Significance Statement Developmental acclimation to light intensity in plants involves changes in the organisation and regulation of photosynthetic electron transfer chain components in the chloroplast thylakoid membrane. Here, using mass spectrometry, we quantified changes in the thylakoid proteome and correlated these with key photosynthetic parameters to gain insight into the process.

Grana stacking in plant chloroplast thylakoid membranes dynamically responds to the light environment. These dynamics have been linked to regulation of the relative antenna sizes of PSI and PSII (state transitions), the PSII repair cycle, and the regulation of photosynthetic electron transfer. Here, we used 3D structured illumination microscopy, a subdiffraction-resolution fluorescence imaging technique, to investigate the light-intensity dependence, kinetics, reversibility, and regulation of dynamic thylakoid stacking in spinach (Spinacia oleracea) and Arabidopsis (Arabidopsis thaliana). Low-intensity white light (150 mmol photons m 22 s 21) behaved similarly to light preferentially exciting PSII (660 nm), causing a reduction in grana diameter and an increased number of grana per chloroplast. By contrast, high-intensity white light (1000 mmol photons m 22 s 21), darkness, and light preferentially exciting PSI (730 nm) reversed these changes. These dynamics occurred with a half-time of 7 to 8 min and were accompanied by state transitions. Consistent with this, the dynamics were dependent on STN7 (light-harvesting complex II [LHCII] kinase) and TAP38 (LHCII phosphatase), which are required for state transitions but were unaffected by the absence of STN8 (PSII kinase) or PSII core phosphatase (PSII phosphatase). Unlike state transitions, however, thylakoid stacking dynamics did not rely on the presence of the LHCI and PSI subunit L phospho-LHCII binding sites on PSI. Since oligomerization of thylakoid curvature protein (CURT1A) was unaffected by the absence of STN7 or TAP38, we conclude that the primary determinant of dynamic thylakoid stacking is LHCII phosphorylation.

The dissemination of cancer cells to local and distant sites depends on a complex and poorly understood interplay between malignant cells and the cellular and non-cellular components surrounding them, collectively termed the tumour microenvironment. One of the most abundant cell types of the tumour microenvironment is the fibroblast, which becomes corrupted by locally derived cues such as TGF-β1 and acquires an altered, heterogeneous phenotype (cancer-associated fibroblasts, CAF) supportive of tumour cell invasion and metastasis. Efforts to develop new treatments targeting the tumour mesenchyme are hampered by a poor understanding of the mechanisms underlying the development of CAF. Here, we examine the contribution of microRNA to the development of experimentally-derived CAF and correlate this with changes observed in CAF derived from tumours. Exposure of primary normal human fibroblasts to TGF-β1 resulted in the acquisition of a myofibroblastic CAF-like phenotype. This was associated with increased expression of miR-145, a miRNA predicted in silico to target multiple components of the TGF-β signalling pathway. miR-145 was also overexpressed in CAF derived from oral cancers. Overexpression of miR-145 blocked TGF-β1-induced myofibroblastic differentiation and reverted CAF towards a normal fibroblast phenotype. We conclude that miR-145 is a key regulator of the CAF phenotype, acting in a negative feedback loop to dampen acquisition of myofibroblastic traits, a key feature of CAF associated with poor disease outcome.

Compared to controlled laboratory conditions, plant growth in the field is rarely optimal since it is frequently challenged by large fluctuations in light and temperature which lower the efficiency of photosynthesis and lead to photo‐oxidative stress. Plants grown under natural conditions therefore place an increased onus on the regulatory mechanisms that protect and repair the delicate photosynthetic machinery. Yet, the exact changes in thylakoid proteome composition which allow plants to acclimate to the natural environment remain largely unexplored. Here, we use quantitative label‐free proteomics to demonstrate that field‐grown Arabidopsis plants incorporate aspects of both the low and high light acclimation strategies previously observed in laboratory‐grown plants. Field plants showed increases in the relative abundance of ATP synthase, cytochrome b6f, ferredoxin‐NADP+ reductases (FNR1 and FNR2) and their membrane tethers TIC62 and TROL, thylakoid architecture proteins CURT1A, CURT1B, RIQ1, and RIQ2, the minor monomeric antenna complex CP29.3, rapidly‐relaxing non‐photochemical quenching (qE)‐related proteins PSBS and VDE, the photosystem II (PSII) repair machinery and the cyclic electron transfer complexes NDH, PGRL1B, and PGR5, in addition to decreases in the amounts of LHCII trimers composed of LHCB1.1, LHCB1.2, LHCB1.4, and LHCB2 proteins and CP29.2, all features typical of a laboratory high light acclimation response. Conversely, field plants also showed increases in the abundance of light harvesting proteins LHCB1.3 and CP29.1, zeaxanthin epoxidase (ZEP) and the slowly‐relaxing non‐photochemical quenching (qI)‐related protein LCNP, changes previously associated with a laboratory low light acclimation response. Field plants also showed distinct changes to the proteome including the appearance of stress‐related proteins ELIP1 and ELIP2 and changes to proteins that are largely invariant under laboratory conditions such as state transition related proteins STN7 and TAP38. We discuss the significance of these alterations in the thylakoid proteome considering the unique set of challenges faced by plants growing under natural conditions.

