OsPRMT6a-mediated arginine methylation of OsJAZ1 regulates jasmonate signaling and spikelet development in rice.

Although both protein arginine methylation (PRMT) and jasmonate (JA) signaling are crucial for regulating plant development, the relationship between these processes in spikelet development control remains unclear. Here, we utilized CRISPR/Cas9 technology to generate two OsPRMT6a loss-of-function mutants exhibiting various abnormal spikelet structures. Additionally, we found that OsPRMT6a could methylate arginine residues in the JA signal repressors OsJAZ1 and OsJAZ7. Arginine methylation of OsJAZ1 increased the affinity of OsJAZ1 for the JA receptors OsCOI1a and OsCOI1b in the presence of jasmonates (JAs), subsequently promoting the ubiquitination of OsJAZ1 by the SCFOsCOI1a/OsCOI1b complex and degradation via the 26S proteasome. This process ultimately released OsMYC2, a core transcriptional regulator in the JA signaling pathway, to activate or repress JA-responsive genes, thereby maintaining normal plant (spikelet) development. However, in the osprmt6a-1 mutant, reduced arginine methylation of OsJAZ1 impaired the interaction between OsJAZ1 and OsCOI1a/OsCOI1b in the presence of JAs. As a result, OsJAZ1 proteins became more stable, repressing JA responses, thus causing the formation of abnormal spikelet structures. Moreover, we discovered that JA signaling reduced the OsPRMT6a mRNA level in an OsMYC2-dependent manner, thereby establishing a negative feedback loop to balance JA signaling. Furthermore, we found that OsPRMT6a-mediated arginine methylation of OsJAZ1 likely serves as a switch to tune JA signaling to maintain normal spikelet development under harsh environmental conditions such as high temperatures. Thus, our study established a direct molecular link between arginine methylation and the JA signaling pathway.

FLOURY ENDOSPERM24, a heat shock protein 101 (HSP101), is required for starch biosynthesis and endosperm development in rice.

Endosperm is the main storage organ in cereal grain and determines grain yield and quality. The molecular mechanisms of heat shock proteins in regulating starch biosynthesis and endosperm development remain obscure. Here, we report a rice floury endosperm mutant flo24 that develops abnormal starch grains in the central starchy endosperm cells. Map-based cloning and complementation test showed that FLO24 encodes a heat shock protein HSP101, which is localized in plastids. The mutated protein FLO24T296I dramatically lost its ability to hydrolyze ATP and to rescue the thermotolerance defects of the yeast hsp104 mutant. The flo24 mutant develops more severe floury endosperm when grown under high-temperature conditions than normal conditions. And the FLO24 protein was dramatically induced at high temperature. FLO24 physically interacts with several key enzymes required for starch biosynthesis, including AGPL1, AGPL3 and PHO1. Combined biochemical and genetic evidence suggests that FLO24 acts cooperatively with HSP70cp-2 to regulate starch biosynthesis and endosperm development in rice. Our results reveal that FLO24 acts as an important regulator of endosperm development, which might function in maintaining the activities of enzymes involved in starch biosynthesis in rice.

Draft genome sequence of Monascus ruber strain FM39-7.

In China, certain Monascus ruber strains are traditionally used as edible fungi. We sequenced the genome of M. ruber FM39-7 strain, an isolate from fermented rice. The genome is 25.89 Mb with a G + C content of 48.86%, containing 8485 annotated genes.

A toxin-antidote system contributes to interspecific reproductive isolation in rice.

Breakdown of reproductive isolation facilitates flow of useful trait genes into crop plants from their wild relatives. Hybrid sterility, a major form of reproductive isolation exists between cultivated rice (Oryza sativa) and wild rice (O. meridionalis, Mer). Here, we report the cloning of qHMS1, a quantitative trait locus controlling hybrid male sterility between these two species. Like qHMS7, another locus we cloned previously, qHMS1 encodes a toxin-antidote system, but differs in the encoded proteins, their evolutionary origin, and action time point during pollen development. In plants heterozygous at qHMS1, ~ 50% of pollens carrying qHMS1-D (an allele from cultivated rice) are selectively killed. In plants heterozygous at both qHMS1 and qHMS7, ~ 75% pollens without co-presence of qHMS1-Mer and qHMS7-D are selectively killed, indicating that the antidotes function in a toxin-dependent manner. Our results indicate that different toxin-antidote systems provide stacked reproductive isolation for maintaining species identity and shed light on breakdown of hybrid male sterility.

