Biological nitrogen fixation by two Acacia species and associated root-nodule bacteria in a suburban Australian forest subjected to prescribed burning

Purpose: Prescribed burning is a forest management practice which can lead to nitrogen (N)-limited conditions. This study aimed to explore whether biological N2 fixation (BNF) remained the main source of N acquisition for two understorey Acacia species in a Eucalyptus-dominated suburban forest of subtropical Australia, 3 to 6 years after prescribed burning. Root-nodule bacteria associated with these acacias were also characterised to unravel the differences in rhizobial communities between sites and species. Material and methods: Two sites, burned 3 and 6 years before sample collection, were selected within a dry subtropical forest of south-east Queensland, Australia. Leaves were collected from individuals of Acacia disparrima and A. leiocalyx at each site to determine leaf total carbon (C) and N content, C and N isotope composition (δ13C and δ15N) and the percentage of N derived from atmospheric N2. Nodules were harvested from both acacia species at each site to isolate root nodule bacteria. Bacterial isolates were processed for 16S rDNA gene sequencing. Results and discussion: Generally, no differences were found in plant physiological variables between the two acacia species. Six years after the fire, both species still depended upon BNF for their N supply, with a higher dependence in winter than in summer. Fire, although of low intensity, was likely to have created a N-limited environment which induced the reliance of legumes on BNF. Root nodule bacteria were dominated by non-rhizobial endophytes, mainly from the Firmicutes phylum. No difference in nodule bacterial diversity was found between sites. The relative abundance of rhizobial genera varied amongst plant species and sites, with a shift in dominance from Bradyrhizobium to Rhizobium species between sites 1 and 2. Conclusions: Our results show that even 6 years after burning, ecosystem remained under N stress and BNF was still the main mechanism for N acquisition by the understorey legumes.</p

Biological nitrogen fixation by two Acacia species and associated root-nodule bacteria in a suburban Australian forest subjected to prescribed burning

Purpose: Prescribed burning is a forest management practice which can lead to nitrogen (N)-limited conditions. This study aimed to explore whether biological N fixation (BNF) remained the main source of N acquisition for two understorey Acacia species in a Eucalyptus-dominated suburban forest of subtropical Australia, 3 to 6 years after prescribed burning. Root-nodule bacteria associated with these acacias were also characterised to unravel the differences in rhizobial communities between sites and species. Material and methods: Two sites, burned 3 and 6 years before sample collection, were selected within a dry subtropical forest of south-east Queensland, Australia. Leaves were collected from individuals of Acacia disparrima and A. leiocalyx at each site to determine leaf total carbon (C) and N content, C and N isotope composition (δ C and δ N) and the percentage of N derived from atmospheric N . Nodules were harvested from both acacia species at each site to isolate root nodule bacteria. Bacterial isolates were processed for 16S rDNA gene sequencing. Results and discussion: Generally, no differences were found in plant physiological variables between the two acacia species. Six years after the fire, both species still depended upon BNF for their N supply, with a higher dependence in winter than in summer. Fire, although of low intensity, was likely to have created a N-limited environment which induced the reliance of legumes on BNF. Root nodule bacteria were dominated by non-rhizobial endophytes, mainly from the Firmicutes phylum. No difference in nodule bacterial diversity was found between sites. The relative abundance of rhizobial genera varied amongst plant species and sites, with a shift in dominance from Bradyrhizobium to Rhizobium species between sites 1 and 2. Conclusions: Our results show that even 6 years after burning, ecosystem remained under N stress and BNF was still the main mechanism for N acquisition by the understorey legumes. 2 2 13 1

Antifungal Effect of Copper Nanoparticles against Fusarium kuroshium, an Obligate Symbiont of Euwallacea kuroshio Ambrosia Beetle

Copper nanoparticles (Cu-NPs) have shown great antifungal activity against phytopathogenic fungi, making them a promising and affordable alternative to conventional fungicides. In this study, we evaluated the antifungal activity of Cu-NPs against Fusarium kuroshium, the causal agent of Fusarium dieback, and this might be the first study to do so. The Cu-NPs (at different concentrations) inhibited more than 80% of F. kuroshium growth and were even more efficient than a commercial fungicide used as a positive control (cupric hydroxide). Electron microscopy studies revealed dramatic damage caused by Cu-NPs, mainly in the hyphae surface and in the characteristic form of macroconidia. This damage was visible only 3 days post inoculation with used treatments. At a molecular level, the RNA-seq study suggested that this growth inhibition and colony morphology changes are a result of a reduced ergosterol biosynthesis caused by free cytosolic copper ions. Furthermore, transcriptional responses also revealed that the low- and high-affinity copper transporter modulation and the endosomal sorting complex required for transport (ESCRT) are only a few of the distinct detoxification mechanisms that, in its conjunction, F. kuroshium uses to counteract the toxicity caused by the reduced copper ion

Molecular evidence of the avocado defense response to Fusarium kuroshium infection: a deep transcriptome analysis using RNA-Seq

