hypocotyl showed that the transgenic lines are capable of launching a stronger defense response when infected with Fov11. We further confirmed that AtNPR1 transformants showed greater degree of tolerance to Fov11. However, little or no protection was observed against a related, but more virulent isolate, Fov43, and a highly virulent isolate, CA9.

Cotton (Gossypium hirsutum L.)

Cotton continues to be a crop of great economic importance in many developing and some developed countries. Cotton plants expressing the Bt gene to deter some of the major pests have been enthusiastically and widely accepted by the farmers in three of the major producing countries, i.e., China, India, and the USA. Considering the constraints related to its production and the wide variety of products derived from the cotton plant, it offers several target traits that can be improved through genetic engineering. Thus, there is a great need to accelerate the application of biotechnological tools for cotton improvement. This requires a simple, yet robust gene delivery/transformant recovery system. Recently, a protocol, involving large-scale, mechanical isolation of embryonic axes from germinating cottonseeds followed by direct transformation of the meristematic cells has been developed by an industrial laboratory. However, complexity of the mechanical device and the patent restrictions are likely to keep this method out of reach of most academic laboratories. In this chapter, we describe the method developed in our laboratory that has undergone further refinements and involves Agrobacterium-mediated transformation of cotton cells, selection of stable transgenic callus lines, and recovery of plants via somatic embryogenesis.

Overexpression of a glutamine synthetase gene affects growth and development in sorghum

Nitrogen is a primary macronutrient in plants, and nitrogen fertilizers play a critical role in crop production and yield. In this study, we investigated the effects of overexpressing a glutamine synthetase (GS) gene on nitrogen metabolism, and plant growth and development in sorghum (Sorghum bicolor L., Moench). GS catalyzes the ATP dependent reaction between ammonia and glutamate to produce glutamine. A 1,071 bp long coding sequence of a sorghum cytosolic GS gene (Gln1) under the control of the maize ubiquitin (Ubq) promoter was introduced into sorghum immature embryos by Agrobacterium-mediated transformation. Progeny of the transformants exhibited higher accumulation of the Gln1 transcripts and up to 2.2-fold higher GS activity compared to the non-transgenic controls. When grown under optimal nitrogen conditions, these Gln1 transgenic lines showed greater tillering and up to 2.1-fold increase in shoot vegetative biomass. Interestingly, even under greenhouse conditions, we observed a seasonal component to both these parameters and the grain yield. Our results, showing that the growth and development of sorghum Gln1 transformants are also affected by N availability and other environmental factors, suggest complexity of the relationship between GS activity and plant growth and development. A better understanding of other control points and the ability to manipulate these will be needed to utilize the transgenic technology to improve nitrogen use efficiency of crop plants.

Enhanced transgene expression in sugarcane by co-expression of virus-encoded RNA silencing suppressors

Post-transcriptional gene silencing is commonly observed in polyploid species and often poses a major limitation to plant improvement via biotechnology. Five plant viral suppressors of RNA silencing were evaluated for their ability to counteract gene silencing and enhance the expression of the Enhanced Yellow Fluorescent Protein (EYFP) or the β-glucuronidase (GUS) reporter gene in sugarcane, a major sugar and biomass producing polyploid. Functionality of these suppressors was first verified in Nicotiana benthamiana and onion epidermal cells, and later tested by transient expression in sugarcane young leaf segments and protoplasts. In young leaf segments co-expressing a suppressor, EYFP reached its maximum expression at 48-96 h post-DNA introduction and maintained its peak expression for a longer time compared with that in the absence of a suppressor. Among the five suppressors, Tomato bushy stunt virus-encoded P19 and Barley stripe mosaic virus-encoded γb were the most efficient. Co-expression with P19 and γb enhanced EYFP expression 4.6-fold and 3.6-fold in young leaf segments, and GUS activity 2.3-fold and 2.4-fold in protoplasts compared with those in the absence of a suppressor, respectively. In transgenic sugarcane, co-expression of GUS and P19 suppressor showed the highest accumulation of GUS levels with an average of 2.7-fold more than when GUS was expressed alone, with no detrimental phenotypic effects. The two established transient expression assays, based on young leaf segments and protoplasts, and confirmed by stable transgene expression, offer a rapid versatile system to verify the efficiency of RNA silencing suppressors that proved to be valuable in enhancing and stabilizing transgene expression in sugarcane.

