A rhizosphere fungus enhances Arabidopsis thermotolerance through production of an HSP90 inhibitor

The molecular chaperone HEAT SHOCK PROTEIN90 (HSP90) is essential for the maturation of key regulatory proteins in eukaryotes and for the response to temperature stress. Earlier, we have reported that fungi living in association with plants of the Sonoran desert produce small molecule inhibitors of mammalian HSP90. Here, we address whether elaboration of the HSP90 inhibitor monocillin I (MON) by the rhizosphere fungus Paraphaeosphaeria quadriseptata affects plant HSP90 and plant environmental responsiveness. We demonstrate that MON binds Arabidopsis (Arabidopsis thaliana) HSP90 and can inhibit the function of HSP90 in lysates of wheat (Triticum aestivum) germ. MON treatment of Arabidopsis seedlings induced HSP101 and HSP70, conserved components of the stress response. Application of MON, or growth in the presence of MON, allowed Arabidopsis wild type but not AtHSP101 knockout mutant seedlings to survive otherwise lethal temperature stress. Finally, cocultivation of P. quadriseptata with Arabidopsis enhanced plant heat stress tolerance. These data demonstrate that HSP90-inhibitory compounds produced by fungi can influence plant growth and responses to the environment.     

Influenza Infects Lung Microvascular Endothelium Leading to Microvascular Leak: Role of Apoptosis and Claudin-5

Severe influenza infections are complicated by acute lung injury, a syndrome of pulmonary microvascular leak. The pathogenesis of this complication is unclear. We hypothesized that human influenza could directly infect the lung microvascular endothelium, leading to loss of endothelial barrier function. We infected human lung microvascular endothelium with both clinical and laboratory strains of human influenza. Permeability of endothelial monolayers was assessed by spectrofluorimetry and by measurement of the transendothelial electrical resistance. We determined the molecular mechanisms of flu-induced endothelial permeability and developed a mouse model of severe influenza. We found that both clinical and laboratory strains of human influenza can infect and replicate in human pulmonary microvascular endothelium, leading to a marked increase in permeability. This was caused by apoptosis of the lung endothelium, since inhibition of caspases greatly attenuated influenza-induced endothelial leak. Remarkably, replication-deficient virus also caused a significant degree of endothelial permeability, despite displaying no cytotoxic effects to the endothelium. Instead, replication-deficient virus induced degradation of the tight junction protein claudin-5; the adherens junction protein VE-cadherin and the actin cytoskeleton were unaffected. Over-expression of claudin-5 was sufficient to prevent replication-deficient virus-induced permeability. The barrier-protective agent formoterol was able to markedly attenuate flu-induced leak in association with dose-dependent induction of claudin-5. Finally, mice infected with human influenza developed pulmonary edema that was abrogated by parenteral treatment with formoterol. Thus, we describe two distinct mechanisms by which human influenza can induce pulmonary microvascular leak. Our findings have implications for the pathogenesis and treatment of acute lung injury from severe influenza.     

21α,26-dihydroxy-D:A-friedooleanan-3-one from Salacia reticulata var. Diandra (celastraceae)

Carbon-13 NMR has been used to detect the position of angular methyl oxygenation and determine the structure of 21α,26-dihydroxy-D:A-friedooleanan-3-one, a new trioxygenated friedooleanane from Salacia reticulata var. diandra and the assignment has been confirmed chemically.     

Organisation and expression of a cluster of yolk protein genes in the Australian sheep blowfly, Lucilia cuprina

The Australian sheep blowfly Lucilia cuprina is a major pest for the Australian and New Zealand sheep industries. With the long-term aim of making a strain of L. cuprina suitable for a genetic control program, we previously developed a tetracycline-repressible female lethal genetic system in Drosophila. A key part of this system is a female-specific promoter from a yolk protein (yp) gene controlling expression of the tetracycline-dependent transactivator (tTA). Here we report the sequence of a 14.2 kb genomic clone from L. cuprina that contains a cluster of three complete yp genes and one partial yp gene. The Lcyp genes are specifically expressed in females that have received a protein meal. A bioinformatic analysis of the promoter of one of the yp genes (LcypA) identified several putative binding sites for DSX, a known regulator of yp gene expression in other Diptera. A transgenic strain of L. cuprina was made that contained the LcypA promoter driving the expression of the Escherichia coli lacZ reporter gene. Transgenic females express high levels of β-galactosidase after a protein meal. Thus the LcypA promoter could be used to obtain female-specific expression of tTA in transgenic L. cuprina.     

