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Background Brassinosteroids (BRs) are a new group of plant hormones and play important roles in plant growth and development. However, little information is available if BRs could regulate spikelet development in rice (Oryza sativa L.) especially under soil-drying conditions. This study investigated whether and how BRs mediate the effect of soil-drying on spikelet differentiation and degeneration in rice. A rice cultivar was field-grown and exposed to three soil moisture treatments during panicle development, that is, well-watered (WW), moderate soil-drying (MD) and severe soil-drying (SD). Results Compared with the WW treatment, the MD treatment enhanced BRs biosynthesis in young panicles, increased spikelet differentiation and reduced spikelet degeneration. The SD treatment had the opposite effects. Changes in expression levels of key rice inflorescence development genes (OsAPO2 and OsTAW1), ascorbic acid (AsA) content, and activities of enzymes involved AsA synthesis and recycle, and amount of nonstructural carbohydrates (NSC) in young panicles were consistent with those in BRs levels, whereas hydrogen peroxide (H2O2) content showed opposite trend. Knockdown of the BRs synthesis gene OsD11 or application of a BRs biosynthesis inhibitor to young panicles markedly decreased OsAPO2 and OsTAW1 expression levels, BRs and AsA contents, activities of enzymes involved AsA synthesis and recycle, NSC amount in rice panicles and spikelet differentiation but increased the H2O2 content and spikelet degeneration compared to the control (the wide type or application of water). The opposite effects were observed when exogenous BRs were applied. Conclusions The results suggest that BRs mediate the effect of soil-drying on spikelet differentiation and degeneration, and elevated BRs levels in rice panicles promote spikelet development under MD by enhancing inflorescence meristem activity, AsA recycle and NSC partitioning to the growing panicles.

Exosome‐derived miRNAs are regarded as biomarkers for the diagnosis and prognosis of many human cancers. However, its function in clear cell renal cell carcinoma (ccRCC) remains unclear. In this study, differentially expressed miRNAs from urinal exosomes were identified using next‐generation sequencing (NGS) and verified using urine samples of ccRCC patients and healthy donors. Then, the exosomes were analysed in early‐stage ccRCC patients, healthy individuals and patients suffering from other urinary system cancers. Thereafter, the target gene of the miRNA was detected. Its biological function was investigated in vitro and in vivo. The results showed that miR‐30c‐5p could be amplified in a stable manner. Its expression pattern was significantly different only between ccRCC patients and healthy control individuals, but not compared with that of other urinary system cancers, which indicated its specificity for ccRCC. Additionally, the overexpression of miR‐30c‐5p inhibited ccRCC progression in vitro and in vivo. Heat‐shock protein 5 (HSPA5) was found to be a direct target gene of miR‐30c‐5p. The depletion of HSPA5 caused by miR‐30c‐5p inhibition reversed the promoting effect of ccRCC growth. In conclusion, urinary exosomal miR‐30c‐5p acts as a potential diagnostic biomarker of early‐stage ccRCC and may be able to modulate the expression of HSPA5, which is correlated with the progression of ccRCC.

The plant steroid hormones brassinosteroids (BRs) play pivotal roles in modulating flower and fruit production. Nitrogen (N) is a key factor affecting rice (Oryza sativa L.) production. We hypothesized that BRs would respond to N application rates at spikelet differentiation (SD) and regulate spikelet degeneration in rice. Three rice cultivars were field‐grown and treated with five N rates at SD. Plant N and BRs contents, antioxidant capacity, and energy status were observed during meiosis in young panicles, and their relationships with spikelet degeneration were evaluated. In all the N treatments, the BRs, adenosine triphosphate, and energy charge levels, activities of the enzymes involved in energy metabolism, including cytochrome C oxidase and succinate dehydrogenase, total antioxidant capacity, and grain yield, were the highest, whereas hydrogen peroxide (H2O2) content and vacuolar processing enzymes (VPE) genes expression levels, and spikelet degeneration rate were the lowest when plant N content was 2.6% during meiosis. The rice BRs‐deficient mutants showed substantial reduction in BRs levels, antioxidant capacity, and energy status, but great increase in H2O2 content, VPE genes expression levels, and spikelet degeneration rate than the wild type (WT); moreover, these parameters in WT panicles could be regulated, whereas in BRs‐deficient mutant panicles, they were not distinctly affected by N application. The results indicated that BRs mediate the effects of N rates on spikelet degeneration, and elevated BRs levels in rice panicles effectively inhibit spikelet degeneration when plant N content is 2.6% during meiosis by elevating antioxidant capacity and energy status.

Background The heterotrimeric G protein β subunit RGB1 plays an important role in plant growth and development. However, the molecular mechanisms underlying the regulation of rice growth by RGB1 remain elusive. Results Here, the rgb1 mutants rgb1–1 (+ 1 bp), rgb1–2 (− 1 bp), and rgb1–3 (− 11 bp) were isolated using the CRISPR/Cas9 system, and they were arrested at 1 day after germination and ultimately exhibited seedling lethality. The dynamic anatomical characteristics of the embryos of the rgb1 seedlings and WT during early postgermination and according to TUNEL assays showed that the suppressed growth of the rgb1 mutants was caused by cell death. In addition to the limited shoot and root development, the development of the embryo shoot-root axis was suppressed in the rgb1 mutants. RGB1 was expressed mainly in the root epidermal and vascular tissues of the embryo. Moreover, transcript profiling analysis revealed that the expression of a large number of auxin-, cytokinin-, and brassinosteroid-inducible genes was upregulated or downregulated in the rgb1 mutant compared to the wild type during seedling development. Conclusions Overall, the rgb1 mutants provide an ideal material for exploring the molecular mechanism underlying rice seedling formation during early postgermination development by G proteins. Significance statement The heterotrimeric G protein β subunit RGB1 acts as a crucial factor in promoting early postgermination seedling development in rice. Electronic supplementary material The online version of this article (10.1186/s12284-019-0313-y) contains supplementary material, which is available to authorized users.

