Bioprospecting desert plant Bacillus endophytic strains for their potential to enhance plant stress tolerance

Plant growth-promoting bacteria (PGPB) are known to increase plant tolerance to several abiotic stresses, specifically those from dry and salty environments. In this study, we examined the endophyte bacterial community of five plant species growing in the Thar desert of Pakistan. Among a total of 368 culturable isolates, 58 Bacillus strains were identified from which the 16 most divergent strains were characterized for salt and heat stress resilience as well as antimicrobial and plant growth-promoting (PGP) activities. When the 16 Bacillus strains were tested on the non-host plant Arabidopsis thaliana, B. cereus PK6-15, B. subtilis PK5-26 and B. circulans PK3-109 significantly enhanced plant growth under salt stress conditions, doubling fresh weight levels when compared to uninoculated plants. B. circulans PK3-15 and PK3-109 did not promote plant growth under normal conditions, but increased plant fresh weight by more than 50% when compared to uninoculated plants under salt stress conditions, suggesting that these salt tolerant Bacillus strains exhibit PGP traits only in the presence of salt. Our data indicate that the collection of 58 plant endophytic Bacillus strains represents an important genomic resource to decipher plant growth promotion at the molecular level.

Root endodermal barrier system contributes to defence against plant-parasitic cyst and root-knot nematodes

Plant-parasitic nematodes (PPNs) cause tremendous yield losses worldwide in almost all economically important crops. The agriculturally most important PPNs belong to a small group of root-infecting sedentary endoparasites that includes cyst and root-knot nematodes. Both cyst and root-knot nematodes induce specialized long-term feeding structures in root vasculature from which they obtain their nutrients. A specialized cell layer in roots called the endodermis, which has cell walls reinforced with suberin deposits and a lignin-based Casparian strip (CS), protects the vascular cylinder against abiotic and biotic threats. To date, the role of the endodermis, and especially of suberin and the CS, during plant-nematode interactions was largely unknown. Here, we analyzed the role of suberin and CS during interaction between Arabidopsis plants and two sedentary root-parasitic nematode species, the cyst nematode Heterodera schachtii and the root-knot nematode Meloidogyne incognita. We found that nematode infection damages the endodermis leading to the activation of suberin biosynthesis genes at nematode infection sites. Although feeding sites induced by both cyst and root-knot nematodes are surrounded by endodermis during early stages of infection, the endodermis is degraded during later stages of feeding site development, indicating periderm formation or ectopic suberization of adjacent tissue. Chemical suberin analysis showed a characteristic suberin composition resembling peridermal suberin in nematode-infected tissue. Notably, infection assays using Arabidopsis lines with CS defects and impaired compensatory suberization, revealed that the CS and suberization impact nematode infectivity and feeding site size. Taken together, our work establishes the role of the endodermal barrier system in defence against a soil-borne pathogen.

Re-targeting of a plant defense protease by a cyst nematode effector

Plants mount defense responses during pathogen attacks, and robust host defense suppression by pathogen effector proteins is essential for infection success. 4E02 is an effector of the sugar beet cyst nematode Heterodera schachtii. Arabidopsis thaliana lines expressing the effector-coding sequence showed altered expression levels of defense response genes, as well as higher susceptibility to both the biotroph H. schachtii and the necrotroph Botrytis cinerea, indicating a potential suppression of defenses by 4E02. Yeast two-hybrid analyses showed that 4E02 targets A. thaliana vacuolar papain-like cysteine protease (PLCP) 'Responsive to Dehydration 21A' (RD21A), which has been shown to function in the plant defense response. Activity-based protein profiling analyses documented that the in planta presence of 4E02 does not impede enzymatic activity of RD21A. Instead, 4E02 mediates a re-localization of this protease from the vacuole to the nucleus and cytoplasm, which is likely to prevent the protease from performing its defense function and at the same time, brings it in contact with novel substrates. Yeast two-hybrid analyses showed that RD21A interacts with multiple host proteins including enzymes involved in defense responses as well as carbohydrate metabolism. In support of a role in carbohydrate metabolism of RD21A after its effector-mediated re-localization, we observed cell wall compositional changes in 4E02 expressing A. thaliana lines. Collectively, our study shows that 4E02 removes RD21A from its defense-inducing pathway and repurposes this enzyme by targeting the active protease to different cell compartments.

