Tertiary prevention and treatment of rheumatic heart disease: a National Heart, Lung, and Blood Institute working group summary

Although entirely preventable, rheumatic heart disease (RHD), a disease of poverty and social disadvantage resulting in high morbidity and mortality, remains an ever-present burden in low-income and middle-income countries (LMICs) and rural, remote, marginalised and disenfranchised populations within high-income countries. In late 2021, the National Heart, Lung, and Blood Institute convened a workshop to explore the current state of science, to identify basic science and clinical research priorities to support RHD eradication efforts worldwide. This was done through the inclusion of multidisciplinary global experts, including cardiovascular and non-cardiovascular specialists as well as health policy and health economics experts, many of whom also represented or closely worked with patient-family organisations and local governments. This report summarises findings from one of the four working groups, the Tertiary Prevention Working Group, that was charged with assessing the management of late complications of RHD, including surgical interventions for patients with RHD. Due to the high prevalence of RHD in LMICs, particular emphasis was made on gaining a better understanding of needs in the field from the perspectives of the patient, community, provider, health system and policy-maker. We outline priorities to support the development, and implementation of accessible, affordable and sustainable interventions in low-resource settings to manage RHD and related complications. These priorities and other interventions need to be adapted to and driven by local contexts and integrated into health systems to best meet the needs of local communities.

Recommendations for developing effective and safe paediatric and congenital heart disease services in low-income and middle-income countries: a public health framework

The global burden of paediatric and congenital heart disease (PCHD) is substantial. We propose a novel public health framework with recommendations for developing effective and safe PCHD services in low-income and middle-income countries (LMICs). This framework was created by the Global Initiative for Children's Surgery Cardiac Surgery working group in collaboration with a group of international rexperts in providing paediatric and congenital cardiac care to patients with CHD and rheumatic heart disease (RHD) in LMICs. Effective and safe PCHD care is inaccessible to many, and there is no consensus on the best approaches to provide meaningful access in resource-limited settings, where it is often needed the most. Considering the high inequity in access to care for CHD and RHD, we aimed to create an actionable framework for health practitioners, policy makers and patients that supports treatment and prevention. It was formulated based on rigorous evaluation of available guidelines and standards of care and builds on a consensus process about the competencies needed at each step of the care continuum. We recommend a tier-based framework for PCHD care integrated within existing health systems. Each level of care is expected to meet minimum benchmarks and ensure high-quality and family centred care. We propose that cardiac surgery capabilities should only be developed at the more advanced levels on hospitals that have an established foundation of cardiology and cardiac surgery services, including screening, diagnostics, inpatient and outpatient care, postoperative care and cardiac catheterisation. This approach requires a quality control system and close collaboration between the different levels of care to facilitate the journey and care of every child with heart disease. This effort was designed to guide readers and leaders in taking action, strengthening capacity, evaluating impact, advancing policy and engaging in partnerships to guide facilities providing PCHD care in LMICs.

Phytoextraction efficiency of Pteris vittata grown on a naturally As-rich soil and characterization of As-resistant rhizosphere bacteria

This study evaluated the phytoextraction capacity of the fern Pteris vittata grown on a natural arsenic-rich soil of volcanic-origin from the Viterbo area in central Italy. This calcareous soil is characterized by an average arsenic concentration of 750 mg kg⁻¹, of which 28% is bioavailable. By means of micro-energy dispersive X-ray fluorescence spectrometry (μ-XRF) we detected As in P. vittata fronds after just 10 days of growth, while a high As concentrations in fronds (5,000 mg kg⁻¹), determined by Inductively coupled plasma-optical emission spectrometry (ICP-OES), was reached after 5.5 months. Sixteen arsenate-tolerant bacterial strains were isolated from the P. vittata rhizosphere, a majority of which belong to the Bacillus genus, and of this majority only two have been previously associated with As. Six bacterial isolates were highly As-resistant (> 100 mM) two of which, homologous to Paenarthrobacter ureafaciens and Beijerinckia fluminensis, produced a high amount of IAA and siderophores and have never been isolated from P. vittata roots. Furthermore, five isolates contained the arsenate reductase gene (arsC). We conclude that P. vittata can efficiently phytoextract As when grown on this natural As-rich soil and a consortium of bacteria, largely different from that usually found in As-polluted soils, has been found in P. vittata rhizosphere.

