The EDS1-PAD4-ADR1 node mediates Arabidopsis pattern-triggered immunity.

Plants deploy cell-surface and intracellular leucine rich-repeat domain (LRR) immune receptors to detect pathogens1. LRR receptor kinases and LRR receptor proteins at the plasma membrane recognize microorganism-derived molecules to elicit pattern-triggered immunity (PTI), whereas nucleotide-binding LRR proteins detect microbial effectors inside cells to confer effector-triggered immunity (ETI). Although PTI and ETI are initiated in different host cell compartments, they rely on the transcriptional activation of similar sets of genes2, suggesting pathway convergence upstream of nuclear events. Here we report that PTI triggered by the Arabidopsis LRR receptor protein RLP23 requires signalling-competent dimers of the lipase-like proteins EDS1 and PAD4, and of ADR1 family helper nucleotide-binding LRRs, which are all components of ETI. The cell-surface LRR receptor kinase SOBIR1 links RLP23 with EDS1, PAD4 and ADR1 proteins, suggesting the formation of supramolecular complexes containing PTI receptors and transducers at the inner side of the plasma membrane. We detected similar evolutionary patterns in LRR receptor protein and nucleotide-binding LRR genes across Arabidopsis accessions; overall higher levels of variation in LRR receptor proteins than in LRR receptor kinases are consistent with distinct roles of these two receptor families in plant immunity. We propose that the EDS1-PAD4-ADR1 node is a convergence point for defence signalling cascades, activated by both surface-resident and intracellular LRR receptors, in conferring pathogen immunity.

Genetics of autoimmunity in plants: an evolutionary genetics perspective.

Autoimmunity in plants has been found in numerous hybrids as a form of hybrid necrosis and mutant panels. Uncontrolled cell death is a main cellular outcome of autoimmunity, which negatively impacts growth. Its occurrence highlights the vulnerable nature of the plant immune system. Genetic investigation of autoimmunity in hybrid plants revealed that extreme variation in the immune receptor repertoire is a major contributor, reflecting an evolutionary conundrum that plants face in nature. In this review, we discuss natural variation in the plant immune system and its contribution to fitness. The value of autoimmunity genetics lies in its ability to identify combinations of a natural immune receptor and its partner that are predisposed to triggering autoimmunity. The network of immune components for autoimmunity becomes instrumental in revealing mechanistic details of how immune receptors recognize cellular invasion and activate signaling. The list of autoimmunity-risk variants also allows us to infer evolutionary processes contributing to their maintenance in the natural population. Our approach to autoimmunity, which integrates mechanistic understanding and evolutionary genetics, has the potential to serve as a prognosis tool to optimize immunity in crops.

The BIR2/BIR3-Associated Phospholipase Dγ1 Negatively Regulates Plant Immunity.

Plants have evolved effective strategies to defend themselves against pathogen invasion. Starting from the plasma membrane with the recognition of microbe-associated molecular patterns (MAMPs) via pattern recognition receptors, internal cellular signaling pathways are induced to ultimately fend off the attack. Phospholipase D (PLD) hydrolyzes membrane phospholipids to produce phosphatidic acid (PA), which has been proposed to play a second messenger role in immunity. The Arabidopsis (Arabidopsis thaliana) PLD family consists of 12 members, and for some of these, a specific function in resistance toward a subset of pathogens has been shown. We demonstrate here that Arabidopsis PLDγ1, but not its close homologs PLDγ2 and PLDγ3, is specifically involved in plant immunity. Genetic inactivation of PLDγ1 resulted in increased resistance toward the virulent bacterium Pseudomonas syringae pv. tomato DC3000 and the necrotrophic fungus Botrytis cinerea As pldγ1 mutant plants responded with elevated levels of reactive oxygen species to MAMP treatment, a negative regulatory function for this PLD isoform is proposed. Importantly, PA levels in pldγ1 mutants were not affected compared to stressed wild-type plants, suggesting that alterations in PA levels are not likely the cause for the enhanced immunity in the pldγ1 line. Instead, the plasma-membrane-attached PLDγ1 protein colocalized and associated with the BAK1-INTERACTING RECEPTOR-LIKE KINASES BIR2 and BIR3, which are known negative regulators of pattern-triggered immunity. Moreover, complex formation of PLDγ1 and BIR2 was further promoted upon MAMP treatment. Hence, we propose that PLDγ1 acts as a negative regulator of plant immune responses in complex with immunity-related proteins BIR2 and BIR3.