RNAi-mediated Ultra-low gossypol cottonseed trait: performance of transgenic lines under field conditions

Cottonseed remains a low-value by-product of lint production mainly due to the presence of toxic gossypol that makes it unfit for monogastrics. Ultra-low gossypol cottonseed (ULGCS) lines were developed using RNAi knockdown of δ-cadinene synthase gene(s) in Gossypium hirsutum. The purpose of the current study was to assess the stability and specificity of the ULGCS trait and evaluate the agronomic performance of the transgenic lines. Trials conducted over a period of 3 years show that the ULGCS trait was stable under field conditions and the foliage/floral organs of transgenic lines contained wild-type levels of gossypol and related terpenoids. Although it was a relatively small-scale study, we did not observe any negative effects on either the yield or quality of the fibre and seed in the transgenic lines compared with the nontransgenic parental plants. Compositional analysis was performed on the seeds obtained from plants grown in the field during 2009. As expected, the major difference between the ULGCS and wild-type cottonseeds was in terms of their gossypol levels. With the exception of oil content, the composition of ULGCS was similar to that of nontransgenic cottonseeds. Interestingly, the ULGCS had significantly higher (4%-8%) oil content compared with the seeds from the nontransgenic parent. Field trial results confirmed the stability and specificity of the ULGCS trait suggesting that this RNAi-based product has the potential to be commercially viable. Thus, it may be possible to enhance and expand the nutritional utility of the annual cottonseed output to fulfil the ever-increasing needs of humanity.

Enhanced resistance against Thielaviopsis basicola in transgenic cotton plants expressing Arabidopsis NPR1 gene

Black root rot, caused by Thielaviopsis basicola, is an important disease in several crops including cotton. We studied the response of Arabidopsis NPR1 (AtNPR1)-expressing cotton lines, previously shown to be highly resistant to a diverse set of pathogens, to a challenge from T. basicola. In four different experiments, we found significant degree of tolerance in the transgenic lines to black root rot. Although transformants showed the typical root discoloration symptoms similar to the wild-type control plants following infection, their roots tended to recover faster and resumed normal growth. Better performance of transgenic plants is reflected by the fact that they have significantly higher shoot and root mass, longer shoot length, and greater number of boll-set. Transcriptional analysis of the defense response showed that the roots of AtNPR1-overexpressing transgenic plants exhibited stronger and faster induction of most of these defense-related genes, particularly PR1, thaumatin, glucanase, LOX1, and chitinase. The results obtained in this investigation provide further support for a broad-spectrum nature of the resistance conferred by overexpression of AtNPR1 gene in cotton.

Ultra-low gossypol cottonseed: generational stability of the seed-specific, RNAi-mediated phenotype and resumption of terpenoid profile following seed germination

Cottonseed, containing 22.5% protein, remains an under-utilized and under-valued resource because of the presence of toxic gossypol. RNAi-knockdown of δ-cadinene synthase gene(s) was used to engineer plants that produced ultra-low gossypol cottonseed (ULGCS). In the original study, we observed that RNAi plants, a month or older, maintain normal complement of gossypol and related terpenoids in the roots, foliage, floral organs, and young bolls. However, the terpenoid levels and profile of the RNAi lines during the early stages of germination, under normal conditions and in response to pathogen exposure, had not been examined. Results obtained in this study show that during the early stages of seed germination/seedling growth, in both non-transgenic and RNAi lines, the tissues derived directly from bulk of the seed kernel (cotyledon and hypocotyl) synthesize little, if any new terpenoids. However, the growing root tissue and the emerging true leaves of RNAi seedlings showed normal, wild-type terpenoid levels. Biochemical and molecular analyses showed that pathogen-challenged parts of RNAi seedlings are capable of launching a terpenoid-based defence response. Nine different RNAi lines were monitored for five generations. The results show that, unlike the unstable nature of antisense-mediated low seed-gossypol phenotype, the RNAi-mediated ULGCS trait exhibited multi-generational stability.

