In Vivo Detection of Residues Required for Ligand-Selective Activation of the S-Locus Receptor in Arabidopsis

SummaryThe self-incompatibility response of crucifers is a barrier to fertilization in which arrest of pollen tube development is mediated by allele-specific interactions between polymorphic receptors and ligands encoded by the S-locus haplotype. Activation of stigma-expressed S-locus receptor kinase (SRK) [1] by pollen coat-localized S-locus cysteine-rich (SCR) ligand [2–5] and the resulting rejection of pollen occurs only if receptor and ligand are encoded by the same S haplotype [4, 6–8]. To identify residues within the SRK extracellular domain (eSRK) that are required for its ligand-selective activation, we assayed chimeric receptors and receptor variants containing substitutions at polymorphic sites in Arabidopsis thaliana [9, 10]. We show that only a small number of the ∼100 polymorphic residues in eSRK are required for ligand-specific activation of self-incompatibility in vivo. These essential residues occur in two noncontiguous clusters located at equivalent positions in the two variants tested. They also correspond to sites showing elevated levels of substitutions in other SRKs, suggesting that these residues could define self-incompatibility specificity in most SRKs. The results demonstrate that the majority of eSRK residues that show signals of positive selection and previously surmised to function as specificity determinants are not essential for specificity in the SRK-SCR interaction

Unprecedented reorganization of holocentric chromosomes provides insights into the enigma of lepidopteran chromosome evolution

Chromosome evolution presents an enigma in the mega-diverse Lepidoptera. Most species exhibit constrained chromosome evolution with nearly identical haploid chromosome counts and chromosome-level gene collinearity among species more than 140 million years divergent. However, a few species possess radically inflated chromosomal counts due to extensive fission and fusion events. To address this enigma of constraint in the face of an exceptional ability to change, we investigated an unprecedented reorganization of the standard lepidopteran chromosome structure in the green-veined white butterfly (Pieris napi). We find that gene content in P. napi has been extensively rearranged in large collinear blocks, which until now have been masked by a haploid chromosome number close to the lepidopteran average. We observe that ancient chromosome ends have been maintained and collinear blocks are enriched for functionally related genes suggesting both a mechanism and a possible role for selection in determining the boundaries of these genome-wide rearrangements.Peer reviewe

Independent S-Locus Mutations Caused Self-Fertility in Arabidopsis thaliana

A common yet poorly understood evolutionary transition among flowering plants is a switch from outbreeding to an inbreeding mode of mating. The model plant Arabidopsis thaliana evolved to an inbreeding state through the loss of self-incompatibility, a pollen-rejection system in which pollen recognition by the stigma is determined by tightly linked and co-evolving alleles of the S-locus receptor kinase (SRK) and its S-locus cysteine-rich ligand (SCR). Transformation of A. thaliana, with a functional AlSRKb-SCRb gene pair from its outcrossing relative A. lyrata, demonstrated that A. thaliana accessions harbor different sets of cryptic self-fertility–promoting mutations, not only in S-locus genes, but also in other loci required for self-incompatibility. However, it is still not known how many times and in what manner the switch to self-fertility occurred in the A. thaliana lineage. Here, we report on our identification of four accessions that are reverted to full self-incompatibility by transformation with AlSRKb-SCRb, bringing to five the number of accessions in which self-fertility is due to, and was likely caused by, S-locus inactivation. Analysis of S-haplotype organization reveals that inter-haplotypic recombination events, rearrangements, and deletions have restructured the S locus and its genes in these accessions. We also perform a Quantitative Trait Loci (QTL) analysis to identify modifier loci associated with self-fertility in the Col-0 reference accession, which cannot be reverted to full self-incompatibility. Our results indicate that the transition to inbreeding occurred by at least two, and possibly more, independent S-locus mutations, and identify a novel unstable modifier locus that contributes to self-fertility in Col-0

Investigating Behaviour and Population Dynamics of Striped Marlin (Kajikia audax) from the Southwest Pacific Ocean with Satellite Tags

Behaviour and distribution of striped marlin within the southwest Pacific Ocean were investigated using electronic tagging data collected from 2005–2008. A continuous-time correlated random-walk Kalman filter was used to integrate double-tagging data exhibiting variable error structures into movement trajectories composed of regular time-steps. This state-space trajectory integration approach improved longitude and latitude error distributions by 38.5 km and 22.2 km respectively. Using these trajectories as inputs, a behavioural classification model was developed to infer when, and where, ‘transiting’ and ‘area-restricted’ (ARB) pseudo-behavioural states occurred. ARB tended to occur at shallower depths (108±49 m) than did transiting behaviours (127±57 m). A 16 day post-release period of diminished ARB activity suggests that patterns of behaviour were affected by the capture and/or tagging events, implying that tagged animals may exhibit atypical behaviour upon release. The striped marlin in this study dove deeper and spent greater time at ≥200 m depth than those in the central and eastern Pacific Ocean. As marlin reached tropical latitudes (20–21°S) they consistently reversed directions, increased swimming speed and shifted to transiting behaviour. Reversals in the tropics also coincided with increases in swimming depth, including increased time ≥250 m. Our research provides enhanced understanding of the behavioural ecology of striped marlin. This has implications for the effectiveness of spatially explicit population models and we demonstrate the need to consider geographic variation when standardizing CPUE by depth, and provide data to inform natural and recreational fishing mortality parameters