Pediatric Cardiac Service Development Programs for Low- and Middle-Income Countries in Need of Improving or Initiating Local Services

Pediatric cardiac services are deficient in most of the world. Various estimates are that between 80 and 90% of the world's children do not receive adequate cardiac care for their congenital or acquired heart disease. We began a modest effort in 1992 to assist in the development of pediatric cardiac services in low- and middle-Income countries (LMIC). Since then, we have provided services in 32 countries based on 3 distinctive development strategies, in order to meet the local needs for pediatric cardiac services. Our goal has always been to provide education, training and sufficient experience so that eventually we leave a site with a fully functional, independently operating pediatric cardiac service that is sustainable over time. The margin between success and failure is dependent upon a number of factors and we hope that this chapter will provide others with the tools for success.

Potential Deleterious Interactions between Certain Chemical Compounds and a Thermoplastic Polyurethane Heat Exchanger Membrane Oxygenator

Extracorporeal membrane oxygenation (ECMO) has become a powerful tool in the race to reverse failure to rescue events. Rapid implementation set the stage for the advent of the 30-day wet-priming storage as a standard practice. A recent alert regarding methylene blue (MB) unidirectional leach from patient's circulation through the oxygenator thermoplastic polyurethane (TPU) heat-exchanger membrane into the heater-cooler unit (HCU) water bath led us to believe that despite reassurances, the reverse process might be possible. To that effect, we performed a pilot in vitro experiment. We tested three adult ECMO sets (Adult Quadrox iD Oxygenator, Getinge, Doral, FL) probing for the transfer of MB between the water bath of a Sarns Dual Heater Cooler (Terumo Corporation, Ann Arbor, MI) and the circuit stored wet-primed for 30 days. In each test, 1,500 mg of reconstituted MB (HiMedia, Mumbai, India) were added to the 7.5 L of water in the HCU, circulated for 6 hours on which the water lines were disconnected and the setup was stored for 30 days. The primed circuit was tested for MB transfer at days 0, 13, and 30 by means of optical density (OD) at 665 nm and 26.5°C. Transference of MB from the HCU water bath into the ECMO circuit could be detected as early as day 13 after setup, achieving significant values by day 30 (median OD .019 (.014-.021). Expected OD if no diffusion present: 0. The complete separation of water interfaces between the patient's circuit and the HCU water bath may prove to be more dogma than fact when certain chemical substances are used in conjunction with TPU membrane oxygenators. Whether the transfer of substances is due to chemical processes or molecular weight needs further evaluation. Meanwhile, the use of chemicals for the cleaning of the HCU should be mindful of potential noxious effects.

Cost-effectiveness of Humanitarian Pediatric Cardiac Surgery Programs in Low- and Middle-Income Countries

IMPORTANCE

Endorsement of global humanitarian interventions is based on either proven cost-effectiveness or perceived public health benefits. The cost-effectiveness and long-term benefits of global humanitarian pediatric cardiac surgery are unknown, and funding for this intervention is insufficient.

OBJECTIVES

To determine the cost-effectiveness of the intervention (multiple 2-week-long humanitarian pediatric cardiac surgery program assistance trips to various low- and middle-income countries [LMICs]) and to produce a measure of the long-lasting effects of global humanitarian programs.

DESIGN, SETTING, AND PARTICIPANTS

International, multicenter cost-effectiveness analysis of a cohort of children (aged <16 years) undergoing surgical treatment of congenital heart disease during 2015 in LMICs, including China, Macedonia, Honduras, Iran, Iraq, Libya, Nigeria, Pakistan, Russia, and Ukraine. The study also assessed estimated improvement in the United Nations Human Development Indicators (life expectancy, years of schooling, and gross national income) for each individual survivor, as a proxy for long-term benefits of the intervention.