A novel, conditional, lesion mimic phenotype in cotton cotyledons due to the expression of an endochitinase gene from Trichoderma virens

We have observed a novel, lesion mimic phenotype (LMP) in the cotyledons of cotton seedlings expressing an endochitinase gene from Trichoderma virens. This phenotype, however, is conditional and is elicited only when the transgenic seedlings are germinating on a medium that is devoid of mineral nutrients. The LMP manifests itself around the 5th day in the form of scattered, dry necrotic lesions on the cotyledons. The severity of the LMP is correlated with the level of transgene activity. Production of reactive oxygen species and activities of certain defense related enzymes and genes were substantially higher in the cotyledons of seedlings that were growing under mineral nutrient stress. Molecular and biochemical analyses indicated significantly higher-level activities of certain defense-related genes/enzymes at the onset of the phenotype. Treatment with methyl jasmonate can induce LMP in the cotyledons of wild-type (WT) seedlings similar to that observed in the endochitinase-expressing seedlings grown on nutrient-free medium. On the other hand, salicylic acid (SA), its functional analog, benzo(1,2,3) thiadiazole-7-carbothioic acid (BTH), and ibuprofen can rescue the LMP induced by the seedling-growth on nutrient-deficient medium. Nutrient deficiency-induced activation of a defense response appears to be the contributing factor in the development of LMP in endochitinase-expressing cotton seedlings.

Citrus limonin and its glucoside inhibit colon adenocarcinoma cell proliferation through apoptosis

The current study was an attempt to elucidate the mechanism of human colon cancer cell proliferation inhibition by limonin and limonin glucoside (LG) isolated from seeds of Citrus reticulata. The structures of purified compounds were confirmed by NMR and quantified using HPLC. These compounds of more than 95% purity were subjected to proliferation inhibition assay using human colon adenocarcinoma (SW480) cells. The IC50 value of 54.74 and 37.39 μM was observed for limonin and LG, respectively at 72 h. Following confirmation of proliferation inhibition, pattern of DNA fragmentation and activation of caspase-3 of the cells treated with limonoids suggest involvement of apoptosis. Furthermore, reduction in the transcription ratio of bcl2/bax and induction of cytochrome c release from mitochondria to cytosol with treatment of limonoids confirm the activation of intrinsic apoptosis pathway. The activity of Bax and Bcl2 was confirmed through analysis of mitochondrial membrane potential and intracellular calcium in the cells treated with limonin and LG; the net content of caspase-8 was not affected by limonoids. Results of the current study provide compelling evidence on the induction of mitochondria mediated intrinsic apoptosis by both limonin and LG in cultured SW480 cells for the first time.

Sugarcane DIRIGENT and O-methyltransferase promoters confer stem-regulated gene expression in diverse monocots

Transcription profiling analysis identified Saccharum hybrid DIRIGENT (SHDIR16) and Omicron-Methyltransferase (SHOMT), putative defense and fiber biosynthesis-related genes that are highly expressed in the stem of sugarcane, a major sucrose accumulator and biomass producer. Promoters (Pro) of these genes were isolated and fused to the beta-glucuronidase (GUS) reporter gene. Transient and stable transgene expression analyses showed that both Pro( DIR16 ):GUS and Pro( OMT ):GUS retain the expression characteristics of their respective endogenous genes in sugarcane and function in orthologous monocot species, including rice, maize and sorghum. Furthermore, both promoters conferred stem-regulated expression, which was further enhanced in the stem and induced in the leaf and root by salicylic acid, jasmonic acid and methyl jasmonate, key regulators of biotic and abiotic stresses. Pro( DIR16 ) and Pro( OMT ) will enable functional gene analysis in monocots, and will facilitate engineering monocots for improved carbon metabolism, enhanced stress tolerance and bioenergy production.

A kinetic analysis on non-isothermal glass-crystal transformation in Ge(1-x)Sn(x)Se(2.5) (0 ≤ x ≤ 0.5) glasses

Differential scanning calorimetry (DSC) has been employed at five different heating rates to investigate the glass-crystal transformation in Ge(1-x)Sn(x)Se(2.5) (0≤x≤0.5) glasses under non-isothermal conditions. From the dependence of glass transition temperature on the heating rate 'α' , the activation energy of glass transition, E(t), has been calculated on the basis of the Kissinger model. Results indicate that T(g) and E(t) attain their minimum values at 0.3 at. wt% of Sn. The crystallization process has been investigated using Kissinger, Matusita, Augis and Bennett, and Gao and Wang models. Various kinetic parameters such as activation energy of crystallization, E(c), Avrami exponent (n), dimensionality of growth (m), frequency factor (K(o)) and crystallization rate factor (K) have been calculated for a better understanding of the growth mechanism. The obtained kinetic parameters indicate that stability of glassy samples decreases upto 0.3 at. wt% of Sn and increases on further addition of Sn.