Photosynthesis-inspired H2 generation using a chlorophyll-loaded liposomal nanoplatform to detect and scavenge excess ROS.

A disturbance of reactive oxygen species (ROS) homeostasis may cause the pathogenesis of many diseases. Inspired by natural photosynthesis, this work proposes a photo-driven H2-evolving liposomal nanoplatform (Lip NP) that comprises an upconversion nanoparticle (UCNP) that is conjugated with gold nanoparticles (AuNPs) via a ROS-responsive linker, which is encapsulated inside the liposomal system in which the lipid bilayer embeds chlorophyll a (Chla). The UCNP functions as a transducer, converting NIR light into upconversion luminescence for simultaneous imaging and therapy in situ. Functioning as light-harvesting antennas, AuNPs are used to detect the local concentration of ROS for FRET biosensing, while the Chla activates the photosynthesis of H2 gas to scavenge local excess ROS. The results thus obtained indicate the potential of using the Lip NPs in the analysis of biological tissues, restoring their ROS homeostasis, possibly preventing the initiation and progression of diseases.

Plant cell surface immune receptor complex signaling.

Plant plasma membrane pattern recognition receptors are key to microbe sensing and activation of immunity to microbial invasion. Plants employ several types of such receptors that differ mainly in the structure of their ectodomains and the presence or absence of a cytoplasmic protein kinase domain. Plant immune receptors do not function as single entities, but form larger complexes which undergo compositional changes in a ligand-dependent manner. Here, we highlight current knowledge of molecular mechanisms underlying receptor complex dynamics and regulation, and cover early signaling networks implicated in the activation of generic plant immune responses. We further discuss how an increasingly comprehensive set of immune receptors may be employed to engineer crop plants with enhanced, durable resistance to microbial infection.

Comparing Arabidopsis receptor kinase and receptor protein-mediated immune signaling reveals BIK1-dependent differences.

Pattern recognition receptors (PRRs) sense microbial patterns and activate innate immunity against attempted microbial invasions. The leucine-rich repeat receptor kinases (LRR-RK) FLS2 and EFR, and the LRR receptor protein (LRR-RP) receptors RLP23 and RLP42, respectively, represent prototypical members of these two prominent and closely related PRR families. We conducted a survey of Arabidopsis thaliana immune signaling mediated by these receptors to address the question of commonalities and differences between LRR-RK and LRR-RP signaling. Quantitative differences in timing and amplitude were observed for several early immune responses, with RP-mediated responses typically being slower and more prolonged than those mediated by RKs. Activation of RLP23, but not FLS2, induced the production of camalexin. Transcriptomic analysis revealed that RLP23-regulated genes represent only a fraction of those genes differentially expressed upon FLS2 activation. Several positive and negative regulators of FLS2-signaling play similar roles in RLP23 signaling. Intriguingly, the cytoplasmic receptor kinase BIK1, a positive regulator of RK signaling, acts as a negative regulator of RP-type immune receptors in a manner dependent on BIK1 kinase activity. Our study unveiled unexpected differences in two closely related receptor systems and reports a new negative role of BIK1 in plant immunity.

An In†Situ Depot for Continuous Evolution of Gaseous H2 Mediated by a Magnesium Passivation/Activation Cycle for Treating Osteoarthritis.

Inflammation is involved in many human pathologies, including osteoarthritis (OA). Hydrogen (H2 ) is known to have anti-inflammatory effects; however, the bioavailability of directly administered H2 gas is typically poor. Herein, a local delivery system that can provide a high therapeutic concentration of gaseous H2 at inflamed tissues is proposed. The delivery system comprises poly(lactic-co-glycolic acid) microparticles that contain magnesium powder (Mg@PLGA MPs). Mg@PLGA MPs that are intra-muscularly injected close to the OA knee in a mouse model can act as an in situ depot that can evolve gaseous H2 continuously, mediated by the cycle of passivation/activation of Mg in body fluids, at a concentration that exceeds its therapeutic threshold. The analytical data that are obtained in the biochemical and histological studies indicate that the proposed Mg@PLGA MPs can effectively mitigate tissue inflammation and prevent cartilage from destruction, arresting the progression of OA changes.

In Situ Nanoreactor for Photosynthesizing H2 Gas To Mitigate Oxidative Stress in Tissue Inflammation.