A CYP78As-small grain4-coat protein complex â ¡ pathway promotes grain size in rice.

CYP78A, a cytochrome P450 subfamily that includes rice (Oryza sativa L.) BIG GRAIN2 (BG2, CYP78A13) and Arabidopsis thaliana KLUH (KLU, CYP78A5), generate an unknown mobile growth signal (referred to as a CYP78A-derived signal) that increases grain (seed) size. However, the mechanism by which the CYP78A pathway increases grain size remains elusive. Here, we characterized a rice small grain mutant, small grain4 (smg4), with smaller grains than its wild type due to restricted cell expansion and cell proliferation in spikelet hulls. SMG4 encodes a multidrug and toxic compound extrusion (MATE) transporter. Loss of function of SMG4 causes smaller grains while overexpressing SMG4 results in larger grains. SMG4 is mainly localized to endoplasmic reticulum (ER) exit sites (ERESs) and partially localized to the ER and Golgi. Biochemically, SMG4 interacts with coat protein complex Ⅱ (COPⅡ) components (Sar1, Sec23, and Sec24) and CYP78As (BG2, GRAIN LENGTH 3.2 [GL3.2], and BG2-LIKE 1 [BG2L1]). Genetically, SMG4 acts, at least in part, in a common pathway with Sar1 and CYP78As to regulate grain size. In summary, our findings reveal a CYP78As-SMG4-COPⅡ regulatory pathway for grain size in rice, thus providing new insights into the molecular and genetic regulatory mechanism of grain size.

A natural gene drive system confers reproductive isolation in rice.

Hybrid sterility restricts the utilization of superior heterosis of indica-japonica inter-subspecific hybrids. In this study, we report the identification of RHS12, a major locus controlling male gamete sterility in indica-japonica hybrid rice. We show that RHS12 consists of two genes (iORF3/DUYAO and iORF4/JIEYAO) that confer preferential transmission of the RHS12-i type male gamete into the progeny, thereby forming a natural gene drive. DUYAO encodes a mitochondrion-targeted protein that interacts with OsCOX11 to trigger cytotoxicity and cell death, whereas JIEYAO encodes a protein that reroutes DUYAO to the autophagosome for degradation via direct physical interaction, thereby detoxifying DUYAO. Evolutionary trajectory analysis reveals that this system likely formed de novo in the AA genome Oryza clade and contributed to reproductive isolation (RI) between different lineages of rice. Our combined results provide mechanistic insights into the genetic basis of RI as well as insights for strategic designs of hybrid rice breeding.

The influence of perceptual load on gaze-induced attentional orienting: The modulation of expectation.

Humans tend to focus on others' gaze. Previous studies have shown that the gaze direction of others can induce corresponding attentional orienting. However, gaze cues have typically been presented alone in these studies. It is unclear how gaze cues induce observers' attention in complicated contexts with additional perceptual information. Therefore, the present study investigated gaze-induced attentional orienting at different levels of perceptual load. Results indicated that the attentional effect of the dynamic gaze cue (i.e., GCE: gaze cue effect) emerged under low perceptual load and disappeared under high perceptual load. The absence of GCE could not attribute to perceptual capacity exhaustion. Moreover, the influence of perceptual load on gaze-induced attentional orienting was modulated by individuals' expectation. Specifically, the GCE occurred under high perceptual load when the gaze cue was predictive (with individuals' expectation). These findings provide new evidence on the mode of gaze-induced attentional orienting under different perceptual load conditions.

Young Leaf White Stripe encodes a P-type PPR protein required for chloroplast development.

