The D14-SDEL1-SPX4 cascade integrates the strigolactone and phosphate signalling networks in rice.

Modern agriculture needs large quantities of phosphate (Pi) fertilisers to obtain high yields. Information on how plants sense and adapt to Pi is required to enhance phosphorus-use efficiency (PUE) and thereby promote agricultural sustainability. Here, we show that strigolactones (SLs) regulate rice root developmental and metabolic adaptations to low Pi, by promoting efficient Pi uptake and translocation from roots to shoots. Low Pi stress triggers the synthesis of SLs, which dissociate the Pi central signalling module of SPX domain-containing protein (SPX4) and PHOSPHATE STARVATION RESPONSE protein (PHR2), leading to the release of PHR2 into the nucleus and activating the expression of Pi-starvation-induced genes including Pi transporters. The SL synthetic analogue GR24 enhances the interaction between the SL receptor DWARF 14 (D14) and a RING-finger ubiquitin E3 ligase (SDEL1). The sdel mutants have a reduced response to Pi starvation relative to wild-type plants, leading to insensitive root adaptation to Pi. Also, SLs induce the degradation of SPX4 via forming the D14-SDEL1-SPX4 complex. Our findings reveal a novel mechanism underlying crosstalk between the SL and Pi signalling networks in response to Pi fluctuations, which will enable breeding of high-PUE crop plants.

Strigolactone and gibberellin signaling coordinately regulate metabolic adaptations to changes in nitrogen availability in rice.

Modern semi-dwarf rice varieties of the "Green Revolution" require a high supply of nitrogen (N) fertilizer to produce high yields. A better understanding of the interplay between N metabolism and plant developmental processes is required for improved N-use efficiency and agricultural sustainability. Here, we show that strigolactones (SLs) modulate root metabolic and developmental adaptations to low N availability for ensuring efficient uptake and translocation of available N. The key repressor DWARF 53 (D53) of the SL signaling pathway interacts with the transcription factor GROWTH-REGULATING FACTOR 4 (GRF4) and prevents GRF4 from binding to its target gene promoters. N limitation induces the accumulation of SLs, which in turn promotes SL-mediated degradation of D53, leading to the release of GRF4 and thus promoting the expression of genes associated with N metabolism. N limitation also induces degradation of the DELLA protein SLENDER RICE 1 (SLR1) in an D14- and D53-dependent manner, effectively releasing GRF4 from competitive inhibition caused by SLR1. Collectively, our findings reveal a previously unrecognized mechanism underlying SL and gibberellin crosstalk in response to N availability, advancing our understanding of plant growth-metabolic coordination and facilitating the design of the strategies for improving N-use efficiency in high-yield crops.

Correction: PRH1 mediates ARF7-LBD dependent auxin signaling to regulate lateral root development in Arabidopsis thaliana.

[This corrects the article DOI: 10.1371/journal.pgen.1008044.].

Higher nitrogen content and auxin export from rice tiller enhance low-ammonium-dependent tiller outgrowth.

In the early growth stage, nutrient uptake by rice roots is weak. However, rice tillering at this stage would require high N input. Thus, it is vital to clarify the mechanism involved in tillering capacity with low N inputs. In this report, two widely-planted japonica cultivars (cvs Yangyujing 2 and Nanjing 45) were selected mainly because, unlike cv. Nanjing 45, cv. Yangyujing 2 shows low-N-induced tiller outgrowth. Responses of tillers in two rice cultivars to mixture of N forms versus sole NH4+ supply were similar, suggesting that NH4+ plays a pivotal role in N-modulated rice tillering. Under low NH4+ supply, higher expression of OsAMT1.2, OsAMT1.3, OsGS1;2, and OsGS2 was recorded in the roots of cv. Yangyujing 2 in comparison with cv. Nanjing 45, ultimately resulting in higher N content and dry weight in cv. Yangyujing 2. Stronger 3H-IAA export from tiller stems was observed in cv. Yangyujing 2, mainly due to higher expression level of auxin efflux transporters. Moreover, tillers in auxin efflux transporter mutant ospin9 did not respond to NH4+ supply relative to wild-type plants. These findings can be used in the molecular breeding of rice varieties to simultaneously improve rice population productivity and reduce N fertilizer input.

Increased glutamine synthetase by overexpression of TaGS1 improves grain yield and nitrogen use efficiency in rice.

Improving nitrogen use efficiency (NUE) has been a focal point for crop growth and yield throughout the world. Glutamine synthetase (GS), which plays a fundamental role in N metabolism, has been exploited to improve crop NUE. However, increased GS activity in rice by overexpressing its own GS genes hasn't shown superior plant productivity. Here, transgenic rice plants with increased GS activity by overexpressing TaGS1 were analyzed under field and culture conditions at two N rates. Transgenic expression of TaGS1 significantly increases GS activity in leaves, junctions and roots of rice plants relative to wide-type plants. When rice plants grown under consecutive field trials with N rates of 60 and 240 kg/ha, three transgenic lines have higher grain yield than wild-type plants, with increment of 15%-22% in T2 generation and with that of 28%-36% in T3 generation, respectively. And increased panicle numbers (effective tiller numbers) mainly contribute to the advantage of grain yield in transgenic plants. Analysis of N use-related traits shows that transgenic plants with enhanced GS activity promote root capacity to obtain N, N accumulation during growth stages and N remobilization to grains, ultimately conferring 31%-40% improvement of NUE relative to wild-type rice plants.

