Insect gallers and their plant hosts : From omics data to systems biology

Gall-inducing insects are capable of exerting a high level of control over their hosts’ cellular machinery to the extent that the plant’s development,metabolism,chemistry,and physiology are all altered in favour of the insect. Many gallers are devastating pests in global agriculture and the limited understanding of their relationship with their hosts prevents the development of robust management strategies. Omics technologies are proving to be important tools in elucidating the mechanisms involved in the interaction as they facilitate analysis of plant hosts and insect effectors for which little or no prior knowledge exists. In this review,we examine the mechanisms behind insect gall development using evidence from omics-level approaches. The secretion of effector proteins and induced phytohormonal imbalances are highlighted as likely mechanisms involved in gall development. However,understanding how these components function within the system is far from complete and a number of questions need to be answered before this information can be used in the development of strategies to engineer or breed plants with enhanced resistance

The Road to Resistance in Forest Trees

In recent years, forests have been exposed to an unprecedented rise in pests and pathogens. This, coupled with the added challenge of climate change, renders forest plantation stock vulnerable to attack and severely limits productivity. Genotypes resistant to such biotic challenges are desired in plantation forestry to reduce losses. Conventional breeding has been a main avenue to obtain resistant genotypes. More recently, genetic engineering has become a viable approach to develop resistance against pests and pathogens in forest trees. Tree genomic resources have contributed to advancements in both these approaches. Genome-wide association studies and genomic selection in tree populations have accelerated breeding tools while integration of various levels of omics information facilitates the selection of candidate genes for genetic engineering. Furthermore, tree associations with non-pathogenic endophytic and subterranean microbes play a critical role in plant health and may be engineered in forest trees to improve resistance in the future. We look at recent studies in forest trees describing defense mechanisms using such approaches and propose the way forward to developing superior genotypes with enhanced resistance against biotic stress

The status of the world's land and marine mammals: diversity, threat, and knowledge

Knowledge of mammalian diversity is still surprisingly disparate, both regionally and taxonomically. Here, we present a comprehensive assessment of the conservation status and distribution of the world's mammals. Data, compiled by 1700+ experts, cover all 5487 species, including marine mammals. Global macroecological patterns are very different for land and marine species but suggest common mechanisms driving diversity and endemism across systems. Compared with land species, threat levels are higher among marine mammals, driven by different processes (accidental mortality and pollution, rather than habitat loss), and are spatially distinct (peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also disproportionately poorly known. These data are made freely available to support further scientific developments and conservation action

The Transcriptome and Terpene Profile of Eucalyptus grandis Reveals Mechanisms of Defense Against the Insect Pest, Leptocybe invasa

Plants have evolved complex defenses that allow them to protect themselves against pests and pathogens. However, there is relatively little information regarding the Eucalyptus defensome. Leptocybe invasa is one of the most damaging pests in global Eucalyptus forestry, and essentially nothing is known regarding the molecular mechanisms governing the interaction between the pest and host. The aim of the study was to investigate changes in the transcriptional landscape and terpene profile of a resistant and susceptible Eucalyptus genotype in an effort to improve our understanding of this interaction. We used RNA-seqencing to investigate tran-scriptional changes following L. invasa oviposition. Expression levels were validated using real-time quantitative PCR. Terpene profiles were investigated using gas chroma-tography coupled to mass spectometry on uninfested and oviposited leaves. We found 698 and 1,115 significantly differentially expressed genes from the resistant and susceptible interactions, respectively. Gene Ontology enrichment and Mapman analyses identified putative defense mechanisms including cell wall reinforcement, protease inhibitors, cell cycle suppression and regulatory hormone signaling pathways. There were significant differences in the mono- and sesquiterpene profiles between genotypes and between control and infested material. A model of the interaction between Eucalyptus and L. invasa was proposed from the transcriptomic and chemical data

Transcriptome Analysis of Eucalyptus grandis Implicates Brassinosteroid Signaling in Defense Against Myrtle Rust (Austropuccinia psidii)

Eucalyptus grandis, in its native Australian range, varies in resistance to Austropuccinia psidii (syn. Puccinia psidii). The biotrophic rust fungus, A. psidii is the causal agent of myrtle rust and poses a serious threat to Australian biodiversity. The pathogen produces yellow pustules of urediniospores on young leaves and shoots, resulting in shoot tip dieback, stunted growth, and death. Dissecting the underlying mechanisms of resistance against this pathogen will contribute to improved breeding and control strategies to mitigate its devastating effects. The aim of this study was to determine the molecular dialogue between E. grandis and A. psidii, using an RNA-sequencing approach. Resistant and susceptible E. grandis seedlings grown from seed collected across its natural range were inoculated with the pandemic biotype of A. psidii. The leaf tissue was harvested at 12-h post inoculation (hpi), 1-day post inoculation (dpi), 2-dpi and 5-dpi and subjected to RNA-sequencing using Illumina 50 bp PE reads to a depth of 40 million reads per sample. Differential gene expression and gene ontology enrichment indicated that the resistant seedlings showed controlled, coordinated responses with a hypersensitive response, while the susceptible seedlings showed no systemic response against myrtle rust. Brassinosteroid signaling was apparent as an enriched term in the resistant interaction at 2-dpi, suggesting an important role of this phytohormone in defense against the pathogen. Brassinosteroid mediated signaling genes were also among the candidate genes within two major disease resistance loci (Puccinia psidii resistance), Ppr3 and Ppr5. While brassinosteroids have been tagged as positive regulators in other plant disease resistance interactions, this is the first report in the Eucalyptus – Austropuccinia psidii interaction. Furthermore, several putative resistance genes, underlying known resistance loci and implicated in the interaction have been identified and highlighted for future functional studies. This study provided further insights into the molecular interactions between E. grandis and A. psidii, contributing to our understanding of this pathosystem

The status of the world's land and marine mammals: Diversity, threat, and knowledge

Knowledge of mammalian diversity is still surprisingly disparate, both regionally and taxonomically. Here, we present a comprehensive assessment of the conservation status and distribution of the world's mammals. Data, compiled by 1700+ experts, cover all 5487 species, including marine mammals. Global macroecological patterns are very different for land and marine species but suggest common mechanisms driving diversity and endemism across systems. Compared with land species, threat levels are higher among marine mammals, driven by different processes (accidental mortality and pollution, rather than habitat loss), and are spatially distinct (peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also disproportionately poorly known. These data are made freely available to support further scientific developments and conservation action