Defense-related gene expression and enzyme activities in transgenic cotton plants expressing an endochitinase gene from Trichoderma virens in response to interaction with Rhizoctonia solani

There are many reports on obtaining disease-resistance trait in plants by overexpressing genes from diverse organisms that encode chitinolytic enzymes. Current study represents an attempt to dissect the mechanism underlying the resistance to Rhizoctonia solani in cotton plants expressing an endochitinase gene from Trichoderma virens. Several assays were developed that provided a powerful demonstration of the disease protection obtained in the transgenic cotton plants. Transgene-dependent endochitinase activity was confirmed in various tissues and in the medium surrounding the roots of transformants. Biochemical and molecular analyses conducted on the transgenic plants showed rapid/greater induction of ROS, expression of several defense-related genes, and activation of some PR enzymes and the terpenoid pathway. Interestingly, even in the absence of a challenge from the pathogen, the basal activities of some of the defense-related genes and enzymes were higher in the endochitinase-expressing cotton plants. This elevated defensive state of the transformants may act synergistically with the potent, transgene-encoded endochitinase activity to confer a strong resistance to R. solani infection.

Expression of anti-K99 scFv in transgenic rice tissues and its functional characterization

As a first step towards manufacturing functional anti-K99 single chain variable antibody fragment (scFv) in a plant system to prevent colibacillosis in neonatal calves, we investigated the feasibility of producing these antibodies in rice plants. Two scFv constructs, with or without the endoplasmic reticulum (ER) targeting KDEL sequence, were introduced into rice for either ER-retention of the recombinant antibody or its secretion. In agreement with several other published reports, extremely low-levels of scFv were produced in rice plants transformed with the construct lacking the ER-targeting sequence. Constructs containing the KDEL sequence resulted in significantly higher levels of the antibody in rice leaves. Although scFv transcripts were found in all three rice tissues analyzed, scFv protein was detected only in the leaf and embryo tissues and not in the endosperm portion of the seed. Functionality of the rice-produced scFv was tested in two in vitro assays, i.e., inhibition of K99-induced horse red blood cell agglutination and inhibition of the attachment of enterotoxigenic Escherichia coli (ETEC) to calf enterocytes. Rice-scFv was found to be functionally equivalent to anti-K99 monoclonal antibody (mAb) in both the assays. The results obtained in this investigation provide valuable information and in combination with other studies of this kind, will be helpful in devising strategies to improve production of useful recombinant proteins in the seeds.

Rheumatic mitral valve surgery in the fifth decade: our experience

AIM

Rheumatic mitral patients reach their fifth decade of life more often now than in the past. The purpose of this study is to provide insight into improving morbidity and mortality in these patients.

METHODS

This retrospective study included 105 patients aged 50 years or more. Seventy-five underwent mechanical valve replacement and 30 received a bioprosthetic valve. Data were collected from medical records and outpatient department (OPD) registers. Follow-up included transthoracic 2D echocardiography, supported by clinical parameters, and X-ray findings.

RESULTS

Mean age was 58.52+/-2.4 years. Follow-up period ranged from one to eleven years (mean 6.8+/-0.9 years). Immediate perioperative mortality included five patients (4.76%) and long term mortality included three patients (3%). 35 patients previously underwent closed and open commissurotomy and balloon valvotomy. Multivariate analysis showed age, repeat surgery, atrial fibrillation, tricuspid valve disease, and preoperative functional status to be incremental risk factors. Freedom from repeat operation at 3 and 6 years was 90% and 85% in group I (<60 years), respectively. Actuarial survival at 4 and 6 years of follow up was 94.24% and 88.52%, respectively.

CONCLUSION

With improving life expectancy and early interventions, the number of < or = 50-year old rheumatic valvular disease patients is increasing. The present study showed a marked improvement for this subset of patients, although age still remains the main risk factor along with atrial fibrillation, repeat surgery, stroke and tricuspid valve disease.

