Molecular and Pathological Characterization of Colletotrichum falcatum Infecting Subtropical Indian Sugarcane

Red rot, caused by Colletotrichum falcatum, is the most significant problem of sugarcane worldwide. Pathological studies and three different marker systems were used to characterize 25 C. falcatum isolates collected from 18 subtropical sugarcane cultivars from 15 different sugarcane‐growing regions of three north‐eastern states of India to assess pathogen diversity. Of these 25 isolates, three were new (RR2A, RR15, RR83) from cultivars Co 7717, Co J83 and Co S88230, respectively, pathologically characterized on 13 standard differential hosts. Isolates Cf 01, Cf 08 and RR15 were the most, and Cf‐07 the least virulent. Molecular characterization using random amplified polymorphic DNA, universal rice primers (URP) and inter simple sequence repeat markers amplified a total of 161 alleles of which 159 were polymorphic (98.76%). Unweighted paired group method with arithmetic averages analysis of combined data of all the DNA markers obtained by three marker systems classified 25 isolates into six clusters at 34% genetic similarity with high Mantel matrix correlation (r = 0.83). The principal component analysis (PCA) of marker data explained 68% of the variation by first three components. Molecular diversity as revealed in these isolates is very high, but non‐structured. Isolate Co Pant 84212 was found to be genetically most diverse. We demonstrated for the first time that URPs derived from weed rice could successfully assess genetic diversity in C. falcatum. Molecular characterization of the C. falcatum isolates prevalent in north‐eastern India would enable red rot management strate‐gies, selection for resistance genes and development of resistant cultivars.     

Strong Association between Serological Status and Probability of Progression to Clinical Visceral Leishmaniasis in Prospective Cohort Studies in India and Nepal

Introduction

Asymptomatic persons infected with the parasites causing visceral leishmaniasis (VL) usually outnumber clinically apparent cases by a ratio of 4–10 to 1. We assessed the risk of progression from infection to disease as a function of DAT and rK39 serological titers.

Methods

We used available data on four cohorts from villages in India and Nepal that are highly endemic for Leishmania donovani. In each cohort two serosurveys had been conducted. Based on results of initial surveys, subjects were classified as seronegative, moderately seropositive or strongly seropositive using both DAT and rK39. Based on the combination of first and second survey results we identified seroconvertors for both markers. Seroconvertors were subdivided in high and low titer convertors. Subjects were followed up for at least one year following the second survey. Incident VL cases were recorded and verified.

Results

We assessed a total of 32,529 enrolled subjects, for a total follow-up time of 72,169 person years. Altogether 235 incident VL cases were documented. The probability of progression to disease was strongly associated with initial serostatus and with seroconversion; this was particularly the case for those with high titers and most prominently among seroconvertors. For high titer DAT convertors the hazard ratio reached as high as 97.4 when compared to non-convertors. The strengths of the associations varied between cohorts and between markers but similar trends were observed between the four cohorts and the two markers.

Discussion

There is a strongly increased risk of progressing to disease among DAT and/or rK39 seropositives with high titers. The options for prophylactic treatment for this group merit further investigation, as it could be of clinical benefit if it prevents progression to disease. Prophylactic treatment might also have a public health benefit if it can be corroborated that these asymptomatically infected individuals are infectious for sand flies.     

Molecular phylogenetics unveils the ancient evolutionary origins of the enigmatic fairy armadillos

Fairy armadillos or pichiciegos (Xenarthra, Dasypodidae) are among the most elusive mammals. Due to their subterranean and nocturnal lifestyle, their basic biology and evolutionary history remain virtually unknown. Two distinct species with allopatric distributions are recognized: Chlamyphorus truncatus is restricted to central Argentina, while Calyptophractus retusus occurs in the Gran Chaco of Argentina, Paraguay, and Bolivia. To test their monophyly and resolve their phylogenetic affinities within armadillos, we obtained sequence data from modern and museum specimens for two mitochondrial genes (12S RNA [MT-RNR1] and NADH dehydrogenase 1 [MT-ND1]) and two nuclear exons (breast cancer 1 early onset exon 11 [BRCA1] and von Willebrand factor exon 28 [VWF]). Phylogenetic analyses provided a reference phylogeny and timescale for living xenarthran genera. Our results reveal monophyletic pichiciegos as members of a major armadillo subfamily (Chlamyphorinae). Their strictly fossorial lifestyle probably evolved as a response to the Oligocene aridification that occurred in South America after their divergence from Tolypeutinae around 32 million years ago (Mya). The ancient divergence date (～17Mya) for separation between the two species supports their taxonomic classification into distinct genera. The synchronicity with Middle Miocene marine incursions along the Paraná river basin suggests a vicariant origin for pichiciegos by the disruption of their ancestral range. Their phylogenetic distinctiveness and rarity in the wild argue in favor of high conservation priority.     