The role of auxin in nitrogen-modulated shoot branching.

Shoot branching is determined by axillary bud formation and outgrowth and remains one of the most variable determinants of yield in many crops. Plant nitrogen (N) acquired mainly in the forms of nitrate and ammonium from soil, dominates plant development, and high-yield crop production relies heavily on N fertilization. In this review, the regulation of axillary bud outgrowth by N availability and forms is summarized in plant species. The mechanisms of auxin function in this process have been well characterized and reviewed, while recent literature has highlighted that auxin export from a bud plays a critical role in N-modulating this process.

PRH1 mediates ARF7-LBD dependent auxin signaling to regulate lateral root development in Arabidopsis thaliana.

The development of lateral roots in Arabidopsis thaliana is strongly dependent on signaling directed by the AUXIN RESPONSE FACTOR7 (ARF7), which in turn activates LATERAL ORGAN BOUNDARIES DOMAIN (LBD) transcription factors (LBD16, LBD18 and LBD29). Here, the product of PRH1, a PR-1 homolog annotated previously as encoding a pathogen-responsive protein, was identified as a target of ARF7-mediated auxin signaling and also as participating in the development of lateral roots. PRH1 was shown to be strongly induced by auxin treatment, and plants lacking a functional copy of PRH1 formed fewer lateral roots. The transcription of PRH1 was controlled by the binding of both ARF7 and LBDs to its promoter region.

[A report of first fatal case of H10N8 avian influenza virus pneumonia in the world].

OBJECTIVE: To report the treatment process of the first case of human pneumonia resulted from H10N8 avian influenza virus infection in the world for providing the data for clinical diagnosis and treatment. METHODS: On November 30, 2013, the first case of human infection with H10N8 avian influenza virus was discovered in Nanchang City, Jiangxi Province. Its clinical symptoms and epidemiology were analyzed and compared with the characteristics of human infection with H7N9 avian influenza virus. RESULTS: A 73-year old female patient complaining of cough and chest tightness for 3 days and fever for 1 day was admitted to the Department of Respiratory Diseases of the Third Affiliated Hospital of Nanchang University on November 30, 2013. As the illness became worse, the patient was transferred into Intensive Care Unit (ICU) of the Department of Critical Care Medicine on December 2. The patient's condition deteriorated, manifesting multiple organ failure (MOF) on December 5. At 08:30 on December 6, cardiac arrest occurred, and the patient died after inefficient resuscitation. (1) Epidemiological investigation: the patient was an elderly woman, suffering from a variety of chronic diseases (hypertension, coronary heart disease, myasthenia gravis, etc) and impaired immune function (undergone thymectomy), all of them were predisposing factors for deterioration of her health. She had visited the live poultry market one week before admission, and developed symptoms of influenza. The transmission route was the respiratory tract, which was similar to H7N9 avian influenza. (2) CLINICAL MANIFESTATIONS: the patient had flu-like symptoms, such as cough and fever (39.1 centigrade), but no headache or myalgia. Two days later pneumonia accompanied with respiratory distress developed and a large amount of bloody sputum was sucked out through tracheostomy tube (2 000 mL/24 h). Acute kidney injury, acute respiratory distress syndrome (ARDS), septic shock, and unconsciousness occurred, all of which was consistent with the diagnosis of H7N9 avian influenza. (3) Auxiliary examination: with the exception of a decrease in lymphocyte ratio (0.070), aspartate aminotransferase (AST) was slightly increased (57 U/L), C- reactive protein (CRP) was elevated (>200 mg/L), but the platelet count, creatine kinase, lactate dehydrogenase, alanine aminotransferase and myoglobin were not increased, while leucocyte count was increased slightly (10.34×10(9)/L). The changes in above indexes did not match the characteristics of H7N9 avian influenza. However, the aggravated consolidation of the lung conformed to that of H7N9 avian influenza. (4) DIAGNOSIS AND TREATMENT: according to the clinical manifestations, aggravation of consolidation of the lung, and epidemiological evidence, the diagnosis of avian influenza was considered. Though therapeutic dose of oseltamivir was given as antiviral treatment for the early therapy, and other therapeutic measures such as energetic respiratory and circulatory support, and immunosuppressant therapy were given, the patient eventually died from respiratory failure and shock. (5) The Chinese disease prevention and control center (CDC) confirmed that, the patient was infected H10N8 avian influenza virus. No person with close contact with the patient was infected, as screened by Nanchang City and Chinese CDC. CONCLUSIONS: Human infection with H10N8 avian influenza was not exactly the same as that of H7N9. It was difficult to get true information from the conventional laboratory examinations, while the clinical characteristic and epidemiology were essential for the diagnosis. Referring to the treatment regime for human infection with H7N9 avian influenza virus, therapeutic dose of neuraminidase inhibitors could not reverse deterioration of pulmonary pathology. Chinese CDC found that the risk of human infection and transmission of H10N8 avian influenza virus through personal contact was low.