Fusarium kuroshium is a novel member of the Ambrosia Fusarium Clade (AFC) that has been recognized as one of the symbionts of the invasive Kuroshio shot hole borer, an Asian ambrosia beetle. This complex is considered the causal agent of Fusarium dieback, a disease that has severely threatened natural forests, landscape trees, and avocado orchards in the last 8 years. Despite the interest in this species, the molecular responses of both the host and F. kuroshium during the infection process and disease establishment remain unknown. In this work, we established an in vitro pathosystem using Hass avocado stems inoculated with F. kuroshium to investigate differential gene expression at 1, 4, 7 and 14 days post-inoculation. RNA-seq technology allowed us to obtain data from both the plant and the fungus, and the sequences obtained from both organisms were analyzed independently. The pathosystem established was able to mimic Fusarium dieback symptoms, such as carbohydrate exudation, necrosis, and vascular tissue discoloration. The results provide interesting evidence regarding the genes that may play roles in the avocado defense response to Fusarium dieback disease. The avocado data set comprised a coding sequence collection of 51,379 UniGenes, from which 2,403 (4.67%) were identified as differentially expressed. The global expression analysis showed that F. kuroshium responsive UniGenes can be clustered into six groups according to their expression profiles. The biologically relevant functional categories that were identified included photosynthesis as well as responses to stress, hormones, abscisic acid, and water deprivation. Additionally, processes such as oxidation-reduction, organization and biogenesis of the cell wall and polysaccharide metabolism were detected. Moreover, we identified orthologues of nucleotide-binding leucine-rich receptors, and their possible action mode was analyzed. In F. kuroshium, we identified 57 differentially expressed genes. Interestingly, the alcohol metabolic process biological category had the highest number of upregulated genes, and the enzyme group in this category may play an important role in the mechanisms of secondary metabolite detoxification. Hydrolytic enzymes, such as endoglucanases and a pectate lyase, were also identified, as well as some proteases. In conclusion, our research was conducted mainly to explain how the vascular tissue of a recognized host of the ambrosia complex responds during F. kuroshium infection since Fusarium dieback is an ambrosia beetle-vectored disease and many variables facilitate its establishment

Additional file 5: of Identification of candidate genes related to calanolide biosynthesis by transcriptome sequencing of Calophyllum brasiliense (Calophyllaceae)

Coding sequences alignment between PAL-like C. brasiliense unigenes and Arabidopsis PAL1 protein. (TXT 8 kb

Additional file 11: of Identification of candidate genes related to calanolide biosynthesis by transcriptome sequencing of Calophyllum brasiliense (Calophyllaceae)

Coding sequences alignment between CYP-like unigenes from C. brasiliense and CYP proteins from different plant species involved in furanocoumarins biosynthesis. (TXT 74 kb

Additional file 3: Figures S1-S9. of Identification of candidate genes related to calanolide biosynthesis by transcriptome sequencing of Calophyllum brasiliense (Calophyllaceae)

Figure S1: Gene ontology classification of C. brasiliense unigenes. Figure S2: Biological processes assigned to differentially expressed genes. Figure S3: Re-constructed C. brasiliense metabolic network from glucose to trans-cinnamate. Figure S4: Phylogenetic relationships, primary protein structures and identities percent of trans-cinnamate 4-hydroxylases proteins. Figure S5: Structural and phylogenetic analysis of 4-coumarate: CoA ligases (4CL) from C. brasiliense. Figure S6: Alignment of the 4-coumaroyl 2′-hydroxylases from C. brasiliense. Figure S7: Schematic representation of the Wagner-Meerwein rearrangement. Figure S8: C. brasiliense prenyltransferases. Figure S9: Phylogenetic tree of selected C. brasiliense cytochrome P450. (PPTX 1219 kb

Additional file 6: of Identification of candidate genes related to calanolide biosynthesis by transcriptome sequencing of Calophyllum brasiliense (Calophyllaceae)

Coding sequences alignment between C. brasiliense and Arabidopsis PAL proteins. (TXT 16 kb

Additional file 8: of Identification of candidate genes related to calanolide biosynthesis by transcriptome sequencing of Calophyllum brasiliense (Calophyllaceae)

Coding sequences alignment between C. brasiliense and Arabidopsis 4CL proteins. (TXT 18 kb

Genomic Signals of Adaptation towards Mutualism and Sociality in Two Ambrosia Beetle Complexes

Mutualistic symbiosis and eusociality have developed through gradual evolutionary processes at different times in specific lineages. Like some species of termites and ants, ambrosia beetles have independently evolved a mutualistic nutritional symbiosis with fungi, which has been associated with the evolution of complex social behaviors in some members of this group. We sequenced the transcriptomes of two ambrosia complexes (Euwallacea sp. near fornicatus&ndash;Fusarium euwallaceae and Xyleborus glabratus&ndash;Raffaelea lauricola) to find evolutionary signatures associated with mutualism and behavior evolution. We identified signatures of positive selection in genes related to nutrient homeostasis; regulation of gene expression; development and function of the nervous system, which may be involved in diet specialization; behavioral changes; and social evolution in this lineage. Finally, we found convergent changes in evolutionary rates of proteins across lineages with phylogenetically independent origins of sociality and mutualism, suggesting a constrained evolution of conserved genes in social species, and an evolutionary rate acceleration related to changes in selective pressures in mutualistic lineages