Sayanika Devi Waikhom

Erratum: Secretome weaponries of Cochliobolus lunatus interacting with potato leaf at different temperature regimes reveal a CL[xxxx]LHM - motif.

BackgroundPlant and animal pathogenic fungus Cochliobolus lunatus cause great economic damages worldwide every year. C. lunatus displays an increased temperature dependent-virulence to a wide range of hosts. Nonetheless, this phenomenon is poorly understood due to lack of insights on the coordinated secretome weaponries produced by C. lunatus under heat-stress conditions on putative hosts. To understand the mechanism better, we dissected the secretome of C. lunatus interacting with potato (Solanum tuberosum L.) leaf at different temperature regimes.ResultsC. lunatus produced melanized colonizing hyphae in and on potato leaf, finely modulated the ambient pH as a function of temperature and secreted diverse set of proteins. Using two dimensional gel electrophoresis (2-D) and mass spectrometry (MS) technology, we observed discrete secretomes at 20°C, 28°C and 38°C. A total of 21 differentially expressed peptide spots and 10 unique peptide spots (that did not align on the gels) matched with 28 unique protein models predicted from C. lunatus m118 v.2 genome peptides. Furthermore, C. lunatus secreted peptides via classical and non-classical pathways related to virulence, proteolysis, nucleic acid metabolism, carbohydrate metabolism, heat stress, signal trafficking and some with unidentified catalytic domains.ConclusionsWe have identified a set of 5 soluble candidate effectors of unknown function from C. lunatus secretome weaponries against potato crop at different temperature regimes. Our findings demonstrate that C. lunatus has a repertoire of signature secretome which mediates thermo-pathogenicity and share a leucine rich “CL[xxxx]LHM”-motif. Considering the rapidly evolving temperature dependent-virulence and host diversity of C. lunatus, this data will be useful for designing new protection strategies.

Scanning electron microscopy of pollen structure throws light on resolving Bambusa–Dendrocalamus complex: bamboo flowering evidence

Since the introduction of the new genus Sinocalamus in 1940 which is now dissociated into Bambusa and Dendrocalamus, molecular markers have long been unable to discern members of the Bambusa–Dendrocalamus complex. Rapid concerted evolution governed by high level of transition/transversion at the noncoding DNA regions has limited the ability of internal transcribed spacer (rDNA) and trnL-F intergenic spacer to resolve Bambusa and Dendrocalamus in phylogenetic analysis. Based on scanning electron microscopy (SEM) analysis of Bambusa vulgaris and Dendrocalamus manipureanus pollen development, we provided the evidence that there exists genus specificity in the development and structure of woody bamboo pollen which can serve as a benchmark for allocated new species into the genus Bambusa and Dendrocalamus substantiating molecular data.

Host-Range Dynamics of Cochliobolus lunatus: From a Biocontrol Agent to a Severe Environmental Threat

We undertook an investigation to advance understanding of the host-range dynamics and biocontrol implications of Cochliobolus lunatus in the past decade. Potato (Solanum tuberosum L) farms were routinely surveyed for brown-to-black leaf spot disease caused by C. lunatus. A biphasic gene data set was assembled and databases were mined for reported hosts of C. lunatus in the last decade. The placement of five virulent strains of C. lunatus causing foliar necrosis of potato was studied with microscopic and phylogenetic tools. Analysis of morphology showed intraspecific variations in stromatic tissues among the virulent strains causing foliar necrosis of potato. A maximum likelihood inference based on GPDH locus separated C. lunatus strains into subclusters and revealed the emergence of unclustered strains. The evolving nutritional requirement of C. lunatus in the last decade is exhibited by the invasion of vertebrates, invertebrates, dicots, and monocots. Our results contribute towards a better understanding of the host-range dynamics of C. lunatus and provide useful implications on the threat posed to the environment when C. lunatus is used as a mycoherbicide.