MAIN OUTCOMES AND MEASURES

The primary outcome was cost-effectiveness of the intervention. The secondary outcomes were potential gains in life expectancy, years of schooling, and gross national income per capita for each survivor.

RESULTS

During 2015, 446 patients (192 [43%] female; mean [SD] age, 3.7 [5.4] years) were served in 10 LMICs at an overall cost of $3 210 873. Of them, 424 were children. The cost-effectiveness of the intervention was $171 per disability-adjusted life-year averted. Each survivor in the cohort (390 of 424) potentially gained 39.9 disability-adjusted life-years averted, 3.5 years of schooling, and $159 533 in gross national income per capita during his or her extended lifetime at purchasing power parity and 3% discounting.

CONCLUSIONS AND RELEVANCE

Humanitarian pediatric cardiac surgery in LMICs is highly cost-effective. It also leaves behind a lasting humanitarian footprint by potentially improving individual development indices.

Establishing Sustainable Cardiothoracic Surgery Programs in Underserved Countries

Congenital heart disease is the most common birth defect worldwide, and accounts for a high proportion of the world's infant mortality. About 9 of every 10 babies born each year are born in areas without adequate access to heart surgery; overcoming this problem will necessitate addressing the worldwide shortage of an estimated 3,700 pediatric cardiac surgeons. Establishing sustainable heart surgery programs requires more than an investment of money: political, social, and cultural issues unique to each environment need to be addressed. Organizations desiring to help develop cardiac surgical centers need to focus on communication and bidirectional education, and to make a long-term commitment to each site. By identifying and addressing obstacles, success rates are high.

Dissecting multidisciplinary cardiac surgery rounds

BACKGROUND

Multidisciplinary rounds in the critical care environment have demonstrated increased communication, a reduction in medical errors, a shorter hospital stay, and consequently, economic savings. We attempt to assess the cost of this intervention, and to review the time utilization of professionals participating in the process.

METHODS

We analyzed video-recorded weekly multidisciplinary teaching rounds on cardiac patients in a pediatric intensive care unit (n = 22). Rounding time was categorized as presentation or discussion and was measured in minutes. The cost of a round was calculated by multiplying the hourly salary of all healthcare professionals present by the time spent rounding and measured in US dollars.

RESULTS

Median rounding time per patient was 15 minutes (range, 5 to 29). Patient presentation took between 2 and 8 minutes (median 4), or 26% of the rounding time. Time needed for discussion, including teaching and planning, varied between 2 and 25 minutes (median 10.5). Median number of participants was 13.5 (range, 11 and 16). Mean cost in salaries per patient rounded was $140.87 (95% confidence interval: $106.80 to $174.90).

CONCLUSIONS

Multidisciplinary rounds are a low-cost medical intervention with proven benefits. Available tools and rounding cultural changes should be adopted to shorten data retrieval and presentation time to the benefit of discussion and teaching. Current billing requirements for rounding multidisciplinary teams do not reflect the realities of their time use.

A computing platform to support communication and sense-making in intensive care

We developed a conceptual design of a mobile computing platform to support multi-disciplinary rounds in intensive care units.

Diagnostic value of PRND gene expression profiles in astrocytomas: relationship to tumor grades of malignancy

Doppel (PRND) is a paralogue of the mammalian prion (PRNP) gene. It is abundant in testis and, unlike PRNP, it is expressed at low levels in the adult central nervous system (CNS). Besides, doppel overexpression correlates with some prion-disease pathological features, such as ataxia and death of cerebellar neurons. Recently, ectopic expression of doppel was found in two different tumor types, specifically in glial and haematological cancers. In order to address clinical important issues, PRND mRNA expression was investigated in a panel of 111 astrocytoma tissue samples, histologically classified according to the World Health Organization (WHO) criteria (6 grade I pilocytic astrocytomas, 15 grade II low-grade astrocytomas, 26 grade III anaplastic astrocytomas and 64 grade IV glioblastoma multiforme). Real-time PRND gene expression profiling, after normalisation with GAPDH, revealed large differences between low (WHO I and II) and high grade (III and IV) of malignancy (P<0.001). Extensive differences in PRND gene expression were also found within each grade of malignancy, suggesting that PRND mRNA quantitation might be useful to distinguish astrocytoma subtypes, and important in disease stratification and in the assessment of specific treatment strategies.