Hydrogen gas can reduce cytotoxic reactive oxygen species (ROS) that are produced in inflamed tissues. Inspired by natural photosynthesis, this work proposes a multicomponent nanoreactor (NR) that comprises chlorophyll a, l-ascorbic acid, and gold nanoparticles that are encapsulated in a liposomal (Lip) system that can produce H2 gas in situ upon photon absorption to mitigate inflammatory responses. Unlike a bulk system that contains free reacting molecules, this Lip NR system provides an optimal reaction environment, facilitating rapid activation of the photosynthesis of H2 gas, locally providing a high therapeutic concentration thereof. The photodriven NR system reduces the degrees of overproduction of ROS and pro-inflammatory cytokines both in vitro in RAW264.7 cells and in vivo in mice with paw inflammation that is induced by lipopolysaccharide (LPS). Histological examinations of tissue sections confirm the ability of the NR system to reduce LPS-induced inflammation. Experimental results indicate that the Lip NR system that can photosynthesize H2 gas has great potential for mitigating oxidative stress in tissue inflammation.

In situ depot comprising phase-change materials that can sustainably release a gasotransmitter H2S to treat diabetic wounds.

Patients with diabetes mellitus are prone to develop refractory wounds. They exhibit reduced synthesis and levels of circulating hydrogen sulfide (H2S), which is an ephemeral gaseous molecule. Physiologically, H2S is an endogenous gasotransmitter with multiple biological functions. An emulsion method is utilized to prepare a microparticle system that comprises phase-change materials with a nearly constant temperature of phase transitions to encapsulate sodium hydrosulfide (NaHS), a highly water-labile H2S donor. An emulsion technique that can minimize the loss of water-labile active compounds during emulsification must be developed. The as-prepared microparticles (NaHS@MPs) provide an in situ depot for the sustained release of exogenous H2S under physiological conditions. The sustained release of H2S promotes several cell behaviors, including epidermal/endothelial cell proliferation and migration, as well as angiogenesis, by extending the activation of cellular ERK1/2 and p38, accelerating the healing of full-thickness wounds in diabetic mice. These experimental results reveal the strong potential of NaHS@MPs for the sustained release of H2S for the treatment of diabetic wounds.

Recent advances in CO2 bubble-generating carrier systems for localized controlled release.

This article reviews recent progress in the development of carbon dioxide (CO2) bubble-generating drug carriers, including their designs and operating mechanisms; these carriers constitute an advanced class of stimuli-responsive delivery systems with considerable potential. The drug carriers contain stimuli-responsive agents, which are stable before they reach the target location, but enable rapid drug release that is triggered by the generation of CO2 bubbles, which are chemically inert, under certain stimuli. These CO2 bubble-generating carrier systems can be used to accumulate locally a delivered drug at the diseased tissue, while reducing side effects on the normal tissue, improving their therapeutic effectiveness. Since the generated CO2 bubbles are hyperechogenic, they may also be used as an ultrasound contrast agent in elucidating the status of the carriers and providing real-time diagnostic images. Perspectives of the future of applications of gases with therapeutic effects, such as nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), in such bubble-generating carrier systems, are also briefly discussed.

Acidity-triggered charge-convertible nanoparticles that can cause bacterium-specific aggregation in situ to enhance photothermal ablation of focal infection.

Focal infections that are caused by antibiotic-resistant bacteria are becoming an ever-growing challenge to human health. To address this challenge, a pH-responsive amphiphilic polymer of polyaniline-conjugated glycol chitosan (PANI-GCS) that can self-assemble into nanoparticles (NPs) in situ is developed. The PANI-GCS NPs undergo a unique surface charge conversion that is induced by their local pH, favoring bacterium-specific aggregation without direct contact with host cells. Following conjugation onto GCS, the optical-absorbance peak of PANI is red-shifted toward the near-infrared (NIR) region, enabling PANI-GCS NPs to generate a substantial amount of heat, which is emitted to their neighborhood. The local temperature of the NIR-irradiated PANI-GCS NPs is estimated to be approximately 5 °C higher than their ambient tissue temperature, ensuring specific and direct heating of their aggregated bacteria; hence, damage to tissue is reduced and wound healing is accelerated. The above results demonstrate that PANI-GCS NPs are practical for use in the photothermal ablation of focal infections.

Signal transduction and regulation of IbpreproHypSys in sweet potato.

