Okayama Prefectural Kurashiki Chuo High School

Chloroplasts are a sensitive target of arsenic (As) toxicity. How chloroplasts are protected against As toxicity remains unclear. We isolated an As-hypersensitive Arabidopsis thaliana mutant, aic2 cad1-3, from an ethyl methanesulfonate-mutagenized cad1-3 background defective in phytochelatin synthase. This double mutant displayed enhanced leaf chlorosis, reduced chloroplast number, impaired chloroplast structure, and larger growth inhibition under As stress compared with cad1-3. Map-based cloning identified the causal gene for the mutant phenotype as DJA4 belonging to the J-protein family. DJA4 protein was localized to the chloroplast stroma. The aic2 single mutant and DJA4 knockout mutants were also more sensitive to As than wild-type. Microscale thermophoresis analysis showed that the recombinant DJA462-403 protein binds arsenite. Genetic analyses demonstrated that double knockout of DJA4 and TOC132 (Translocon at the Outer envelope membrane of Chloroplasts) resulted in greater As sensitivity compared with single-gene knockouts. Chloroplast proteomic analysis identified nine proteins commonly altered in both dja4 and toc132 mutants under As stress, many of which are involved in chloroplast metabolism and redox homeostasis. These results show that DJA4 plays a crucial role in maintaining chloroplast function under As stress by binding with arsenite and protecting the chloroplast protein import machinery.

During the symbiosis of legumes with nitrogen-fixing bacteria, collectively called rhizobia, suppression of excessive rhizobial infection by host plants is important to maximize the benefits of symbiotic nitrogen fixation. However, the molecular mechanism involved in the suppression remains relatively poorly understood. We performed LC-MS and RNA-Seq analysis using rhizobia-infected Lotus japonicus roots and investigated the role of phosphatidylinositol (PI) and phosphatidylinositol phosphates (PIPs) in the symbiosis. Phosphatidylinositol transfer protein (PITP)-like proteins 4 (PLP4), phosphatidylinositol 3-phosphate 5-kinase 4 (PIP5K4), and PIP5K6 mutants, which are involved in the vesicular transport of lipids and phosphorylation of PIPs, were used to show the involvement of the signaling of PI and PIPs. Accumulation of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] during rhizobial infection was examined by a fluorescent marker 1×TUBBY-C (TUBBY). We found that PI signaling-related genes were upregulated, and the amount of PIP2 increased in L. japonicus roots during rhizobial infection. In the PLP4, PIP5K4, and PIP5K6 mutants, rhizobial infection increased, while PIP2 accumulation failed. Furthermore, the observation of PI(4,5)P2 in rhizobia-infected roots revealed that ectopic accumulation was closely related to the suppression of rhizobial infection. Our findings indicate that the accumulation of PI(4,5)P2, mediated by PLP and PIP5Ks, suppresses excessive rhizobial infection in the root epidermis and cortex, leading to the optimal number of nodules.

New Phytologist 224 (2019), 875–885, doi: 10.1111/nph.15813. Since its publication, the authors of Iida et al. (2019) have highlighted an error in their article. In Fig. 5(b), the scale of values provided on the y-axis was incorrect. The corrected Fig. 5 is shown below. We apologize to our readers for this mistake. Corrected Fig. 5:

Spinareoviridae is a large family of icosahedral viruses that are usually regarded as non-enveloped with segmented (9–12 linear segments) dsRNA genomes of 23–29 kbp. Spinareovirids have a broad host range, infecting animals, fungi and plants. Some have important pathogenic potential for humans (e.g. Colorado tick fever virus), livestock (e.g. avian orthoreoviruses), fish (e.g. aquareoviruses) and plants (e.g. rice ragged stunt virus and rice black streaked dwarf virus). This is a summary of the ICTV Report on the family Spinareoviridae, which is available at ictv.global/report/spinareoviridae.

SUMMARYRhizoctonia solani is a soil‐borne necrotrophic fungus that causes sheath blight in grasses. The basal resistance of compatible interactions between R. solani and rice is known to be modulated by some WRKY transcription factors (TFs). However, genes and defense responses involved in incompatible interaction with R. solani remain unexplored, because no such interactions are known in any host plants. Recently, we demonstrated that Bd3‐1, an accession of the model grass Brachypodium distachyon, is resistant to R. solani and, upon inoculation with the fungus, undergoes rapid induction of genes responsive to the phytohormone salicylic acid (SA) that encode the WRKY TFs BdWRKY38 and BdWRKY44. Here, we show that endogenous SA and these WRKY TFs positively regulate this accession‐specific R. solani resistance. In contrast to a susceptible accession (Bd21), the infection process in the resistant accessions Bd3‐1 and Tek‐3 was suppressed at early stages before the development of fungal biomass and infection machinery. A comparative transcriptome analysis during pathogen infection revealed that putative WRKY‐dependent defense genes were induced faster in the resistant accessions than in Bd21. A gene regulatory network (GRN) analysis based on the transcriptome dataset demonstrated that BdWRKY38 was a GRN hub connected to many target genes specifically in resistant accessions, whereas BdWRKY44 was shared in the GRNs of all three accessions. Moreover, overexpression of BdWRKY38 increased R. solani resistance in Bd21. Our findings demonstrate that these resistant accessions can activate an incompatible host response to R. solani, and BdWRKY38 regulates this response by mediating SA signaling.