Low birth weight or diagnosis, which is a higher risk?--A meta-analysis of observational studies

Published experience with surgical treatment of newborns with low birth weight and congenital heart disease is circumscribed to isolated single case reports and a limited number of case-series. To better assess the risks of early surgical treatment and its relationship to weight and diagnosis we performed a meta-analysis of observational studies, limited to those from which data on individual patients could be extrapolated. A search on the subject in peer-reviewed journals published between 1993 and 2004 limited the number of studies, according to our restrictive criteria, to six articles. Our own series of 37 patients was added to the body of data collected in the meta-analyses. Data on 356 individually identified patients was extracted from the articles. Median weight was 2.05 kg (range 1.1-2.5) and median gestational age was 34.2 weeks (range 26-42). Overall surgical survival was 83.9% but survival was higher when a full repair was done (86.1%). According to our analysis, diagnosis was the most significant predictor of mortality (p = 0.001). Other important predictors were the presence of a surgical complication (p = 0.01), palliative surgery (p = 0.03) and the need for reoperation during the same admission (p = 0.03). We concluded that similarly to larger newborns, diagnosis in this group of patients is the most important predictor of mortality. Independently of patient's weight a full anatomic and physiologic repair is justified in most cases.

A proposed alternative mechanism of action for transmyocardial revascularization prefaced by a review of the accepted explanations

Laser transmyocardial revascularization, a procedure originally intended to simulate the perfusion mechanism of the reptilian heart, has evolved into an effective but poorly understood treatment for angina when traditional revascularization is not an option. Herein, we review the explanations that have been proposed over the years and suggest a new one. We hypothesize that the long-term mechanism of action of transmyocardial revascularization is the redistribution of stresses on the ventricular wall through the creation of fibrous transmyocardial scars, which penetrate the various layers of muscle that surround the left ventricular cavity. The stress redistribution of a load in an otherwise unchanged ventricular wall reduces the wall stress per unit of wall volume, which in turn decreases the workload for the hyperkinetic compensating areas. This reduces both oxygen demand and local metabolite production, lowering the level of angina.

[Intestinal intussusception: easy diagnosis in the 21st Century? Outcome of five years experiences]

Intussusception is an entity well codify in pediatric surgery, with guidelines well defined since years in terms of imaging and procedures.

MATERIAL

From January '99 to Dec. '03, 25 children were admitted to the Department of Pediatric Surgery of the Children's Hospital of Milan. All the aspects related to the pathology have been evaluated in the study.

RESULTS

25 patients have been studied. 23/25 presented severe pain, 19/25 normal bowel movements in the last 3 hours and in 9/25 a mass were detected at clinical examination.19/25 were submitted to laparotomy after failure of reduction through barium enema, and in 17/19 a manual reduction were performed. Only 2 patients required a bowel resection with primary anastomosis. The analysis of the delay of diagnosis, the delta-T between beginning of the symptoms and first medical evaluation was of 16,23 h. (3-72), and the delta-T between the first evaluation and diagnosis was 18,7 h. The interval between diagnosis and surgery was of 4,3.

CONCLUSION

Authors believe that intussusception still represent a challenge for medical and surgical emergency team, supported by the data in literature. Imaging procedures must not be constricted in case of minimal suspicions of intestinal intussusception.