Regulation of telomerase in Arabidopsis by BT2, an apparent target of TELOMERASE ACTIVATOR1

Telomerase, an enzyme essential for the synthesis and maintenance of telomeric DNA and the long-term stability of the genome, is developmentally regulated in plants. Telomerase activity is abundant in reproductive organs but low or undetectable in vegetative organs. Treatment with exogenous auxin, however, overrides this developmental control and induces telomerase in mature leaves. The Arabidopsis thaliana transcription factor TELOMERASE ACTIVATOR1 (TAC1) potentiates some responses to auxin, including the induction of telomerase activity in leaves. Here, we report that BT2, a protein with BTB, TAZ, and calmodulin binding domains, is an essential component of the TAC1-mediated telomerase activation pathway. Steady state concentration of BT2 mRNA increases in response to TAC1 expression, and TAC1 specifically binds the BT2 promoter both in vitro and in yeast one-hybrid assays. Constitutive expression of BT2 induces telomerase activity in leaves, whereas a null mutation of BT2 blocks TAC1-mediated telomerase induction, indicating that BT2 acts downstream of TAC1 to regulate telomerase activity in mature vegetative organs.

Engineering cottonseed for use in human nutrition by tissue-specific reduction of toxic gossypol

Global cottonseed production can potentially provide the protein requirements for half a billion people per year; however, it is woefully underutilized because of the presence of toxic gossypol within seed glands. Therefore, elimination of gossypol from cottonseed has been a long-standing goal of geneticists. Attempts were made to meet this objective by developing so-called "glandless cotton" in the 1950s by conventional breeding techniques; however, the glandless varieties were commercially unviable because of the increased susceptibility of the plant to insect pests due to the systemic absence of glands that contain gossypol and other protective terpenoids. Thus, the promise of cottonseed in contributing to the food requirements of the burgeoning world population remained unfulfilled. We have successfully used RNAi to disrupt gossypol biosynthesis in cottonseed tissue by interfering with the expression of the delta-cadinene synthase gene during seed development. We demonstrate that it is possible to significantly reduce cottonseed-gossypol levels in a stable and heritable manner. Results from enzyme activity and molecular analyses on developing transgenic embryos were consistent with the observed phenotype in the mature seeds. Most relevant, the levels of gossypol and related terpenoids in the foliage and floral parts were not diminished, and thus their potential function in plant defense against insects and diseases remained untouched. These results illustrate that a targeted genetic modification, applied to an underutilized agricultural byproduct, provides a mechanism to open up a new source of nutrition for hundreds of millions of people.

Cotton (Gossypium hirsutum L.)

Considering the economic importance of cotton in many developing and developed countries, there is an urgent need to accelerate the application of biotechnological tools to address the problems associated with the production of this crop and to improve the quality of fiber and seed. This requires a simple yet robust gene delivery/transformant recovery system. A protocol for the production of transgenic cotton plants was refined in our laboratory. It involves Agrobacterium-mediated transformation of cotton cells, selection of stable transgenic callus lines, and recovery of plants via somatic embryogenesis. A detailed description of the protocol is provided in this chapter.

A comprehensive study of the use of a homologous promoter in antisense cotton lines exhibiting a high seed oleic acid phenotype

As opposed to first-generation biotechnology products, such as pest-resistant crops and herbicide-resistant crops, second-generation products often utilize plant-derived, homologous or heterologous genes and/or promoters. In this study, we evaluated the ability of a promoter from a gene encoding a major storage protein in cottonseed to drive an antisense sequence of the cotton FAD2 gene to down-regulate the activity of Delta-12 desaturase enzyme in cottonseeds. The oleic acid level in the transgenic cottonseeds approximately doubled from the wild-type level of 15%, with a concomitant decrease in the level of linoleic acid. A more extensive study of one line revealed a higher degree of seed-to-seed variability in the transgenic phenotype. A thorough investigation was conducted to determine the impact of the use of a homologous promoter to drive a transgene on the activity of the endogenous promoter. The results showed that the use of the homologous alpha-globulin B promoter for transgenic purposes did not adversely affect the expression of alpha-globulin B storage protein in cottonseed. The results obtained in this investigation on the use of a homologous promoter and antisense technology will be useful in the design of strategies to alter biosynthetic pathways for nutritional quality improvements and for the production of heterologous proteins of commercial value in seeds.