Arabidopsis PTD Is Required for Type Ⅰ Crossover Formation and Affects Recombination Frequency in Two Different Chromosomal Regions

In eukaryotes,crossovers together with sister chromatid cohesion maintain physical association between homologous chromosomes,ensuring accurate chromosome segregation during meiosis I and resulting in exchange of genetic information between homologues.The Arabidopsis PTD(Parting Dancers)gene affects the level of meiotic crossover formation,but its functional relationships with other core meiotic genes,such as AtSPO11-1,AtRAD51,and AtMSH4,are unclear;whether PTD has other functions in meiosis is also unknown.To further analyze PTD function and to test for epistatic relationships,we compared the meiotic chromosome behaviors of Atspol 1-1 ptd and AtradSl ptd double mutants with the relevant single mutants.The results suggest that PTD functions downstream of AtSPOll-1 and AtRAD51 in the meiotic recombination pathway.Furthermore,we found that meiotic defects in rck ptd and Atmsh4 ptd double mutants showed similar meiotic phenotypes to those of the relevant single mutants,providing genetic evidences for roles of PTD and RCK in the type I crossovers pathway.Moreover,we employed a pollen tetrad-based fluorescence method and found that the meiotic crossover frequencies in two genetic intervals were significantly reduced from 6.63%and 22.26%in wild-type to 1.14%and 6.36%,respectively,in the ptd-2 mutant.These results revealed new aspects of PTD function in meiotic crossover formation.     

Arabidopsis PTD Is Required for Type I Crossover Formation and Affects Recombination Frequency in Two Different Chromosomal Regions

In eukaryotes, crossovers together with sister chromatid cohesion maintain physical association between homologous chromosomes, ensuring accurate chromosome segregation during meiosis I and resulting in exchange of genetic information between homologues. The Arabidopsis PTD （Parting Dancers） gene affects the level of meiotic crossover formation, but its functional relationships with other core meiotic genes, such as AtSP011-1, AtRAD51, and AtMSH4, are unclear; whether PTD has other functions in meiosis is also unknown. To further analyze PTD function and to test for epistatic relationships, we compared the meiotic chromosome behaviors ofAtspoll-1 ptd and Atrad51 ptd double mutants with the relevant single mutants. The results suggest that PTD functions downstream of AtSP011-1 and AtRAD51 in the meiotic recombination pathway. Furthermore, we found that meiotic defects in rck pM and Atmsh4 ptd double mutants showed similar meiotic phenotypes to those of the relevant single mutants, providing genetic evidences for roles of PTD and RCK in the type I crossovers pathway. Moreover, we employed a pollen tetrad-based fluorescence method and found that the meiotic crossover frequencies in two genetic intervals were significantly reduced from 6.63% and 22.26% in wild-type to 1.14% and 6.36%, respectively, in the ptd~2 mutant. These results revealed new aspects of PTD function in meiotic crossover formation.     

Novel quantitative trait loci for partial resistance to Phytophthora sojae in soybean PI 398841

Phytophthora root and stem rot caused by Phytophthora sojae Kaufmann and Gerdemann is one of the most severe soybean [Glycine max (L.) Merr] diseases in the USA. Partial resistance is as effective in managing this disease as single-gene (Rps gene)-mediated resistance and is more durable. The objective of this study was to identify quantitative trait loci (QTL) associated with partial resistance to P. sojae in PI 398841, which originated from South Korea. A population of 305 F_7:8 recombinant inbred lines derived from a cross of OX20-8 × PI 398841 was used to evaluate partial resistance against P. sojae isolate C2S1 using a tray test. Composite interval mapping using a genome-wide logarithm of odd (LOD) threshold detected three QTL on chromosomes 1, 13, and 18, which individually explained 4–16 % of the phenotypic variance. Seven additional QTL, accounting for 2–3 % of phenotypic variance each, were identified using chromosome-wide LOD thresholds. Seven of the ten QTL for resistance to P. sojae were contributed by PI 398841. Seven QTL co-localized with known Rps genes and previously reported QTL for soil-borne root pathogens, isoflavone, and seed oil. Three QTL on chromosomes 3, 13, and 18 co-localized with known Rps genes, but PI 398841 did not exhibit an Rps gene-mediated resistance response following inoculation with 48 different isolates of P. sojae. PI 398841 is potentially a source of novel genes for improving soybean cultivars for partial resistance to P. sojae.     

Spatial distribution and association of banana (Musa spp.) Fusarium wilt (Fusarium oxysporum f.sp. cubense) epidemics with biophysical factors in southwestern Ethiopia

Abstract

Field surveys were conducted in 2014 and 2015 to determine the distribution and association of wilt incidence with biophysical factors. Spatio-temporal analysis of wilt epidemics in the farms revealed a wide distribution of the disease. Cropping year, district, cultivar, crop density, planting date, weeding, sucker and bud management, source of moisture and planting materials, presence/absence of wilt in neighboring farms, disease management practices, farmers awareness towards wilt diseases, planting date and cropping system were significantly associated with disease incidence in a multiple-variable model. A wilt incidence of ≤30% had high probability of association to good weed, sucker and male bud management practices, high level of farmers awareness towards wilt, low population density, disease-free suckers, rainfed production, absence of wilt in neighboring farms and good disease management schemes. Findings of this study showed Fusarium wilt is a major constraint and need for on-farm trainings to concerned bodies about wilt management schemes.