Effects of exogenous propylene on softening, glycosidase, and pectinmethylesterase activity during postharvest ripening of apricots

Apricots (Prunus armeniaca L. cv. Boccuccia spinosa) picked at the commercial ripening stage [soluble solids content (SSC) 12.6%] were left to reach full ripening in continuously humidified air at 20 degrees C. Changes in the rate of ethylene production, firmness, soluble solids concentration, and titratable acidity were measured. The alpha-D- and beta-D-glucosidases, alpha-L-arabinofuranosidase, alpha-D- and beta-D-galactosidases, beta-D-xylosidase, and alpha-D-mannosidase activities were assayed. To evaluate the influence of ethylene on glycosidase activity, propylene (500 microL x L(-1)) was applied to apricots for 24 and 48 h. In apricots ripened in air, ethylene production increased on the first day and exhibited a typical climacteric pattern. Good edible quality was reached in 5 days when SSC was at least 14% and acidity was between 1.1 and 1.2% (% malic acid). During postharvest ripening, alpha-L-arabinofuranosidase activity increased from 1.9 to 11.6 nkat until day 7. alpha-D-Galactosidase, alpha-D-mannosidase, and beta-D-galactosidase activity increased continuously but at a lower rate. beta-D-Xylosidase activity also increased, but the level of activity was lower than the other glycosidases assayed. Pectinmethylesterase (PME) decreased during the postharvest ripening, and propylene enhanced this pattern, by stimulating ethylene production. Even the activities of alpha-L-arabinofuranosidase, beta-D-xylosidase, alpha-D-mannosidase, and beta-D-galactosidase were greatly stimulated by the propylene treatment, which consequently induced rapid softening of the fruits.

Reversible pulmonary trunk banding with a balloon catheter: assessment of rapid pulmonary ventricular hypertrophy

OBJECTIVE

We sought to assess the rapid hypertrophy of the right ventricle of young goats submitted to progressive pressure load by a balloon catheter.

METHODS

The hearts of 6 young goats were assessed by means of echocardiography and cell morphology during and after right ventricular hypertrophy had been produced by a balloon catheter. Myocardial samples of the right ventricular outflow tract were harvested for microscopic studies. The external diameter of longitudinally sectioned myocytes was measured at the nucleus level. The volume density of mitochondria was also determined. A balloon catheter was then placed through the right ventricular outflow tract in the pulmonary trunk and progressively inflated every 2 days. Postoperative serial echocardiography was performed at intervals of 1 to 2 days. The animals were killed after 2 to 3 weeks of right ventricular training for morphologic analysis.

RESULTS

Under optical microscopy, there was a 20.5% increase in the mean diameter of the myocyte of the trained right ventricle. However, under electron microscopy, there was no significant change in the mean volume density of mitochondria from the trained right ventricle. Serial echocardiography showed equalization of the ventricular thickness over a short interval of 6 to 10 days of progressive balloon inflation.

CONCLUSIONS

The balloon catheter permits the manipulation of the pressure load over the right ventricle, causing rapid hypertrophy in a 6- to 10-day period. This study suggests that nonsurgical preparation of the "pulmonary ventricle" in patients with transposition of great arteries with intact ventricular septum beyond the neonatal period could probably be accomplished within a very few days.

Antimitotic effects of usnic acid on different biological systems

Usnic acid is a biosynthesis product characteristic of several epiphytic lichens such as Evernia, Cladonia and Parmelia. Usnic acid has several interesting biological properties. It is an antibiotic and it also seems to exert an antimitotic action. It has even been postulated that usnic acid can play a role as an environmental indicator, since its concentration varies according to the presence of toxic agents. A series of tests have been run on different biological systems such as fungi, yeasts, plant cells and neoplastic human cell cultures in order to make a general evaluation of the properties of usnic acid and to highlight any analogy between its effects on phylogenetically distant organisms. The results obtained confirm some of the already known properties of usnic acid and identify concentration ranges that are active against cells from different organisms. Furthermore, at low concentrations, the acid displays a capacity to stimulate cell metabolism in some of the biological systems tested.