Expression of Distinct Self-Incompatibility Specificities in Arabidopsis thaliana

The interplay of balancing selection within a species and rapid gene evolution between species can confound our ability to determine the functional equivalence of interspecific and intergeneric pairs of alleles underlying reproduction. In crucifer plants, mating specificity in the barrier to self-fertilization called self-incompatibility (SI) is controlled by allele-specific interactions between two highly polymorphic and co-evolving proteins, the S-locus receptor kinase (SRK) and its S-locus cysteine rich (SCR) ligand. These proteins have diversified both within and between species such that it is often difficult to determine from sequence information alone if they encode the same or different SI specificity. The self-fertile Arabidopsis thaliana was derived from an obligate outbreeding ancestor by loss of self-incompatibility, often in conjunction with inactivation of SRK or SCR. Nevertheless, some accessions of A. thaliana can express self-incompatibility upon transformation with an SRK–SCR gene pair isolated from its self-incompatible close relative A. lyrata. Here we show that several additional and highly diverged SRK/SCR genes from A. lyrata and another crucifer plant, Capsella grandiflora, confer self-incompatibility in A. thaliana, either as intact genes isolated from genomic libraries or after manipulation to generate chimeric fusions. We describe how the use of this newly developed chimeric protein strategy has allowed us to test the functional equivalence of SRK/SCR gene pairs from different taxa and to assay the functionality of endogenous A. thaliana SRK and SCR sequences

Change in opioid policies in New England emergency departments, 2014 vs 2018.

OBJECTIVE: The U.S. opioid epidemic persists, yet it is unclear if opioid-related emergency department (ED) policies have changed. We investigated: 1) the prevalence of opioid use disorder (OUD) prevention and treatment policies in New England EDs in 2018, and 2) how these policies have changed since 2014. METHODS: Using the National Emergency Department Inventory-USA, we identified and surveyed all New England EDs in 2015 and 2019 about opioid-related policies in 2014 and 2018, respectively. The surveys assessed OUD prevention policies (to use a screening tool, access the Prescription Drug Monitoring Program [PDMP], notify primary care providers, prescribe/dispense naloxone) and treatment policies (to refer to recovery resources, prescribe/dispense buprenorphine). RESULTS: Of 194 EDs open in 2018, 167 (86 %) completed the survey. Of 193 EDs open in 2018 and 2014, 147 (76 %) completed both surveys. In 2018, the most commonly-reported policy was accessing the PDMP (96 %); the least commonly-reported policy was prescribing/dispensing buprenorphine to at risk patients (37 %). EDs varied in prescribing/dispensing naloxone: 35 % of EDs offered naloxone to ≥80 % of patients at risk of opioid overdose versus 33 % of EDs to \u3c10 \u3e% of patients at risk. Most EDs (74 %) reported prescribing/dispensing buprenorphine to \u3c10 \u3e% of patients with OUD. Comparing 2018 to 2014, the greatest difference in policy use was in prescribing/dispensing naloxone (+55 %, p \u3c 0.001). CONCLUSION: Implementation of opioid-related ED policies increased between 2014 and 2018. Continued effort is needed to understand the extent to which policy implementation translates to clinical care, and to best translate evidence-based policies into clinical practice

Screening for Health-Related Social Needs of Emergency Department Patients.

STUDY OBJECTIVE: There has been increasing attention to screening for health-related social needs. However, little is known about the screening practices of emergency departments (EDs). Within New England, we seek to identify the prevalence of ED screening for health-related social needs, understand the factors associated with screening, and understand how screening patterns for health-related social needs differ from those for violence, substance use, and mental health needs. METHODS: We analyzed data from the 2018 National Emergency Department Inventory-New England survey, which was administered to all 194 New England EDs during 2019. We used descriptive statistics to compare ED characteristics by screening practices, and multivariable logistic regression models to identify factors associated with screening. RESULTS: Among the 166 (86%) responding EDs, 64 (39%) reported screening for at least one health-related social need, 160 (96%) for violence (including intimate partner violence or other violent exposures), 148 (89%) for substance use disorder, and 159 (96%) for mental health needs. EDs reported a wide range of social work resources to address identified needs, with 155 (93%) reporting any social worker availability and 41 (27%) reporting continuous availability. CONCLUSION: New England EDs are screening for health-related social needs at a markedly lower rate than for violence, substance use, and mental health needs. EDs have relatively limited resources available to address health-related social needs. We encourage research on the development of scalable solutions for identifying and addressing health-related social needs in the ED