Single-cell damage elicits regional, nematode-restricting ethylene responses in roots

Plants are exposed to cellular damage by mechanical stresses, herbivore feeding, or invading microbes. Primary wound responses are communicated to neighboring and distal tissues by mobile signals. In leaves, crushing of large cell populations activates a long-distance signal, causing jasmonate production in distal organs. This is mediated by a cation channel-mediated depolarization wave and is associated with cytosolic Ca²⁺ transient currents. Here, we report that much more restricted, single-cell wounding in roots by laser ablation elicits non-systemic, regional surface potential changes, calcium waves, and reactive oxygen species (ROS) production. Surprisingly, laser ablation does not induce a robust jasmonate response, but regionally activates ethylene production and ethylene-response markers. This ethylene activation depends on calcium channel activities distinct from those in leaves, as well as a specific set of NADPH oxidases. Intriguingly, nematode attack elicits very similar responses, including membrane depolarization and regional upregulation of ethylene markers. Moreover, ethylene signaling antagonizes nematode feeding, delaying initial syncytial-phase establishment. Regional signals caused by single-cell wounding thus appear to constitute a relevant root immune response against small invaders.

Abstract P3-03-03: Sentinel node biopsy (SNB) vs Low axillary sampling (LAS) in predicting nodal status of post-chemotherapy axilla in women with breast cancer

Introduction

There is no safe method of avoiding complete axillary lymph node dissection in women with breast cancer after neo-adjuvant chemotherapy. sentinel node biopsy (SNB) has had prohibitively high false negative rate. We tested low axillary sampling (LAS) and SNB performed in same patient to predict axillary lymph node status in clinically node negative women undergoing breast conservation or modified radical mastectomy after neo-adjuvant chemotherapy.

Methodology

Post neo-adjuvant chemotherapy 751 women who had no palpable axillary lymph node underwent LAS (all lymph nodes below intercosto-brachial nerve). Of these 751 women, 730 also underwent SNB by dual technique after injection of blue dye as well as radio-isotope. SN was identified within and outside axillary sampling specimen. SN as well as LAS specimens were distinctly examined for nodal metastasis. The rest of the axillary dissection was completed in all patients. Post NACT 292/751(38.9%) had residual positive lymph nodes on pathology. The identification rate, false negative rate (FNR), and negative predictive value (NPV) of SNB and LAS were compared for predicting negative axillary lymph node status.

Results

The median clinical tumor size was 5cm (1-15cm) and 533(71%) patients were N1 or N2 at presentation. The SNB identification rate was 87.1% (636 of 730), with a median of 5 nodes and node positive in 238 of 636 (37.4%). LAS identification rate was 98% (736 of 751), with a median of 7 nodes and node positive in 292 of 736 (39.6%). In all but one case, the SN was found within the LAS specimen. The FNR of SNB (blue, hot and adjacent palpable nodes) was 19.7% (47 of 238, one sided 95% upper CI 24.0) compared to LAS with FNR of 9.9% (29 of 292, one-sided 95% upper CI 12.8) (p<0.001). Comparative NPV for SNB and LAS were 89.4% and 93.9% respectively. If SNB was confined to blue/hot node excluding adjacent palpable nodes, FNR was 31.6% (74 of 234, 95% upper CI 36.6).

Conclusions

LAS is superior to SNB in identification rate, FNR and NPV in predicting node negative axilla post-neoadjuvant chemotherapy. LAS can be safely used to predict negative axilla with less than 10% chance of leaving residual disease.

Citation Format: Parmar V, Nair NS, Vanamali V, Hawaldar RW, Siddique S, Shet T, Desai SB, Rangarajan V, Patil A, Gupta S, Badwe RA. Sentinel node biopsy (SNB) vs Low axillary sampling (LAS) in predicting nodal status of post-chemotherapy axilla in women with breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-03.