Hydroxyproline-rich glycopeptides (HypSys) are small signalling peptides containing 18-20 amino acids. The expression of IbpreproHypSys, encoding the precursor of IbHypSys, was induced in sweet potato (Ipomoea batatas cv. Tainung 57) through wounding and IbHypSys treatments by using jasmonate and H2 O2 . Transgenic sweet potatoes overexpressing (OE) and silencing [RNA interference (RNAi)] IbpreproHypSys were created. The expression of the wound-inducible gene for ipomoelin (IPO) in the local and systemic leaves of OE plants was stronger than the expression in wild-type (WT) and RNAi plants after wounding. Furthermore, grafting experiments indicated that IPO expression was considerably higher in WT stocks receiving wounding signals from OE than from RNAi scions. However, wounding WT scions highly induced IPO expression in OE stocks. These results indicated that IbpreproHypSys expression contributed towards sending and receiving the systemic signals that induced IPO expression. Analysing the genes involved in the phenylpropanoid pathway demonstrated that lignin biosynthesis was activated after synthetic IbHypSys treatment. IbpreproHypSys expression in sweet potato suppressed Spodoptera litura growth. In conclusion, wounding induced the expression of IbpreproHypSys, whose protein product was processed into IbHypSys. IbHypSys stimulated IbpreproHypSys and IPO expression and enhanced lignin biosynthesis, thus protecting plants from insects.

Controlled Release of an Anti-inflammatory Drug Using an Ultrasensitive ROS-Responsive Gas-Generating Carrier for Localized Inflammation Inhibition.

Inflammation is associated with many diseases, in which activated inflammatory cells produce various reactive oxygen species (ROS), including H2O2. This work proposes an ultrasensitive ROS-responsive hollow microsphere (HM) carrier that contains an anti-inflammatory drug, an acid precursor consisting of ethanol and FeCl2, and sodium bicarbonate (SBC) as a bubble-generating agent. In cases of inflamed osteoarthritis, the H2O2 at low concentration diffuses through the HMs to oxidize their encapsulated ethanol in the presence of Fe(2+) by the Fenton reaction, establishing an acidic milieu. In acid, SBC decomposes to form CO2 bubbles, disrupting the shell wall of the HMs and releasing the anti-inflammatory drug to the problematic site, eventually protecting against joint destruction. These results reveal that the proposed HMs may uniquely exploit biologically relevant concentrations of H2O2 and thus be used for the site-specific delivery of therapeutics in inflamed tissues.

[Clinical review of enteral feeding of extremely low birth weight infants].

OBJECTIVE: To review the clinical data of enteral feeding of extremely low birth weight infants (ELBWI), and analyze the influencing factors. METHOD: From Jan. 2000 to Jan. 2010, data of 31 ELBWI from Peking Union Medical College Hospital were retrospectively collected. ELBWI were assigned to different groups according to the time achieving full enteral feeding, comparison was done between two groups for enteral feeding. RESULT: Twenty-four infants were analyzed, their mean gestational age was (29.0 ± 1.8) weeks (26.14 - 34.43 weeks), birth weight (882 ± 67) g (730 - 970 g), there were 11 infants in group A, whose time for achieving full enteral feeding was (27 ± 6)days, there were 13 infants in group B, whose time achieving full enteral feeding was (46 ± 10)days. The ratio of asphyxia (18.2% vs. 61.5%, P = 0.047), duration of umbilical vein catheterization longer than 10 days (18.2% vs. 61.5%, P = 0.047), and duration of mechanical ventilation longer than 14 days (27.3% vs. 76.9%, P = 0.038) in group A was higher than in group B. The milk volume on the 21st and 28th day in group A was much more than that in group B [(88.9 ± 35.4) ml vs. (37.4 ± 34.9) ml, P = 0.002; (121.1 ± 37.4) ml vs. (53.2 ± 33.1) ml, P = 0.000]. There were no significant differences between the two groups in gestational age, birth weight, patent ductus arterious, erythrocytosis, dysglycemia, sepsis, the time to begin enteral feeding, the beginning milk volume, the adding milk volume in the 1st, 2nd week, and the milk volume on the 3rd, 7th, 14th day. CONCLUSION: Asphyxia, duration of umbilical vein catheterization, and duration of mechanical ventilation are likely to influence the enteral feeding of ELBWI, ELBWI with successful enteral feeding could show good tolerance in the 3rd week. But individual program should be made for enteral feeding of ELBWI, because enteral feeding could be influenced by multiple factors.