Nitrogen (N) is often a limiting nutrient whose availability determines plant growth and productivity. Because its availability is often low and/or not uniform over time and space in nature, plants respond to variations in N availability by altering uptake and recycling mechanisms, but the molecular mechanisms underlying how these responses are regulated are poorly understood. Here, we show that a group of GARP G2-like transcription factors, NITRATE-INDUCIBLE, GARP-TYPE TRANSCRIPTIONAL REPRESSOR1/HYPERSENSITIVE TO LOW Pi-ELICITED PRIMARY ROOT SHORTENING1 proteins (NIGT1/HRS1s), are factors that bind to the promoter of the N starvation marker and repress an array of N starvation-responsive genes under conditions of high N availability. Transient assays and expression analysis demonstrated that NIGT1/HRS1s are transcriptional repressors whose expression is regulated by N availability. We identified target genes of the NIGT1/HRS1s by genome-wide transcriptome analyses and found that they are significantly enriched in N starvation response-related genes, including N acquisition, recycling, remobilization, and signaling genes. Loss of resulted in deregulation of N acquisition and accumulation. We propose that NIGT1/HRS1s are major regulators of N starvation responses that play an important role in optimizing N acquisition and utilization under fluctuating N conditions.

Plants use nitrate, ammonium, and organic nitrogen in the soil as nitrogen sources. Since the elevated CO2 environment predicted for the near future will reduce nitrate utilization by C3 species, ammonium is attracting great interest. However, abundant ammonium nutrition impairs growth, i.e., ammonium toxicity, the primary cause of which remains to be determined. Here, we show that ammonium assimilation by GLUTAMINE SYNTHETASE 2 (GLN2) localized in the plastid rather than ammonium accumulation is a primary cause for toxicity, which challenges the textbook knowledge. With exposure to toxic levels of ammonium, the shoot GLN2 reaction produced an abundance of protons within cells, thereby elevating shoot acidity and stimulating expression of acidic stress-responsive genes. Application of an alkaline ammonia solution to the ammonium medium efficiently alleviated the ammonium toxicity with a concomitant reduction in shoot acidity. Consequently, we conclude that a primary cause of ammonium toxicity is acidic stress.

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A total of 100 children under the age of 17 years with acquired aplastic anaemia (AA) were initially treated with immunosuppressive therapy (IST) (n = 63) or bone marrow transplantation (BMT) (n = 37) from an HLA-matched family donor. The projected 10-year survival rates were 55 +/- 8% and 97 +/- 3% respectively (P = 0.004). Because the IST group included 11 non-responders who were salvaged by BMT from an HLA-matched unrelated donor, we compared failure-free survival (FFS) between the groups. The probability of FFS at 10 years was 97 +/- 3% for the BMT group, compared with 40 +/- 8% for the IST group (P = 0.0001). Seven patients evolved to myelodysplastic syndrome (MDS) with monosomy 7 and the estimated cumulative incidence of MDS 10 years after diagnosis was 20 +/- 7% in the IST group. We compared the outcome of children treated with IST during the two consecutive periods of 1983-91 (group A, n = 40) and 1991-8 (group B, n = 23) to assess the impact of combined therapy with antithymocyte globulin and cyclosporin. The probability of FFS at 7 years follow-up was the same in the two groups (50 +/- 8% vs. 40 +/- 15%, P = 0.40). We recommend BMT as first-line therapy in paediatric severe AA patients with an HLA-matched family donor. Alternative donor BMT is recommended as salvage therapy in patients who relapse or do not respond to initial IST.

Summary.A total of 100 children under the age of 17 years with acquired aplastic anaemia (AA) were initially treated with immunosuppressive therapy (IST) (n 63) or bone marrow transplantation (BMT) (n 37) from an HLAmatched family donor. The projected 10-year survival rates were 55^8% and 97^3% respectively (P 0´004). Because the IST group included 11 non-responders who were salvaged by BMT from an HLA-matched unrelated donor, we compared failure-free survival (FFS) between the groups. The probability of FFS at 10 years was 97^3% for the BMT group, compared with 40^8% for the IST group (P 0´0001). Seven patients evolved to myelodysplastic syndrome (MDS) with monosomy 7 and the estimated cumulative incidence of MDS 10 years after diagnosis was 20^7% in the IST group. We compared the outcome of children treated with IST during the two consecutive periods of 1983±91 (group A, n 40) and 1991±8 (group B, n 23) to assess the impact of combined therapy with antithymocyte globulin and cyclosporin. The probability of FFS at 7 years follow-up was the same in the two groups (50^8% vs. 40^15%, P 0´40). We recommend BMT as first-line therapy in paediatric severe AA patients with an HLA-matched family donor. Alternative donor BMT is recommended as salvage therapy in patients who relapse or do not respond to initial IST.

Summary. We report a favourable outcome in 15 patients with severe aplastic anaemia (SAA) who were , 20 years of age and who underwent bone marrow transplantation (BMT) from a human leucocyte antigen (HLA)-matched unrelated donor. All patients were non-responders to intensive immunosuppressive therapy (IST) and were multiply transfused. The conditioning regimen consisted of cyclophosphamide (60 mg/kg/d, on d 24 and 23), antithymocyte globulin (2´5 mg/kg/d, on d 25 to 22) and total body irradiation (2´5 Gy  2/d, on d 22 and 21). Patients received cyclosporine and methotrexate for prophylaxis of graft-versus-host disease (GVHD), except for the last four who received tacrolimus instead of cyclosporine. Donor/ recipient pairs were identical for HLA class I and II antigens by serological typing, but four pairs were found to have a mismatch at the HLA-A, -B or -DRB1 locus by highresolution typing. All patients achieved rapid engraftment and are alive at 2±86 months after transplantation (median follow-up, 51 months). Moderate to severe acute GVHD occurred in 5 out of 15 patients (33%); only one patient developed extensive chronic GVHD. Considering our encouraging results, unrelated donor transplantation for SAA is recommended as a salvage therapy in nonresponders to IST.

Isoflavonoids are commonly found in leguminous plants. Glycitein is one of the isoflavones produced by soybean. The genes encoding the enzymes in isoflavone biosynthetic pathway have mostly been identified and characterized. However, the gene(s) for isoflavone O-methyltransferase (IOMT), which catalyses the last step of glycitein biosynthesis, has not yet been identified. In this study, we conducted multi-omics analyses of fungal-inoculated soybean and indicated that glycitein biosynthesis was induced in response to biotic stress. Moreover, we identified a unique type of IOMT which participates in glycitein biosynthesis. Soybean seedlings were inoculated with Aspergillus oryzae or Rhizopus oligosporus and sampled daily for 8 days. Multi-omics analyses were conducted using liquid chromatography-tandem mass spectrometry and RNA sequencing. Metabolome analysis revealed that glycitein derivatives increased following fungal inoculation. Transcriptome co-expression analysis identified two candidate IOMTs that were co-expressed with the gene encoding flavonoid 6-hydroxylase (F6H), the key enzyme in glycitein biosynthesis. The enzymatic assay of the two IOMTs using respective recombinant proteins showed that one IOMT, named as GmIOMT1, produced glycitein. Unlike other IOMTs, GmIOMT1 belongs to the cation-dependent OMT family and exhibited the highest activity with Zn2+ among cations tested. Moreover, we demonstrated that GmIOMT1 overexpression increased the levels of glycitein derivatives in soybean hairy roots when F6H was co-expressed. These results strongly suggest that GmIOMT1 participates in inducing glycitein biosynthesis in response to biotic stress.

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