Parasitic nematodes manipulate plant development to establish feeding sites

Cyst and root-knot nematodes, the two economically most important groups of plant parasitic nematodes, induce neoplastic feeding sites in the roots of their host plants. The formation of feeding sites is accompanied by large-scale transcriptomic, metabolomic, and structural changes in host plants. However, the mechanisms that lead to such remarkable changes have remained poorly understood until recently. Now, genomic and genetic analyses have greatly enhanced our understanding of all aspects of plant-nematode interaction. Here, we review some of the recent advances in understanding cyst and root-knot nematode parasitism. In particular, we highlight new findings on the role of plant hormones and small RNAs in nematode feeding site formation and function. Finally, we touch on our emerging understanding of the function of nematode-associated secretions.

An Ancestral Allele of Pyrroline-5-carboxylate synthase1 Promotes Proline Accumulation and Drought Adaptation in Cultivated Barley

Water scarcity is a critical threat to global crop production. Here, we used the natural diversity of barley (Hordeum vulgare) to dissect the genetic control of proline (Pro) mediated drought stress adaptation. Genetic mapping and positional cloning of a major drought-inducible quantitative trait locus (QPro.S42-1H) revealed unique allelic variation in pyrroline-5-carboxylate synthase (P5cs1) between the cultivated cultivar Scarlett (ssp. vulgare) and the wild barley accession ISR42-8 (ssp. spontaneum). The putative causative mutations were located in the promoter of P5cs1 across the DNA binding motifs for abscisic acid-responsive element binding transcription factors. Introgression line (IL) S42IL-143 carrying the wild allele of P5cs1 showed significant up-regulation of P5cs1 expression compared to Scarlett, which was consistent with variation in Pro accumulation under drought. Next, we transiently expressed promoter::reporter constructs of ISR42-8 and Scarlett alleles in Arabidopsis (Arabidopsis thaliana) mesophyll protoplasts. GUS expression analysis showed a significantly higher activation of the ISR42-8 promoter compared to Scarlett upon abscisic acid treatment. Notably, the ISR42-8 promoter activity was impaired in protoplasts isolated from the loss-of-function abf1abf2abf3abf4 quadruple mutant. A series of phenotypic evaluations demonstrated that S42IL-143 maintained leaf water content and photosynthetic activity longer than Scarlett under drought. These findings suggest that the ancestral variant of P5cs1 has the potential for drought tolerance and understanding drought physiology of barley and related crops.

Genome-wide association study uncovers a novel QTL allele of AtS40-3 that affects the sex ratio of cyst nematodes in Arabidopsis

Plant-parasitic cyst nematodes are obligate sedentary parasites that infect the roots of a broad range of host plants. Cyst nematodes are sexually dimorphic, but differentiation into male or female is strongly influenced by interactions with the host environment. Female populations typically predominate under favorable conditions, whereas male populations predominate under adverse conditions. Here, we performed a genome-wide association study (GWAS) in an Arabidopsis diversity panel to identify host loci underlying variation in susceptibility to cyst nematode infection. Three different susceptibility parameters were examined, with the aim of providing insights into the infection process, the number of females and males present in the infected plant, and the female-to-male sex ratio. GWAS results suggested that variation in sex ratio is associated with a novel quantitative trait locus allele on chromosome 4. Subsequent candidate genes and functional analyses revealed that a senescence-associated transcription factor, AtS40-3, and PPR may act in combination to influence nematode sex ratio. A detailed molecular characterization revealed that variation in nematode sex ratio was due to the disturbed common promoter of AtS40-3 and PPR genes. Additionally, single nucleotide polymorphisms in the coding sequence of AtS40-3 might contribute to the natural variation in nematode sex ratio.

Arabidopsis HIPP27 is a host susceptibility gene for the beet cyst nematode Heterodera schachtii

Sedentary plant-parasitic cyst nematodes are obligate biotrophs that infect the roots of their host plant. Their parasitism is based on the modification of root cells to form a hypermetabolic syncytium from which the nematodes draw their nutrients. The aim of this study was to identify nematode susceptibility genes in Arabidopsis thaliana and to characterize their roles in supporting the parasitism of Heterodera schachtii. By selecting genes that were most strongly upregulated in response to cyst nematode infection, we identified HIPP27 (HEAVY METAL-ASSOCIATED ISOPRENYLATED PLANT PROTEIN 27) as a host susceptibility factor required for beet cyst nematode infection and development. Detailed expression analysis revealed that HIPP27 is a cytoplasmic protein and that HIPP27 is strongly expressed in leaves, young roots and nematode-induced syncytia. Loss-of-function Arabidopsis hipp27 mutants exhibited severely reduced susceptibility to H. schachtii and abnormal starch accumulation in syncytial and peridermal plastids. Our results suggest that HIPP27 is a susceptibility gene in Arabidopsis whose loss of function reduces plant susceptibility to cyst nematode infection without increasing the susceptibility to other pathogens or negatively affecting the plant phenotype.