Enterotoxigenic K99+ Escherichia coli attachment to host cell receptors inhibited by recombinant pili protein

Most enterotoxigenic Escherichia coli (ETEC) isolated from neonatal cattle with diarrhea (enteric colibacillosis) exhibit the colonization factor antigen, K99. The K99 pili are necessary for the bacteria to bind to a receptor, N-glycolylneuraminic acid-GM3 on the host cells in the small intestine where the bacteria multiply and secrete toxins that cause the diarrhea. When the attachment of the ETEC to host cell is inhibited, the bacteria do not accumulate sufficiently in the gut to cause disease. Since purified K99 pili block K99+ ETEC from binding to host epithelia, three recombinant K99 proteins of different sizes were developed and produced to demonstrate inhibition with in vitro competitive binding assays. The full-length recombinant protein, rK99-476 inhibited the binding of ETEC with an activity similar to that of the native purified K99, whereas the truncated recombinant K99 protein had no inhibitory activity. Thus this binding activity of rK99-476, which is specific and effective in blocking the receptors on the host cells, may be able to competitively inhibit K99+ ETEC infections in cattle.

Enhanced fungal resistance in transgenic cotton expressing an endochitinase gene from Trichoderma virens

Mycoparasitic fungi are proving to be rich sources of antifungal genes that can be utilized to genetically engineer important crops for resistance against fungal pathogens. We have transformed cotton and tobacco plants with a cDNA clone encoding a 42 kDa endochitinase from the mycoparasitic fungus, Trichoderma virens. Plants from 82 independently transformed callus lines of cotton were regenerated and analysed for transgene expression. Several primary transformants were identified with endochitinase activities that were significantly higher than the control values. Transgene integration and expression was confirmed by Southern and Northern blot analyses, respectively. The transgenic endochitinase activities were examined in the leaves of transgenic tobacco as well as in the leaves, roots, hypocotyls and seeds of transgenic cotton. Transgenic plants with elevated endochitinase activities also showed the expected 42 kDa endochitinase band in fluorescence, gel-based assays performed with the leaf extracts in both species. Homozygous T2 plants of the high endochitinase-expressing cotton lines were tested for disease resistance against a soil-borne pathogen, Rhizoctonia solani and a foliar pathogen, Alternaria alternata. Transgenic cotton plants showed significant resistance to both pathogens.

Developmental and tissue-specific expression of CaMV 35S promoter in cotton as revealed by GFP

The CaMV 35S promoter is the most commonly used promoter for driving transgene expression in plants. Though it is presumed to be a constitutive promoter, some reports suggest that it is not expressed in all cell types. In addition, the information available on its expression profile in all possible cell and tissue types and during early stages of development is incomplete. We present here a detailed expression profile of this promoter investigated using the green fluorescent protein (GFP) gene as a reporter system in cotton during embryo development, and in all the vegetative and floral cell and tissue types. GFP expression was not detected during the early stages of embryogenesis. The first perceptible GFP expression was observed in a small area at the junction of hypocotyl and cotyledons in embryos at around 13 days after anthesis. The GFP fluorescence progressively became stronger and expanded throughout the cotyledon and hypocotyl as embryo development advanced. After germination, varying levels of promoter activity were observed in all cell and tissue types in the hypocotyl, cotyledon, stem, leaf, petiole, and root. The promoter was also expressed in all floral parts. Although cotton pollen exhibited a low level of greenish autofluorescence, it was possible to discern GFP-dependent fluorescence in some of the pollen from all the T0 plants examined. Developing cotton fibers also exhibited GFP fluorescence suggesting that the 35S promoter was active in these specialized epidermal cells. Thus, we show that the expression of the 35S promoter was developmentally regulated during embryogenesis and that beyond a certain stage during embryogenesis, the promoter was expressed in most cell and tissue types in cotton albeit at different levels.

Cotton alpha-globulin promoter: isolation and functional characterization in transgenic cotton, Arabidopsis, and tobacco