Telomeric injury by KML001 in human T cells induces mitochondrial dysfunction through the p53-PGC-1α pathway

Telomere erosion and mitochondrial dysfunction are prominent features of aging cells with progressive declines of cellular functions. Whether telomere injury induces mitochondrial dysfunction in human T lymphocytes, the major component of adaptive host immunity against infection and malignancy, remains unclear. We have recently shown that disruption of telomere integrity by KML001, a telomere-targeting drug, induces T cell senescence and apoptosis via the telomeric DNA damage response (DDR). In this study, we used KML001 to further investigate the role and mechanism of telomere injury in mitochondrial dysregulation in aging T cells. We demonstrate that targeting telomeres by KML001 induces mitochondrial dysfunction, as evidenced by increased mitochondrial swelling and decreased mitochondrial membrane potential, oxidative phosphorylation, mitochondrial DNA content, mitochondrial respiration, oxygen consumption, glycolysis, and ATP energy production. Mechanistically, we found that the KML001-induced telomeric DDR activated p53 signaling, which in turn repressed the expression of peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) and nuclear respiratory factor 1 (NRF-1), leading to T cell mitochondrial dysfunction. These results, forging a direct link between telomeric and mitochondrial biology, shed new light on the human T cell aging network, and demonstrate that the p53-PGC-1α-NRF-1 axis contributes to mitochondrial dysfunction in the setting of telomeric DDR. This study suggests that targeting this axis may offer an alternative, novel approach to prevent telomere damage-mediated mitochondrial and T cell dysfunctions to combat a wide range of immune aging-associated human diseases.Subject terms: Immunology, Diseases     

Genetic and phytochemical diversity analysis in <Emphasis Type="Italic">Bunium persicum</Emphasis> populations of north-western Himalaya

The present study explores morphological, genetic and phytochemical composition of Bunium persicum populations belonging to high altitudinal areas of Indian Himalayan region. In total, 23 morphological traits (13 quantitative and 10 qualitative traits) and 32 Random Amplified Polymorphic DNA primers were employed to infer the population structure of the species. Of the fourteen populations, five genetically diverse populations were analyzed for phytochemical diversity. Among morphological traits, inflorescence, seed and branch traits were most significant in detecting variation. At molecular level, primers TIBMBA-06 and OPR-16 were found most polymorphic with respect to Polymorphism Information Content and Marker Index values. Dendrogram grouped all populations into two major clusters while population from Shong region out grouped separately showing its distantness from all other populations. STRUCTURE analysis was done by using Bayesian model, which characterised all populations into four clusters and some degree of admixture was also observed within individuals. Shong population showed distinct genetic makeup as also suggested by dendrogram. Phytochemical analysis showed the presence of 55 components, of which, 2-methyl-3-phenyl propanal, benzeneacetic acid, 1-phellandrene, γ-terpene, α-terpinolene, Δ0.3-carene and sabinene were major components in its essential oils. The present study revealed high genetic and phytochemical diversity in B. persicum accessions from north-western Himalayan regions. Specifically, accessions from Saptal regions were having higher quantity of essential oils and can be selected for cultivation to meet the commercial demand to some extent. Further, the diversity information provided herein can be useful in management and improvement of this species through future breeding programmes.     

Interaction of quantitative trait loci for resistance to common bacterial blight and pathogen isolates in <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.

Common bacterial blight (CBB) is a major disease of common bean (Phaseolus vulgaris L.) worldwide. Genetic resistance is the most effective and environmentally safe approach for controlling CBB, and identification of resistance quantitative trait loci (QTL) can improve response to selection when breeding for CBB resistance. Interactions of CBB resistance QTL and pathogen isolates with different levels of aggressiveness were studied using an F _4:5 recombinant inbreed line (RIL) population, derived from a cross between the susceptible cultivar “Sanilac” and the resistant breeding line “OAC 09-3.” Disease phenotyping was performed under field and growth room conditions using multiple bacterial isolates with differential levels of aggressiveness. QTL analysis was performed with 237 molecular markers. The effect of pathogen isolate on the average phenotypic value in the RIL population and the interaction of RILs and the pathogen isolates were highly significant. Two QTL underlying CBB resistance were detected on Pv08 and Pv03. A major QTL (R ² _p between 15 and 56%) was identified in a 5-cM (380 kbp) interval in the distal end of the long arm of Pv08. This genomic region was significantly associated with multiple disease evaluation traits in field and growth room assays and against different isolates of the pathogen, which included the previously known CBB marker SU91. A new QTL on Pv03 (Xa3.3^SO), associated with the PvSNP85p745405 allele from the susceptible parent, Sanilac, appeared to be an isolate-specific QTL against the aggressive fuscans isolate ISO118. Interaction between the SU91 and Xa3.3^SO QTL resulted in a significant reduction in mean disease severity for almost all disease evaluation traits after plants were challenged with the isolate ISO118. The 7.92 and 7.79% diseased areas in RILs with both QTL, compared with 14.92 and 13.81% in RILs without either in test1 and in test2 quantified by image analysis, showed a 44 and 47% reduction of percent diseased areas, indicating that the two QTL interact to limit the expansion of CBB symptoms after infection by ISO118. The information obtained in this study indicates that while the broad-spectrum SU91 QTL is useful in breeding programs, isolate-specific QTL, such as Xa3.3^SO, will aid in breeding bean varieties with enhanced resistance against aggressive regional isolates.     

Leaf respiration is differentially affected by leaf vs. stand-level night-time warming

Plant respiration is an important physiological process in the global carbon cycle serving as a major carbon flux from the biosphere to the atmosphere. Respiration is sensitive to temperature providing a link between environmental variability, climate change and the global carbon cycle. We measured leaf respiration in Populus deltoides after manipulating the air temperature surrounding part of a single leaf, and compared this to the temperature response of the same leaves after manipulating the temperature of the stand. The short‐term temperature response of respiration (Q₁₀– change in the respiration rate with a 10 °C increase in leaf temperature) was 1.7 when the leaf temperature was manipulated, but 2.1 when the stand‐level temperature was changed. As a result, total night‐time carbon release during the five‐day experiment was 21% lower when using the Q₁₀ estimates from the tradition leaf manipulation compared to the stand‐level manipulation. We conclude that the temperature response of leaf respiration is related to whole plant carbon and energy demands, and that appropriate experimental procedures are required in examining respiratory CO₂ release under variable temperature conditions.