Oligogalacturonides Prevent Rhizogenesis in rolB-Transformed Tobacco Explants by Inhibiting Auxin-Induced Expression of the rolB Gene

Oligogalacturonides elicit several defense responses and regulate different aspects of growth and development in plants. Many of the development-related effects of oligogalacturonides appear to be amenable to an auxin antagonist activity of these oligosaccharins. To clarify the role of oligogalacturonides in antagonizing auxin, we analyzed their effect on root formation in leaf explants of tobacco harboring the plant oncogene rolB. We show here that oligogalacturonides are capable of inhibiting root morphogenesis driven by rolB in transgenic leaf explants when this process requires exogenous auxin. Because rolB expression is induced by auxin and dramatically alters the response to this hormone in transformed plant cells, the inhibiting effect of oligogalacturonides could be exerted on the induction of rolB and/or at some other auxin-requiring step(s) in rhizogenesis. We show that oligogalacturonides antagonize auxin primarily because they strongly inhibit auxin-regulated transcriptional activation of a rolB-[beta]-glucuronidase gene fusion in both leaf explants and cultured leaf protoplasts. In contrast, oligogalacturonides do not inhibit rhizogenesis when rolB transcriptional activation is made independent of auxin, as shown by the lack of inhibition of root formation in leaf explants containing rolB driven by a tetracycline-inducible promoter.

rol genes of Agrobacterium rhizogenes cucumopine strain: sequence, effects and pattern of expression

By sequencing the central region of the cucumopine-type T-DNA of Agrobacterium rhizogenes strain 2659, we identified three open reading frames homologous, to different extents, to ORFs 10, 11 and 12 (rolA, B and C) of the agropine-type (1855) T-DNA. Recombinant Agrobacterium strains encompassing the ORFs of 2659 T-DNA--which we refer to as rol alpha, beta and gamma--were utilized to infect carrot discs and to obtain transgenic tobacco plants, in order to compare the morphogenetic capabilities to those of the 1855 rol genes. Moreover, a long segment of the 5' non-coding region of rol alpha and rol beta was fused to the GUS reporter gene and the pattern of expression and the responsiveness to auxin of the constructs was analysed in transgenic tobacco. Differences in the auxin requirement for root induction between the 2659 rol genes and their respective 1855 counterparts were pinpointed. These differences are not due to gene regulation and presumably reflect functional differences in the proteins encoded. Differences were also observed in the pattern of expression of rol beta in roots of transgenic plants, as compared to rolB. In addition, the pattern of expression of rol alpha-GUS construct in roots was found to be analogous to that observed for a construct driven by two of the five regulatory domains of the rolB promoter.

Expression in different populations of cells of the root meristem is controlled by different domains of the rolB promoter

Selective gene expression in different populations of cells of the root apex of transgenic tobacco could be evidenced by means of GUS constructs with deletions of the rolB promoter and fusions with the CaMV 35S minimal promoter. Five regulatory regions have been broadly identified in the rolB 5' non-coding region. The presence of all five domains (A to E) directs gene expression in the root cap, in the protoderm and in the different tissues within the root meristematic region: the dermatocalyptrogen, the cortex and the vascular cylinder. Deletion of domain A (-623 to -471) selectively suppresses expression in non-meristematic cells, i.e. the root cap and the protoderm. Deletion of either domain B (-341 to -306) or E (80 bp around the TATA box) causes loss of expression in all cells of the root apex: constructs C + D + E, B + C + D, B + C are inactive. Domain D (70 bp around the CAAT box) is necessary for gene expression in the dermatogen and in meristematic cells of the cortex but not in the innermost meristematic layer: construct B + C + E is active only in vascular meristematic cells. Domain C (-216 to -158) seems to have a double regulatory role as construct B + E is no longer expressed in meristematic cells of the vascular cylinder but is very active in the protoderm. Constructs allowing gene expression in meristematic cells are also inducible by auxin in leaf protoplasts, while activation of the regulatory elements necessary for gene expression in the non-meristematic cells of the root apex do not seem to depend upon the hormone. The connection between auxin induction and meristematic expression is discussed.