Pentatricopeptide repeat (PPR) proteins function in post-transcriptional regulation of organellar gene expression. Although several PPR proteins are known to function in chloroplast development in rice (Oryza sativa), the detailed molecular functions of many PPR proteins remain unclear. Here, we characterized a rice young leaf white stripe (ylws) mutant, which has defective chloroplast development during early seedling growth. Map-based cloning revealed that YLWS encodes a novel P-type chloroplast-targeted PPR protein with 11 PPR motifs. Further expression analyses showed that many nuclear- and plastid-encoded genes in the ylws mutant were significantly changed at the RNA and protein levels. The ylws mutant was impaired in chloroplast ribosome biogenesis and chloroplast development under low-temperature conditions. The ylws mutation causes defects in the splicing of atpF, ndhA, rpl2, and rps12, and editing of ndhA, ndhB, and rps14 transcripts. YLWS directly binds to specific sites in the atpF, ndhA, and rpl2 pre-mRNAs. Our results suggest that YLWS participates in chloroplast RNA group II intron splicing and plays an important role in chloroplast development during early leaf development.

ESCRT-III component OsSNF7.2 modulates leaf rolling by trafficking and endosomal degradation of auxin biosynthetic enzyme OsYUC8 in rice.

The endosomal sorting complex required for transport (ESCRT) is highly conserved in eukaryotic cells and plays an essential role in the biogenesis of multivesicular bodies and cargo degradation to the plant vacuole or lysosomes. Although ESCRT components affect a variety of plant growth and development processes, their impact on leaf development is rarely reported. Here, we found that OsSNF7.2, an ESCRT-III component, controls leaf rolling in rice (Oryza sativa). The Ossnf7.2 mutant rolled leaf 17 (rl17) has adaxially rolled leaves due to the decreased number and size of the bulliform cells. OsSNF7.2 is expressed ubiquitously in all tissues, and its protein is localized in the endosomal compartments. OsSNF7.2 homologs, including OsSNF7, OsSNF7.3, and OsSNF7.4, can physically interact with OsSNF7.2, but their single mutation did not result in leaf rolling. Other ESCRT complex subunits, namely OsVPS20, OsVPS24, and OsBRO1, also interact with OsSNF7.2. Further assays revealed that OsSNF7.2 interacts with OsYUC8 and aids its vacuolar degradation. Both Osyuc8 and rl17 Osyuc8 showed rolled leaves, indicating that OsYUC8 and OsSNF7.2 function in the same pathway, conferring leaf development. This study reveals a new biological function for the ESCRT-III components, and provides new insights into the molecular mechanisms underlying leaf rolling.

A regulatory loop establishes the link between the circadian clock and abscisic acid signaling in rice.

There is a close regulatory relationship between the circadian clock and the abscisic acid (ABA) signaling pathway in regulating many developmental processes and stress responses. However, the exact feedback regulation mechanism between them is still poorly understood. Here, we identified the rice (Oryza sativa) clock component PSEUDO-RESPONSE REGULATOR 95 (OsPRR95) as a transcriptional regulator that accelerates seed germination and seedling growth by inhibiting ABA signaling. We also found that OsPRR95 binds to the ABA receptor gene REGULATORY COMPONENTS OF ABA RECEPTORS10 (OsRCAR10) DNA and inhibits its expression. Genetic analysis showed OsRCAR10 acts downstream of OsPRR95 in mediating ABA responses. In addition, the induction of OsPRR95 by ABA partly required a functional OsRCAR10, and the ABA-responsive element-binding factor ABSCISIC ACID INSENSITIVE5 (OsABI5) bound directly to the promoter of OsPRR95 and activated its expression, thus establishing a regulatory feedback loop between OsPRR95, OsRCAR10, and OsABI5. Taken together, our results demonstrated that the OsRCAR10-OsABI5-OsPRR95 feedback loop modulates ABA signaling to fine-tune seed germination and seedling growth, thus establishing the molecular link between ABA signaling and the circadian clock.