Rituximab use in pediatric lupus anticoagulant hypoprothrombinemia syndrome - report of three cases and review of the literature

Lupus anticoagulant hypoprothrombinemia syndrome (LA-HPS) is a rare condition that may predispose both to thrombosis and bleeding due to positive lupus anticoagulant (LA) and factor II (FII) deficiency. It can be seen in association with infections or systemic lupus erythematosus (SLE) and may require glucocorticoids (GCs) and/or immunosuppressive medications. Pediatric LA-HPS cases in the literature and three cases that received only rituximab (RTX) for LA-HPS (in addition to GCs) at two institutions between January 2010 and June 2017 were analyzed descriptively. Pediatric LA-HPS cases (≤18 years) with bleeding or thrombotic events were included. Information obtained included demographics, presenting symptoms, diagnoses, treatments, pre-/post-treatment prothrombin time (PT)/partial thromboplastin time (PTT)/LA/FII levels, and outcomes. In addition to three LA-HPS cases identified at our institutions, as of June 2017, 37 articles reported 54 pediatric LA-HPS cases (mean age: 8 years (0.9-17 years); female/male: (2:1); viral illness 27 (50%), SLE 20 (37%), and other six (11%)). All cases had a positive LA and FII deficiency (range: 0%-40%). All cases presented with bleeding diathesis and were treated with various regimens, but there was no reported use of RTX. The purpose of this report is to describe the novel use of RTX as a steroid-sparing agent in three pediatric SLE cases and to systematically review the literature on pediatric cases of LA-HPS.

Amino acid permease 6 modulates host response to cyst nematodes in wheat and Arabidopsis

Cyst nematodes are plant parasites that cause significant crop loss in wheat and other crops. Infective juveniles invade roots and induce syncytial feeding structures as the only source of nutrients throughout their life. A previous genome-wide association study in wheat identified amino acid permease 6 (TaAAP6) to be linked to susceptibility to the cereal cyst nematode Heterodera filipjevi. To characterise the role of AAP6 during nematode parasitism, we analysed the expression of TaAAP6 and the Arabidopsis orthologue AtAAP6. TaAAP6 was found to be highly expressed in nematode-infected roots of susceptible wheat, whereas it was not upregulated in nematode-infected roots of resistant accessions. AtAAP6 was also found to be highly upregulated in nematode-induced syncytia compared with non-infected roots. Infection assays with an AtAAP6 knock-out mutant revealed reduction in developing females, female size, and size of female-associated syncytia, thus indicating the importance of AAP6 in cyst nematode parasitism.

Damage-associated responses of the host contribute to defence against cyst nematodes but not root-knot nematodes

When nematodes invade and subsequently migrate within plant roots, they generate cell wall fragments (in the form of oligogalacturonides; OGs) that can act as damage-associated molecular patterns and activate host defence responses. However, the molecular mechanisms mediating damage responses in plant-nematode interactions remain unexplored. Here, we characterized the role of a group of cell wall receptor proteins in Arabidopsis, designated as polygalacturonase-inhibiting proteins (PGIPs), during infection with the cyst nematode Heterodera schachtii and the root-knot nematode Meloidogyne incognita. PGIPs are encoded by a family of two genes in Arabidopsis, and are involved in the formation of active OG elicitors. Our results show that PGIP gene expression is strongly induced in response to cyst nematode invasion of roots. Analyses of loss-of-function mutants and overexpression lines revealed that PGIP1 expression attenuates infection of host roots by cyst nematodes, but not root-knot nematodes. The PGIP1-mediated attenuation of cyst nematode infection involves the activation of plant camalexin and indole-glucosinolate pathways. These combined results provide new insights into the molecular mechanisms underlying plant damage perception and response pathways during infection by cyst and root-knot nematodes, and establishes the function of PGIP in plant resistance to cyst nematodes.