Globulins are the most abundant seed storage proteins in cotton and, therefore, their regulatory sequences could potentially provide a good source of seed-specific promoters. We isolated the putative promoter region of cotton alpha-globulin B gene by gene walking using the primers designed from a cotton staged embryo cDNA clone. PCR amplified fragment of 1108 bp upstream sequences was fused to gusA gene in the binary vector pBI101.3 to create the test construct. This was used to study the expression pattern of the putative promoter region in transgenic cotton, Arabidopsis, and tobacco. Histochemical GUS analysis revealed that the promoter began to express during the torpedo stage of seed development in tobacco and Arabidopsis, and during cotyledon expansion stage in cotton. The activity quickly increased until embryo maturation in all three species. Fluorometric GUS analysis showed that the promoter expression started at 12 and 15 dpa in tobacco and cotton, respectively, and increased through seed maturation. The strength of the promoter expression, as reflected by average GUS activity in the seeds from primary transgenic plants, was vastly different amongst the three species tested. In Arabidopsis, the activity was 16.7% and in tobacco it was less than 1% of the levels detected in cotton seeds. In germinating seedlings of tobacco and Arabidopsis, GUS activity diminished until it was completely absent 10 days post imbibition. In addition, absence of detectable level of GUS expression in stem, leaf, root, pollen, and floral bud of transgenic cotton confirmed that the promoter is highly seed-specific. Analysis of GUS activity at individual seed level in cotton showed a gene dose effect reflecting their homozygous or hemizygous status. Our results show that this promoter is highly tissue-specific and it can be used to control transgene expression in dicot seeds.

Expression of snowdrop lectin (GNA) in transgenic rice plants confers resistance to rice brown planthopper

Snowdrop lectin (Galanthus nivalis agglutinin; GNA) has been shown previously to be toxic towards rice brown planthopper (Nilaparvata lugens; BPH) when administered in artificial diet. BPH feeds by phloem abstraction, and causes 'hopper burn', as well as being an important virus vector. To evaluate the potential of the gna gene to confer resistance towards BPH, transgenic rice (Oryza sativa L.) plants were produced, containing the gna gene in constructs where its expression was driven by a phloem-specific promoter (from the rice sucrose synthase RSs1 gene) and by a constitutive promoter (from the maize ubiquitin ubi1 gene). PCR and Southern analyses on DNA from these plants confirmed their transgenic status, and that the transgenes were transmitted to progeny after self-fertilization. Western blot analyses revealed expression of GNA at levels of up to 2.0% of total protein in some of the transgenic plants. GNA expression driven by the RSs1 promoter was tissue-specific, as shown by immunohistochemical localization of the protein in the non-lignified vascular tissue of transgenic plants. Insect bioassays and feeding studies showed that GNA expressed in the transgenic rice plants decreased survival and overall fecundity (production of offspring) of the insects, retarded insect development, and had a deterrent effect on BPH feeding. gna is the first transgene to exhibit insecticidal activity towards sap-sucking insects in an important cereal crop plant.

Use of bar as a selectable marker gene and for the production of herbicide-resistant rice plants from protoplasts

We have used the bar gene in combination with the herbicide Basta to select transformed rice (Oryza sativa L. cv. Radon) protoplasts for the production of herbicide-resistant rice plants. Protoplasts, obtained from regenerable suspension cultures established from immature embryo callus, were transformed using PEG-mediated DNA uptake. Transformed calli could be selected 2-4 weeks after placing the protoplast-derived calli on medium containing the selective agent, phosphinothricin (PPT), the active component of Basta. Calli resistant to PPT were capable of regenerating plants. Phosphinothricin acetyltransferase (PAT) assays confirmed the expression of the bar gene in plants obtained from PPT-resistant calli. The only exceptions were two plants obtained from the same callus that had multiple copies of the bar gene integrated into their genomes. The transgenic status of the plants was verified by Southern blot analysis. In our system, where the transformation was done via the protoplast method, there were very few escapes. The efficiency of co-transformation with a reporter gene gusA, was 30%. The T0 plants of Radon were self-fertile. Both the bar and gusA genes were transmitted to progeny as confirmed by Southern analysis. Both genes were expressed in T1 and T2 progenies. Enzyme analyses on T1 progeny plants also showed a gene dose response reflecting their homozygous and heterozygous status. The leaves of T0 plants and that of the progeny having the bar gene were resistant to application of Basta. Thus, the bar gene has proven to be a useful selectable and screenable marker for the transformation of rice plants and for the production of herbicide-resistant plants.