Cochliobolus lunatus colonizes potato by adopting different invasion strategies on cultivars: New insights on temperature dependent-virulence

Extreme temperature fluctuations affect the interaction dynamics of Cochliobolus lunatus through temperature-dependent virulence, virulence differentiation and induced-virulence which poses a major threat to global food security. The relationship between higher temperature and pathogenicity of C. lunatus on reported hosts are poorly understood. In this study, temperature stress was applied on C. lunatus to investigate the correlation among the different types of conidia. Additionally, a comparative dissection of the invasion process, infection structures and conidial germination pattern on four different Solanum tuberosum L. (potato) cultivars were performed. Based on microscopic examination, it was found that C. lunatus adopts different hyphae morphology and septation pattern at different temperature regimes and produce different types of conidia. The study showed that four-celled conidia are overproduced at elevated temperature (>30 °C) than one, two, three and five-celled conidia. Our finding revealed that C. lunatus conidia exhibit bipolar germination (>14.67%, P<0.05), unipolar germination (>35.33%, P<0.05), penetrate subcutaneously via epidermal anticlinal cell wall (>0.33%, P < 0.05) and differentially form appressoria-like structures during colonization of four different potato cultivars. Importantly, it is shown that unipolar germination and bipolar germination in C. lunatus are independently occurring phenomenon irrespective of the host. It is confirmed that C. lunatus adopt different but highly successful strategies on four different potato cultivars to incite brown-to-black leaf spot disease. Altogether, our data showed that increase in temperature enhances C. lunatus virulence on different potato cultivars irrespective of their inherent thermotolerant traits.

Grappling the high altitude for safe edible bamboo shoots with rich nutritional attributes and escaping cyanogenic toxicity.

Consumption of bamboo species with high level of total cyanogenic content (TCC) in Asia by many ethnic groups is significantly associated with food poisoning and occasionally Konzo (a neurological disorder). Adequate characterization of edible bamboo species with low level of TCC and high nutritious attributes is required for consumers safety as well as for the conservation of the gene pool. Here, we employed morphological descriptors, atomic absorption spectrophotometer, RAPD, and trnL-F intergenic spacer to characterize 15 indigenous edible bamboo species of north-east India. The study indicates that morphologically and genetically evolved edible bamboo species having large and robust bamboo-shoot texture and growing at low altitude contain high level of TCC, low antioxidant properties, and low levels of beneficial macronutrients and micronutrients. Importantly, Dendrocalamus species are shown to be rich in TCC irrespective of the growing altitude while Bambusa species are found to have moderate level of TCC. The findings clearly demonstrated that Chimonobambusa callosa growing at high altitude represents safe edible bamboo species with nutritious attributes.

An Effective Protocol for Micropropagation of Edible Bamboo Species (Bambusa tulda and Melocanna baccifera) through Nodal Culture

High demand for edible bamboo shoots of Bambusa tulda and Melocanna baccifera in many Asian ethnic groups has led to the need for developing intensive bamboo farming. To achieve this, in vitro regeneration of bamboo plantlets is needed due to the long and irregular bamboo flowering cycle and scarcity of bamboo seeds. An effective protocol for plantlets regeneration in B. tulda and M. baccifera from nodal explants following validation of the species using the sequence of trnL-F intergenic spacer region is described. Effective axillary bud breaking was achieved at 3 mg/L of 6-benzylaminopurine (BAP) in MS medium. Importantly, combining 2 mg/L of kinetin (Kn) with 3 mg/L of BAP produced a synergistic effect for shoot multiplication in B. tulda and M. baccifera. Under optimized conditions in half-strength MS medium supplemented with 3 mg/L of indole-3-butyric acid (IBA), 10 mg/L of coumarin, and 3% sucrose, profuse production of dark-brown rhizome in B. tulda and abundant rooting (81.67%, P < 0.05, F = 15.46) for M. baccifera within 30 days were achieved. The established protocol and the validation of the reported species at the molecular level will be of help to stakeholders in edible bamboo trade to conserve gene-pool and increase productivity.

Biotrophic interaction of Sporisorium scitamineum on a new host--Saccharum spontaneum.