Identification and characterization of a putative protein disulfide isomerase (HsPDI) as an alleged effector of Heterodera schachtii

The plant-parasitic nematode Heterodera schachtii is an obligate biotroph that induces syncytial feeding sites in roots of its hosts. Nematodes produce effectors that are secreted into the host and facilitate infection process. Here we identified H. schachtii protein disulphide isomerase (HsPDI) as a putative effector that interferes with the host’s redox status. In situ hybridization showed that HsPdi is specifically localized within esophageal glands of pre-parasitic second stage juveniles (J2). HsPdi is up-regulated in the early parasitic J2s. Silencing of HsPdi by RNA interference in the J2s hampers their development and leads to structural malfunctions in associated feeding sites induced in Arabidopsis roots. Expression of HsPDI in Arabidopsis increases plant’s susceptibility towards H. schachtii. HsPdi expression is up-regulated in the presence of exogenous H₂O₂, whereas HsPdi silencing results in increased mortality under H₂O₂ stress. Stable expression of HsPDI in Arabidopsis plants decreases ROS burst induced by flg22. Transiently expressed HsPDI in N. benthamiana leaves is localized in the apoplast. HsPDI plays an important role in the interaction between nematode and plant, probably through inducing local changes in the redox status of infected host tissue. It also contributes to protect the nematode from exogenous H₂O₂ stress.

Divergent expression of cytokinin biosynthesis, signaling and catabolism genes underlying differences in feeding sites induced by cyst and root-knot nematodes

Cyst and root-knot nematodes are obligate parasites of economic importance with a remarkable ability to reprogram root cells into unique metabolically active feeding sites. Previous studies have suggested a role for cytokinin in feeding site formation induced by these two types of nematodes, but the mechanistic details have not yet been described. Using Arabidopsis as a host plant species, we conducted a comparative analysis of cytokinin genes in response to the beet cyst nematode (BCN), Heterodera schachtii, and the root-knot nematode (RKN), Meloidogyne incognita. We identified distinct differences in the expression of cytokinin biosynthesis, catabolism and signaling genes in response to infection by BCN and RKN, suggesting differential manipulation of the cytokinin pathway by these two nematode species. Furthermore, we evaluated Arabidopsis histidine kinase receptor mutant lines ahk2/3, ahk2/4 and ahk3/4 in response to RKN infection. Similar to our previous studies with BCN, these lines were significantly less susceptible to RKN without compromising nematode penetration, suggesting a requirement of cytokinin signaling in RKN feeding site formation. Moreover, an analysis of ahk double mutants using CycB1;1:GUS/ahk introgressed lines revealed contrasting differences in the cytokinin receptors mediating cell cycle activation in feeding sites induced by BCN and RKN.

Factors affecting the survival following surgical treatment of chronic subdural haematoma: Single institutional experience

BACKGROUND

Chronic subdural haematoma (CSDH) is one of the most commonly treated condition in neurosurgery. It affects elderly populations who often have significant medical co-morbidities resulting in poor prognosis. The study aimed at identifying clinical factors influencing the survival following surgical management of CSDH.

METHODS

Retrospective study included 267 cases that underwent surgery for CSDH and followed over 5-year period (2010-2015); data retrieved with reference to operation details, radiology reports and discharge. Using logistic and Cox regression analysis, the patient survival data was analysed with respect to patient demographics, type of surgery, co-morbidities, anticoagulation treatment, and discharge destination.

RESULTS

The overall survival in the cohort was 37.0months (IQR: 20.0-60.0). The median age of the patients was 76years (IQR: 66-82) and the median length of hospital stay was 10days (range 1-126days; IQR: 6-17days). The recurrence rate was 6.37% (n=17). Fifty-three (19.85%) patients recorded deceased on the IPM database as of October 2016 and of those 11 died in hospital. Univariate Cox-regression analysis revealed increased age (HR: 1.80; 95%CI: 1.04-3.11), length of hospital stay (HR: 2.50; 95%CI: 1.41-4.41) and number of co-morbidities (HR: 2.19; 95%CI: 1.26-3.79) were associated with poor prognosis. Glasgow coma scale (GCS) at discharge was found to be significantly associated with survival whilst anticoagulation treatment did not. Multivariate analysis confirmed similar findings significant statistically.