Focused attention: its key role in gaze and arrow cues for determining where attention is directed.

Others' gaze direction and traffic arrow signal lights play significant roles in guiding observers' attention in daily life. Previous studies have shown that gaze and arrow cues can direct attention to the cued location. However, it is ambiguous where gaze and arrow cues guide attention: the cued location or a broader cued region. Therefore, the present study adopted a primary cue-target task and manipulated possible target locations to explore this issue. The results revealed that due to the different physical characteristics of non-predictive gaze and arrow cues, physically unfocused-pointing gaze cues guided attention to a broader cued region, whereas focused-pointing arrow cues guided attention to the exact cued location. Furthermore, gaze cues could also direct attention to the exact cued location when observers' attention was focused in a top-down manner (with highly predictive probability). These findings suggest that where gaze and arrow cues direct attention depends on whether observers' attention is focused by the cues, either in a bottom-up or top-down manner. Accordingly, a preliminary framework called the "Focused-Diffused Attentional Orienting Model" is proposed to explain how gaze and arrow cues direct humans' attention. The present study enhances our understanding of human attentional orienting systems from a behavioral perspective.

Anomaly Detection in Satellite Telemetry Data Using a Sparse Feature-Based Method.

Anomaly detection based on telemetry data is a major issue in satellite health monitoring which can identify unusual or unexpected events, helping to avoid serious accidents and ensure the safety and reliability of operations. In recent years, sparse representation techniques have received an increasing amount of interest in anomaly detection, although its applications in satellites are still being explored. In this paper, a novel sparse feature-based anomaly detection method (SFAD) is proposed to identify hybrid anomalies in telemetry. First, a telemetry data dictionary and the corresponding sparse matrix are obtained through K-means Singular Value Decomposition (K-SVD) algorithms, then sparse features are defined from the sparse matrix containing the local dynamics and co-occurrence relations in the multivariate telemetry time series. Finally, lower-dimensional sparse features vectors are input to a one-class support vector machine (OCSVM) to detect anomalies in telemetry. Case analysis based on satellite antenna telemetry data shows that the detection precision, F1-score and FPR of the proposed method are improved compared with other existing multivariate anomaly detection methods, illustrating the good effectiveness of this method.

Dwarf and High Tillering1 represses rice tillering through mediating the splicing of D14 pre-mRNA.

Strigolactones (SLs) constitute a class of plant hormones that regulate many aspects of plant development, including repressing tillering in rice (Oryza sativa). However, how SL pathways are regulated is still poorly understood. Here, we describe a rice mutant dwarf and high tillering1 (dht1), which exhibits pleiotropic phenotypes (such as dwarfism and increased tiller numbers) similar to those of mutants defective in SL signaling. We show that DHT1 encodes a monocotyledon-specific hnRNP-like protein that acts as a previously unrecognized intron splicing factor for many precursor mRNAs (pre-mRNAs), including for the SL receptor gene D14. We find that the dht1 (DHT1I232F) mutant protein is impaired in its stability and RNA binding activity, causing defective splicing of D14 pre-mRNA and reduced D14 expression, and consequently leading to the SL signaling-defective phenotypes. Overall, our findings deepen our understanding of the functional diversification of hnRNP-like proteins and establish a connection between posttranscriptional splicing and SL signaling in the regulation of plant development.

Rice STOMATAL CYTOKINESIS DEFECTIVE2 regulates cell expansion by affecting vesicular trafficking in rice.