Bacterial plant oncogenes: the rol genes' saga

The rol genes are part of the T-DNA which is transferred by Agrobacterium rhizogenes in plant cells, causing neoplastic growth and differentiation. Each of these bacterial oncogenes deeply influences plant development and is finely regulated once transferred into the plant host. Both from the study of the effects and biochemical function of the rol genes and from the analysis of their regulation, important insight in plant development can be derived. Some of the most intriguing aspects of past, current and future research on this gene system are highlighted and discussed.

Different promoter regions control level and tissue specificity of expression of Agrobacterium rhizogenes rolB gene in plants

Expression of the rolB gene of A. rhizogenes T-DNA triggers root differentiation in transformed plant cells. In order to study the regulation of this morphogenetic gene, the GUS reporter gene was placed under the control of several deleted fragments of the rolB 5' non-coding region: carrot disc transformations and the analysis of transgenic tobacco plants containing these constructions identified the presence of distinct regulatory domains in the rolB promoter. Two regions (located from positions -623 to -471 and from -471 to -341, from the translation start codon) control the level but not the tissue specificity of rolB expression: progressive deletions of the rolB promoter starting from position -1185 to -341, although at different levels, maintained the same pattern of GUS expression-maximal in root meristems and less pronounced in the vascular tissue of aerial organs. Further deletion of 35 bp, from -341 to -306, drastically affected tissue specificity: GUS activity was still clearly detectable in the vascular tissue of the aerial organs while expression in the root meristem was totally suppressed. Analysis of transgenic embryos and seedlings confirmed that distinct promoter domains are responsible for meristematic (root) and differentiated (vascular) expression of rolB. Finally, we present data concerning the effects of plant hormones on the expression of rolB-GUS constructions.

Induction and growth properties of carrot roots with different complements of Agrobacterium rhizogenes T-DNA

Single and multiple infections of carrot discs were carried out with Agrobacterium strains harbouring different segments of pRi1855 TL-DNA cloned in the binary vector Bin 19 and with a strain carrying the TR-DNA from the same Ri plasmid. Roots induced by the various co-inoculations were cultured and their growth patterns were followed. Abundant roots could be induced by TL-DNA rol genes A, B and C as a single insert (rolA + B + C) and by rolB alone provided an extended segment beyond its 5' non-coding region was included in the construction. A depression of rooting capability was caused by the inclusion of rolC together with rolB (rolB + C). In all cases co-inoculation with the Agrobacterium carrying TR-DNA-borne auxin genes was necessary for root induction since none of the rol constructions was in itself capable of eliciting any response; an exceeding majority of these roots were however shown to contain rol genes but no TR-DNA. Rooting was also elicited if rol constructions were co-inoculated with a strain carrying TL-DNA genes 13 and 14 (ORF13 + 14) instead of the TR-DNA strain. These roots were shown to contain both rol genes and ORF13 + 14. Striking differences in growth properties were shown by roots containing different complements of TL-DNA genes. Typical hairy root traits, high growth rate, branching and, most noticeably, absence of geotropism, were shown by roots containing rolB alone, while roots with rolA + B + C were geotropic as normal carrot roots. Hairy root traits were conferred to rolA + B + C roots by the concomitant presence of ORF13 + 14 and by the addition of auxin to the culture medium. A model is presented which attempts to rationalize the growth patterns by assigning interplaying roles to the various TL-DNA genes involved.

Morphogenesis and Auxin Sensitivity of Transgenic Tobacco with Different Complements of Ri T-DNA

Leaf explants of hairy root tobacco (Nicotiana tabacum) regenerants characteristically differentiate roots from the wound margins on hormonefree medium. The same response can be elicited on normal tobacco by culturing the explants in the presence of auxin. We show here that the spontaneous rooting of transformed plants is neither due to the activity of right T-DNA-borne auxin genes nor to a substantially altered balance of endogenous hormones. Rather, an increased sensitivity to auxin is conferred to transformed cells by the left T-DNA (TL-DNA). Analysis of the morphogenetic behavior of transgenic tobacco plants obtained by transferring segments of TL-DNA cloned in a binary vector system allowed us to pinpoint TL-DNA genes responsible for this increased auxin sensitivity of hairy root tissues. Three genes (open reading frames 10, 11, 12) are responsible for the spontaneous rooting of leaf explants and confer to transgenic plants an exaggerated response to auxin.