A cytoplasmic gradient of Ca2+ is correlated with the growth of lily pollen tubes

We have measured the distribution of cytoplasmic calcium in lily pollen tubes by microinjecting them with indo-1 and performing fluorescence ratio image analysis on them. All of the 16 tubes that were growing at the time of the calcium measurements showed a gradient of [Ca2+]i in the tip region, with Ca2+ being 1.25 to 3.32 times higher at the distal end in 15 cases and more than 5 times higher in one case. The extent of the gradient ranged from 22 to 65 microns. Most of the 15 nongrowing tubes either had no gradient or had lower Ca2+ in the tip region. While we have confirmed a previous report that lily pollen tubes can be loaded with the membrane-permeable acetoxymethyl ester forms of calcium indicators, the dyes loaded in this way are visibly partitioned into organelles and this method of loading is, therefore, not useful for the measurement of [Ca2+]i. Iontophoresis of the dye free acids into tubes produces a more uniform and diffuse fluorescence which does not appear to partition into organelles. Indo-1 remains in the pollen tubes longer than fura-2. The correlation between growth and the [Ca2+]i gradient in the apical portion of the pollen tube is discussed in relation to previous reports that have suggested that such a gradient should exist during polarized growth.

A Two-Dimensional Vibrating Probe Study of Currents around Lateral Roots of Raphanus sativus Developing in Culture

A computer-assisted, two-dimensional vibrating probe was used to study the ionic currents around developing lateral roots of Raphanus sativus in vitro. This system allowed us to superimpose current vectors on the video image of the roots. In a young lateral root, current entered the cap, meristematic, and elongation zones and exited the primary root surface close to the base of the lateral root. As the lateral root grew, current began to exit from its basal (cell maturation zone) end. The densities of currents entering the apical portion of the faster-growing lateral roots in a medium lacking indole 3-acetic acid were about twice as large as those entering the apical region of the slower-growing lateral roots in indole 3-acetic acid-supplemented medium.

The responses of pollen to applied electrical fields

The growing pollen tubes of tomato and tobacco were exposed to electrical fields and the effect on the direction of growth was measured. They responded by turning toward the positive electrode (anode) and gave a detectable response in fields as small as 0.1 mV/tube diameter. The sites of germination of tobacco pollen grains were also affected by applied fields; the pollen tubes tended to emerge from the anodal side. This effect was detectable at a field of 0.4 mV/grain diameter.

A refined technique to apply electrical currents to callus cultures

A simple, inexpensive technique is described which can be used to pass small electrical currents of a few microamperes through callus cultures under sterile conditions without contaminating the tissue or the medium with electrode products. Application of 1 or 2 microamperes currents of either polarity stimulated growth as well as shoot regeneration in tobacco (Nicotiana tabacum var. virginica) callus cultures, indicating that these effects are due to the electrical fields set up by the exogenous currents, rather than by electrode products.

Ionic basis of currents in somatic embryos of Daucus carota

A vibrating probe was used to measure extracellular electrical currents around developing somatic embryos in two lines (RCC27, RCC48) of cultured cells of Daucus carota L. at the heart and torpedo stages. At pH 5.5, an inward current of 1.2±0.1 μA·cm(-2) (n=23) was detected at the cotyledon, and an outward current of 1.0±0.1 μA·cm(-2) (n=22) was found at the radicle in torpedostage embryos from the RCC27 line. At a pH of 5.75 the currents increased by 0.2-0.3 μA·cm(-2) (n=60-62). In a few cases an additional small inward current was detected at the tip of the radicle in toepedo-stage embryos from RCC27 line. Such an inward current at the radicle seemed to appear earlier, some time after the heart stage, in embryos from the RCC48 line.Both extracellular pH measurements (using microelectrodes filled with ion-sensitive resin) and ion-substitution studies were carried out in order to ascertain the ionic composition of the currents in torpedo-stage embryos from the RCC27 line. Regions adjacent to the cotyledon and radicle, at the points of current entry and exit, were found to be more acidic by 0.02±0.01 (n=14) and 0.07±0.01 (n=12) pH units, respectively, than the bulk medium. Removal of K(+) from the medium reversibly reduced the currents to about 25% of their original value at both cotyledon and radicle. Deletion of Cl(-) decreased the currents slightly. Removal of Ca(2+) resulted in a rapid doubling of currents. Addition of either N,N'-dicyclohexylcarbodiimide or tetraethyl ammonium chloride substantially reduced overall currents, and their removal resulted in partial recovery of the currents. It is suggested that the inward current at the cotyledon is comprised largely of K(+) influx and the outward current at the radicle is mainly the result of active H(+) efflux.