The relationship between chorioamnionitis (CAM) and neonatal mortality has been extensively investigated, but that of maternal pre-eclampsia and neonatal mortality is unclear. We investigated neonatal mortality and morbidity of maternal pre-eclampsia and clinical CAM in extremely premature infants using data from a population-based cohort study. We retrospectively analyzed data obtained from the Neonatal Research Network in Japan, a population-based cohort study (n = 18900) conducted to clarify the clinical characteristics and morbidity of very low-birthweight infants. Patients were divided into four diagnosis-based groups for comparative analysis: sole pre-eclampsia; sole clinical CAM; concurrent pre-eclampsia and clinical CAM; and non-diagnosis (of pre-eclampsia and clinical CAM). Mortality was higher in the pre-eclampsia groups compared with the groups without (18.3%, 84/459 vs 14.0%, 567/4059; OR, 1.38; 95%CI: 1.07-1.78). In contrast, mortality was not affected by presence of clinical CAM (with, 13.7% 182/1328 vs without, 15.0% 469/3190; OR, 0.92; 95%CI: 0.77-1.11). With regard to small for gestational age, the mortality rate increased by two-three-fold as gestational week decreased. The complication survival rate in the whole group was 35% (1135/3218). Maternal pre-eclampsia is associated with poor prognosis in extremely premature infants. We also need to deliberate on the trade-off between the advantages of early rescue from pre-eclampsia and risk of prematurity.

Multidrug and toxic compound extrusion (MATE) proteins are widely present in bacteria, fungi, plants and mammals. Recent studies have showed that a group of plant MATE genes encodes citrate transporter, which are involved in the detoxification of aluminium or translocation of iron from the roots to the shoots. In this study, we isolated two homologous genes (ScFRDL1 and ScFRDL2) from this family in rye (Secale cereale L.). ScFRDL1 shared 94.2% identity with HvAACT1, an Al-activated citrate transporter in barley (Hordeum vulgare L.) and ScFRDL2 shared 80.6% identity with OsFRDL2, a putative Al-responsive protein in rice (Oryza sativa L.). Both genes were mainly expressed in the roots, however, they showed different expression patterns. Expression of ScFRDL1 was unaffected by Al treatment, but up-regulated by Fe-deficiency treatment. In contrast, expression of ScFRDL2 was greatly induced by Al but not by Fe deficiency. The Al-induced up-regulation of ScFRDL2 was found in both the root tips and basal roots. Furthermore, the expression pattern of ScFRDL2 was consistent with citrate secretion pattern. Immunostaining showed that ScFRDL1 was localised at all cells in the root tips and central cylinder and endodermis in the basal root. Taken together, our results suggest that ScFRDL1 was involved in efflux of citrate into the xylem for Fe translocation from the roots to the shoots, while ScFRDL2 was involved in Al-activated citrate secretion in rye.

A thermostable manganese(II)-dependent 2,3-dihydroxybiphenyl-1,2-dioxygenase derived from Bacillus sp. JF8 was crystallized. The initial screening for crystallization was performed by the sitting-drop vapour-diffusion method using a crystallization robot, resulting in the growth of two crystal forms. The first crystal belonged to space group P1, with unit-cell parameters a = 62.7, b = 71.4, c = 93.6 A, alpha = 71.2, beta = 81.0, gamma = 64.0 degrees, and diffracted to 1.3 A resolution. The second crystal belonged to space group I222, with unit-cell parameters a = 74.2, b = 90.8, c = 104.3 A, and diffracted to 1.3 A resolution. Molecular-replacement trials using homoprotocatechuate 2,3-dioxygenase from Arthrobacter globiformis (28% amino-acid sequence identity) as a search model provided a satisfactory solution for both crystal forms.

A gene encoding heat shock transcription factor (HSF) was cloned and sequenced from cultured cells of the cabbage armyworm, Mamestra brassicae. The cDNA potentially encoded a 699-aa protein, with a calculated molecular weight of 77.8 kDa. Deduced amino acid identities to HSFs from Aedes aegypti and Drosophila melanogaster were 36 and 34%, respectively. Analysis of the genomic DNA revealed eight exons and three optional exons: a, b, and c. Exon a contained a premature in-frame stop codon that would generate a truncated protein. When the cells were exposed to high temperature or cadmium, no particular alternative transcripts showed significant up- or down-regulated expression relative to the total amount of the transcripts. These results suggest that alternative splicing may not be a principal mechanism for regulation of M. brassicae HSF gene expression in response to heat shock and cadmium.

Using common beans differing greatly in the response to photoperiod and low-phosphorus (P) stress, we investigated their responses to acidity and aluminum (Al) toxicity and the relationship between Al tolerance and organic acid exudation under Al or low P stress. A genotype Ginshi was found to be sensitive to low pH treatment. When exposed to pH 4.5, serious curvature in the root tips of cv. Ginshi was observed; however, it was completely corrected by the application of 5 or 10 μmol/L AlCl3; increasing calcium (Ca) could ameliorate Al toxicity, but it could not correct root curvature at pH 4.5. Common beans showed significant differences in both root growth and Al tolerance, and the varieties from the Andes were more tolerant to Al toxicity than those from the Mesoamerican origin. In the presence of 50 μmol/L AlCl3, all the common bean genotypes exuded citrate, and a significant difference in the amounts of citrate was observed among genotypes. The genotypes originated in the Mesoamerica tended to release more citrate than other origins in the presence of Al. The P-inefficient genotype DOR364 exuded more citrate than the P-efficient genotype G19833 in the presence of 50 μmol/L AlCl3, whereas no organic acids were detected in root exudates under low-P stress. A reduction of citrate exudation in the DOR364, but a slight increase of citrate exudation in the G19833, was observed under Al stress after they were exposed to 6-d P starvation. These results suggest that different low-P or Al tolerance in common beans might not be associated with organic acid exudation.