Sporisorium scitamineum is a biotrophic smut fungus harbored inside the smut gall on the top internodal region of Saccharum spontaneum, a wild relative of sugarcane (Saccharum officinarum). The interactions of spined conidia of S. scitamineum with S. spontaneum were examined during the different stages of plant growth starting from the bud stage to the decaying stage. The spores in the soil from the polyetic inocula grew into confined epidermal cells of the buds and finally sporulated in the topmost internodal region. Hyphae invasion of the plant tissues were restricted to the point of infection. Culms of infected plants in late October sporulated, notably; hyphal sporulation produced shorter hyphal stolons. Remarkably, the nodal regions of infected plants had no spores and fragmented hyphae. On the basis of microscopic analyses, hyphae and spores were absent in all internodes above the ground till the topmost smut gall region. This result indicated that, S. scitamineum undergoes tissue-confined invasion of S. spontaneum. By associating culture medium method with polymerase chain reaction (PCR) on plant portions void of smut gall, S. scitamineum was not detected, indicating that colonization was not systemic. It was observed that the biotrophic interaction resulted in structural reorganization in the restricted region of infection forming erect cylindrical structure, in which the fungus was sandwiched between the central stalk and sheath, and possibly played a key role in preventing inflorescence. Comparatively, a significant difference in the rate of teliospores germination between reference Ustilago esculenta (26.6%, P<0.05) and S. scitamineum (62.9%, P<0.05) at 20° C was observed. This study also provides insights on the effect of different temperature regimes on the germination of S. scitamineum teliospores in vitro.

Virus tolerance and recovery from viral induced-symptoms in plants are associated with transcriptome reprograming

Plant recovery from viral infection is characterized by initial severe systemic symptoms which progressively decrease, leading to reduced symptoms or symptomless leaves at the apices. A key feature to plant recovery from invading nucleic acids such as viruses is the degree of the host’s initial basal immunity response. We review current links between RNA silencing, recovery and tolerance, and present a model in which, in addition to regulation of resistance (R) and other defence-related genes by RNA silencing, viral infections incite perturbations of the host physiological state that trigger reprogramming of host responses to by-pass severe symptom development, leading to partial or complete recovery. Recovery, in particular in perennial hosts, may trigger tolerance or virus accommodation. We discuss evidence suggesting that plant viruses can avoid total clearance but persistently replicate at low levels, thereby modulating the host transcriptome response which minimizes fitness cost and triggers recovery from viral-symptoms. In some cases a susceptible host may fail to recover from initial viral systemic symptoms, yet, accommodates the persistent virus throughout the life span, a phenomenon herein referred to as non-recovery accommodation, which differs from tolerance in that there is no distinct recovery phase, and differs from susceptibility in that the host is not killed. Recent advances in plant recovery from virus-induced symptoms involving host transcriptome reprogramming are discussed.

Current trends in outwitting resistance development in Candida infections through photodynamic and short peptide therapies: a strategic-shift from conventional antifungal agents.

Abstract Disequilibrium in the human debilitated immune system favors proliferation of invasive Candida species, a major therapeutic challenge due to development of resistance to several conventional antifungal agents (CAA) worldwide. Multiple mutations observed at specific loci that are targets for CAA are recognized as sources of drug resistance. This has prompted a shift from CAA, to diverse combination therapies, photodynamic and short peptide therapies capable of triggering specific apoptotic reactions within candidal cells. In this review, new designs and combination of short peptide (SP) with CAA as well as current application of photodynamic inactivation (PDI) against Candida species geared at generating reactive species of oxygen (ROS) and nitrogen (RNS) are discussed. It is observed that oxidative and nitrosative stresses provides a superior broad candidacidal effects for eradication of drug-resistant Candida species. The mechanism and limitations in these strategic approaches over CAA is also discussed.

Invasive Aspergillus terreus morphological transitions and immunoadaptations mediating antifungal resistance

Background and aims Aspergillus terreus Thom is a pathogen of public health and agricultural importance for its seamless abilities to expand its ecological niche. The aim of this study was holistically to investigate A. terreus morphological and immunoadaptations and their implication in antifungal resistance and proliferation during infection. Materials and methods In-depth unstructured mining of relevant peer-reviewed literature was performed for A. terreus morphological, immune, resistance, and genetic diversity based on the sequenced calmodulin-like gene. Results Accessory conidia and phialidic conidia produced by A. terreus confer discrete anti-fungal resistance that ensures survivability during therapies. Interestingly, by producing unique metabolites such as Asp–melanin and terretonin, A. terreus is capable of hijacking macrophages and scavenging iron, respectively. As such, A. terreus has established a rare mechanism to mitigate phagocytosis and swing the interaction dynamics in favor of its proliferation and survival in hosts. Conclusion It is further unraveled that besides A. terreus genetic diversity, morphological, biochemical, and immunologic adaptations associated with conidia germination and discharge of chemical signals during infection enable masking of the host defense as an integral part of its strategy to survive and rapidly colonize hosts.