Agrobacterium rhizogenes T-DNA genes capable of inducing hairy root phenotype

Segments of the TL-DNA of the agropine type Ri plasmid pRi 1855 encompassing single and groups of open-reading frames were cloned in the Ti plasmid-derived binary vector system Bin 19. Leaf disc infections on Nicotiana tabacum led to transformed plants, some of which showed typical hairy root phenotypes, such as the wrinkled leaf morphology, excessive and partially non geotropic root systems and the ability of leaf explants to differentiate roots in a hormone-free culture medium. Particularly interestingly, most of these traits were shown by plants transformed with a TL-DNA segment encompassing the single ORF 11, corresponding to the rolB locus. Hairy root can be induced by this latter T-DNA segment on wounded stems of tobacco plants; hairy root induction on carrot discs requires, on the contrary, a more complex complement of TL-DNA genes.

Identification of the genetic locus responsible for non-polar root induction by Agrobacterium rhizogenes 1855

Root proliferation can be induced by Agrobacterium rhizogenes on carrot discs both on the apical and basal surface (facing the root apex and base, respectively) or on the apical surface only, depending on the bacterial strain. This differential response on the two surfaces is denominated polarity. We correlate the polarity of some strains with the absence of an Ri plasmid genetic locus, present in non polar strains such as A. rhizogenes 1855, which bears sequence homology with the auxin genes of Ti plasmid T-DNA. We demonstrate that this locus is responsible for root induction on the basal surface since insertion of a transposon in this region of pRi1855 induces polarity in this strain.

Localization of agropine-synthesizing functions in the TR region of the root-inducing plasmid of Agrobacterium rhizogenes 1855

The region of the Ri plasmid pRi 1855 that encodes agropine synthesis has been identified through its sequence homology with the equivalent genes of the octopine Ti plasmid pTi ACH5. Interestingly the agropine genes lie outside the so-far identified T-DNA of pRi 1855, and are separated from this latter by a long sequence of non integrated plasmid DNA. The presence of this additional T-DNA (TRight DNA) in hairy roots was demonstrated by Southern blot analysis and by the presence of specific transcripts. The genes for agropine synthesis are arranged in the Ri plasmid in a reversed order as compared to their orientation in the Ti plasmid pTi ACH5.

Agrobacterium tumefaciens RNA polymerase: a new purification procedure and a study of the stable binding sites on homologous deoxyribonucleic acid

RNA polymerase (RNA nucleotidyltransferase, EC 2.7.7.6) of Agrobacterium tumefaciens has been purified according to a fast and efficient procedure. The method involves only two chromatographic steps and yields a highly active enzyme. The RNA polymerase was studied with respect to the ability to bind its homologous genome. A. tumefaciens deoxyribonucleic acid (DNA) binds the enzyme even when fragmented at undergenic size (300 base pairs). The general binding is unspecific and very labile at low concentrations of heparin (0.66 micrograms/mL). The number and distribution of the stable binding sites, class A sites [Hinkle, D., & Chamberlin, M. J. (1972) J. Mol. Biol. 70, 157-185], have been calculated from the heparin-induced dissociation kinetics of binary complexes formed between the enzyme and DNA fragments of various sizes. A total of 3.5 x 10(3) class A sites (forming binary complexes with a half-life of 16.6 min) are present on A. tumefaciens genome, a large number of which show a distribution of 800-1000 base pairs. The rest have a more widely spaced distribution. The interactions between Escherichia coli RNA polymerase and the A. tumefaciens template have also been examined, and it has been observed that E. coli holoenzyme forms stable complexes with a shorter half-life and recognizes a lower number of class A sites on A. tumefaciens genome.