Bacterial C-type haem-copper oxidases in the cbb3 family are widespread in microaerophiles, which exploit their high oxygen-binding affinity for growth in microoxic niches. In microaerophilic pathogens, C-type oxidases can be essential for infection, yet little is known about their biogenesis compared to model bacteria. Here, we have identified genes involved in cbb3-oxidase (Cco) assembly and activity in the Gram-negative pathogen Campylobacter jejuni, the commonest cause of human food-borne bacterial gastroenteritis. Several genes of unknown function downstream of the oxidase structural genes ccoNOQP were shown to be essential (cj1483c and cj1486c) or important (cj1484c and cj1485c) for Cco activity; Cj1483 is a CcoH homologue, but Cj1484 (designated CcoZ) has structural similarity to MSMEG_4692, involved in Qcr-oxidase supercomplex formation in Mycobacterium smegmatis. Blue-native polyacrylamide gel electrophoresis of detergent solubilised membranes revealed three major bands, one of which contained CcoZ along with Qcr and oxidase subunits. Deletion of putative copper trafficking genes ccoI (cj1155c) and ccoS (cj1154c) abolished Cco activity, which was partially restored by addition of copper during growth, while inactivation of cj0369c encoding a CcoG homologue led to a partial reduction in Cco activity. Deletion of an operon encoding PCuAC (Cj0909) and Sco (Cj0911) periplasmic copper chaperone homologues reduced Cco activity, which was partially restored in the cj0911 mutant by exogenous copper. Phenotypic analyses of gene deletions in the cj1161c–1166c cluster, encoding several genes involved in intracellular metal homeostasis, showed that inactivation of copA (cj1161c), or copZ (cj1162c) led to both elevated intracellular Cu and reduced Cco activity, effects exacerbated at high external Cu. Our work has therefore identified (i) additional Cco subunits, (ii) a previously uncharacterized set of genes linking copper trafficking and Cco activity, and (iii) connections with Cu homeostasis in this important pathogen.

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Background The primary objective was to identify the frequency of recurrent Streptococcus agalactiae (GBS) bacteremia and associated risk factors for recurrence. The secondary objective was to determine the source of the initial GBS bacteremia and complications. Methods This was a retrospective observational study evaluating patients who were admitted to any of the 12 hospitals within the Northwell Health System from 1/1/2016 to 1/1/2020. Non-pregnant patients ≥ 18 years of age with GBS bacteremia were included. Recurrence was defined as admission due to GBS bacteremia within 1 year after a positive blood culture. Statistical methods performed include t-test or Wilcoxon Rank Sum test, Chi-square, Fisher exact tests, and both univariable and multivariable logistic regressions. Results 390 patients met inclusion criteria with a median age of 63 years old. Majority were white (61.5%) and male (54.1%). Recurrence was found in 18 of 390 patients (4.62%). There was a significant increase in recurrence for patients allergic to penicillin or cephalosporins (p< 0.03), patients with implantable cardiac devices (ICDs) (p< 0.03) and patients who did not receive β-lactams and/or vancomycin as initial treatment (p< 0.05). 6 of the 18 patients were allergic to penicillin or cephalosporins. The estimated odds of recurrence in patients with ICDs were ∼5.4 times the odds of those without ICDs controlling for allergies (p< 0.04, 95% CI 1.7 – 20.0) or controlling for initial antimicrobial treatment (p< 0.04, 95% CI 1.5 – 18.7). The most common sources of GBS bacteremia were skin and soft tissue (35.1%), unknown (27.9%), and urinary tract (6.41%). Endocarditis was diagnosed in 8 patients (2.05%) via transesophageal echocardiogram. Other complications of GBS bacteremia included vertebral osteomyelitis (3.08%), epidural abscess (0.77%), and septic arthritis (0.77%). Median treatment duration was 15 days, with no significant difference in recurrence (p=0.75). Conclusion GBS bacteremia recurred in 4.62% of patients. Recurrence was significantly associated with ICDs, penicillin or cephalosporin allergies, and not receiving β-lactam and/or vancomycin-based regimens as initial therapy. The substantial rate of recurrent GBS bacteremia has important clinical implications. Disclosures All Authors: No reported disclosures.

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