CONCLUSION

Age at admission, median length of hospital stay, number of co-morbidities, GCS at discharge and discharge destination have been found to influence survival significant statistically.

Genome-Wide Association Study in Wheat Identifies Resistance to the Cereal Cyst Nematode Heterodera filipjevi

The cyst nematode Heterodera filipjevi is a plant parasite causing substantial yield loss in wheat. Resistant cultivars are the preferred method of controlling cyst nematodes. Association mapping is a powerful approach to detect associations between phenotypic variation and genetic polymorphisms; in this way favorable traits such as resistance to pathogens can be located. Therefore, a genome-wide association study of 161 winter wheat accessions was performed with a 90K iSelect single nucleotide polymorphism (SNP) chip. Population structure analysis grouped into two major subgroups and first principal component accounted 6.16% for phenotypic diversity. The genome-wide linkage disequilibrium across wheat was 3 cM. Eleven quantitative trait loci (QTLs) on chromosomes 1AL, 2AS, 2BL, 3AL, 3BL, 4AS, 4AL, 5BL, and 7BL were identified using a mixed linear model false discovery rate of P < 0.01 that explained 43% of total genetic variation. This is the first report of QTLs conferring resistance to H. filipjevi in wheat. Eight QTLs on chromosomes 1AL, 2AS, 2BL, 3AL, 4AL, and 5BL were linked to putative genes known to be involved in plant-pathogen interactions. Two other QTLs on 3BL and one QTL on 7BL linked to putative genes known to be involved in abiotic stress.

Iron Polymaltose Complex in the Treatment of Iron Deficiency Anemia in Pregnancy

Iron deficiency anaemia is a major public health problem in pregnancy. About 58% of pregnant women in developed countries are anaemic mainly due to iron deficiency resulting a serious negative consequences on children, mothers and eventually on the nation. This quasi-experimental multi centered study (Before after study) was done to evaluate the efficacy and tolerability of Iron Polymaltose Complex (IPC) in the treatment of iron deficiency anaemia and it was performed at the OPD of Bangladesh Medical College and two other clinics of Dhaka city from August 2011 to September 2013. A total of 80 (eighty) subjects were selected by purposive sampling as per inclusion and exclusion criteria. They were treated by Iron Polymaltose-IPC [47mg elemental iron + Folic Acid 0.5mg + Zinc 22.5mg - Once daily orally for 12 weeks]. At the beginning and after 12 weeks of intervention by Iron Polymaltose Complex (IPC) Hb%, Packed Cell Volume (PCV), Mean Corpuscular Volume (MCV), Mean Corpuscular Hemoglobin (MCH), Serum iron, and Serum ferritin were measured. Data were analyzed by SPSS version 13.0. Paired and unpaired 't' test was used to analyze differences within groups and between groups. Chi-square test was done to analyze primary efficacy parameters and adverse drug reactions (ADR). Most of the respondents were within the age group of 18-23 and 30-35 years (32.6% each). Significant differences were found by treatment with IPC for 12 weeks in Hb%, PCV, MCV, MCH, Serum iron, and Serum ferritin level. In iron deficiency anaemia during pregnancy IPC may be used as a safe and cost-effective therapeutic management.

Plant basal resistance to nematodes: an update

Most plant-parasitic nematodes are obligate biotrophs feeding on the roots of their hosts. Whereas ectoparasites remain on the root surface and feed on the outer cell layers, endoparasitic nematodes enter the host to parasitize cells around or within the central cylinder. Nematode invasion and feeding causes tissue damage which may, in turn, lead to the activation of host basal defence responses. Hitherto, research interests in plant-nematode interaction have emphasized effector-triggered immunity rather than basal plant defence responses. However, some recent investigations suggest that basal defence pathways are not only activated but also play an important role in determining interaction outcomes. In this review we discuss the major findings and point out future directions to dissect the molecular mechanisms underlying plant basal defence to nematodes further.