Table S1. Oligonucleotide primers and probe sequences used. (DOC 113 kb)

Figure S5. Comparison of gene expression determined by qRT-PCR and RNA-seq and relative expression of auxin signaling-related genes in the embryos of the WT and rgb1–2 mutants at 2 and 3 days after germination. (a) Comparison of relative gene expression levels determined by RNA-seq and qRT-PCR. Pearson’s test indicated a strong correlation between the two techniques (r = 0.85; p

Figure S3. Induction of RGB1 expression by NAA and measurements of the concentrations of endogenous hormones in the rgb1 mutant and WT. (a) Relative expression of RGB1 in 7-day-old wild-type seedlings grown in mock medium and in medium supplemented with 10 ÎźM NAA. (b-f) Mass spectrometric measurements of different endogenous hormones in the embryos of 3-day-old seedlings. (b) IAA, (c) BRs, (d) IPA, (e) ABA, (f) GA3. (DOCX 2663 kb)

Figure S4. Stages of seed germination and early postgermination seedlings of rice. (DOCX 4775 kb)

Table S3. Number of differentially expressed genes identified in the transcriptome analysis. (DOCX 13 kb)

Figure S2. Phenotypes and genotypes of the rgb1 mutants; relative expression of G protein genes in the embryos of the WT and rgb1 mutants. (a-d) DNA sequences and phenotypes of the WT and rgb1 mutants. (a) WT, (b) rgb1–1, (c) rgb1–2, (d) rgb1–3. Mutations are shown in red. (e) Relative expression of RGB1 in the embryos of the WT and the rgb1–1 and rgb1–2 mutant lines, as determined by qRT-PCR. The forward primer used in the qRT-PCR assays was the RGB1-Cas9 target sequence. (f-h) Relative expression of G protein family genes in the embryos of the WT and the rgb1–1 and rgb1–2 mutant lines from (f) 1-day-old seedlings, (g) 2-day-old seedlings, and (h) 3-day-old seedlings. (DOCX 2619 kb)

Figure S1. Pollen viability and embryo structures in the RGB1/rgb1 heterozygous mutant lines. (a) Pollen viability in the WT and RGB1/rgb1 heterozygous mutants (Bar = 200 μm). The pollen grains were stained with 1% I2–KI and imaged with a Leica DM 1000 light microscope. (b) Median longitudinal sections of WT and RGB1/rgb1 heterozygous mutant seeds (18 days after flowering); a plumule, b radicle. (DOCX 3952 kb)

Additional file 1: Table S1. List of the primers used for qRT-PCR analyses. Fig. S1 Changes in relative expression levels of genes in young panicles of the rice cultivar YD-6 under well-watered, moderate soil-drying and severe soil-drying treatments. Fig. S2 Changes in relative expression levels of genes in young panicles of WT and DR-1 under well-watered and moderate soil-drying treatments. Fig. S3 Changes in relative expression levels of key rice inflorescence development genes in young panicles of YD-6, ZH10 (WT) and OsD11 RNAi line (DR-1) under various soil moisture treatments. Fig. S4 Effect of exogenous brassinosteroids and brassinazole on relative expression levels of ascorbic acid synthesis and cycle, or sugar metabolism genes in young panicles of YD-6, ZH10 (WT) and OsD11 RNAi line (DR-1). Fig. S5 Effect of exogenous brassinosteroids and brassinazole on relative expression levels of key rice inflorescence development genes in young panicles of YD-6, ZH10 (WT) and OsD11 RNAi line (DR-1). Fig. S6 Effect of exogenous brassinosteroids and brassinazole on physiological traits and spikelet development of rice cultivar YD-6 under well-watered and severe soil-drying treatments. Fig. S7 Effect of exogenous H2O2, ascorbic acid and sucrose on endogenous H2O2 content in young panicles, spikelet differentiation and degeneration of YD-6, ZH10 (WT) and OsD11 RNAi line (DR-1).

This study investigated whether and how brassinosteroids (BRs) mediate the effect of soil-drying during meiosis on spikelet degeneration in rice (Oryza sativa L.). A field-grown rice cultivar was exposed to three soil moisture treatments during meiosis: well-watered (WW), moderate soil-drying (MD) and severe soil-drying (SD). Compared with the WW treatment, the MD treatment enhanced BRs biosynthesis, reduced spikelet degeneration, and increased grain yield. The SD treatment had the opposite effects. Changes in the levels of adenosine triphosphate (ATP), energy charge, activities of enzymes involved in energy metabolism, including cytochrome C oxidase (CCO) and succinate dehydrogenase (SDH), and total antioxidant capacity (T-AOC) were consistent with those in BRs levels, whereas the hydrogen peroxide (H2O2) content, vacuolar processing enzyme genes (OsVPE2 and OsVPE3) expression levels and the degree of nuclear DNA fragmentation showed the opposite trend. Knockdown of the BRs synthesis gene OsD11 or application of a BRs biosynthesis inhibitor to young panicles vastly decreased the BRs and ATP contents, energy charge, CCO and SDH activities, and T-AOC in young panicles but increased the H2O2 content, OsVPE2 and OsVPE3 expression, and spikelet degeneration compared to the control, and the opposite effects were observed when exogenous BRs were applied. Therefore, BRs likely mediate the effect of soil-drying on spikelet degeneration, and elevated BRs levels in rice panicles inhibit spikelet degeneration under moderate soil-drying during meiosis by elevating antioxidant capacity and energy status.