Vesicular trafficking plays critical roles in cell expansion in yeast and mammals, but information linking vesicular trafficking and cell expansion in plants is limited. Here, we isolated and characterized a rice (Oryza sativa) mutant, decreased plant height 1-1 (dph1-1), which exhibited a wide spectrum of developmental phenotypes, including reduced plant height and smaller panicles and grains. Cytological analysis revealed that limited cell expansion was responsible for the dph1-1 mutant phenotype compared to the wild-type. Map-based cloning revealed that DPH1 encodes a plant-specific protein, OsSCD2, which is homologous to Arabidopsis (Arabidopsis thaliana) STOMATAL CYTOKINESIS DEFECTIVE2 (SCD2). Subcellular localization revealed that OsSCD2 is associated with clathrin. Confocal microscopy showed that the dph1-1 mutant has defective endocytosis and post-Golgi trafficking. Biochemical and confocal data indicated that OsSCD2 physically interacts with OsSCD1 and that they are associated with intracellular structures that colocalize with microtubules. Furthermore, we found that cellulose synthesis was affected in the dph1-1 mutant, evidenced by reduced cellulose synthase gene accumulation at the transcript and protein levels, most likely resulting from an impaired localization pattern. Our results suggest that OsSCD2 is involved in clathrin-related vesicular trafficking with an important role in maintaining plant growth in rice.

Role of microRNA­218­5p in sevoflurane­induced protective effects in hepatic ischemia/reperfusion injury mice by regulating GAB2/PI3K/AKT pathway.

Hepatic ischemia/reperfusion (I/R) injury (HIRI) often occurs following tissue resection, hemorrhagic shock or transplantation surgery. Previous investigations showed that sevoflurane (Sevo), an inhalation anesthetic, had protective properties against different organ damage in animal models including HIRI. This study is aimed to investigate the underlying mechanisms involved in the protective effects of Sevo on HIRI. The present study results showed that treatment with Sevo improved histologic damage, inflammatory response, oxidative stress and apoptosis after hepatic I/R, indicating the protective role of Sevo against liver I/R injury. Importantly, in order to determine the molecular mechanism of Sevo in HIRI, the focus of the study was on microRNA (miR) regulation. By retrieving the microarray data in the Gene Expression Omnibus dataset (GSE72315), miR­218­5p was found to be significantly downregulated by Sevo. Moreover, miR­218­5p overexpression using agomiR­218­5p reversed the protective roles of Sevo against HIRI. Furthermore, GAB2, a positive regulator of PI3K/AKT signaling pathway, was found as a target gene of miR­218­5p. It was also found that the Sevo­mediated protective effects may be dependent on the activation of GAB2/PI3K/AKT. Collectively, these data revealed that Sevo alleviated HIRI in mice by restraining apoptosis, relieving oxidative stress and inflammatory response through the miR­218­5p/GAB2/PI3K/AKT pathway, which helps in understanding the novel mechanism of the hepatic­protection of Sevo.

Genetic characterization and fine mapping of qHMS4 responsible for pollen sterility in hybrids between Oryza sativa L. and Oryza glaberrima Steud.

African cultivated rice (Oryza glaberrima Steud) contains many favorable genes for tolerance to biotic and abiotic stresses and F1 hybrids between Asian cultivated rice (Oryza sativa L.) show strong heterosis. However, the hybrids of two species often exhibit hybrid sterility. Here, we identified a male sterility locus qHMS4 on chromosome 4 (Chr.4), which induces pollen semi-sterility in F1 hybrids of japonica rice variety Dianjingyou1 (DJY1) and a near-isogenic line (NIL) carrying a Chr.4 segment from Oryza glaberrima accession IRGC101854. Cytological observations indicated that non-functional pollen grains produced by the hybrids and lacking starch accumulation abort at the late bicellular stage. Molecular genetic analysis revealed distorted segregation in male gametogenesis carrying qHMS4 allele from DJY1. Fine-mapping of qHMS4 using an F2 population of 22,500 plants delimited qHMS4 to a region of 110-kb on the short arm of Chr.4. Sequence analysis showed that the corresponding sequence region in DJY1 and Oryza glaberrima were 114-kb and 323-kb, respectively, and that the sequence homology was very poor. Gene prediction analysis identified 16 and 46 open reading frames (ORFs) based on the sequences of DJY1 and O. glaberrima, respectively, among which 3 ORFs were shared by both. Future map-based cloning of qHMS4 will help to understand the underlying molecular mechanism of hybrid sterility between the two cultivated rice species. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-022-01306-8.

Determinant Factors and Regulatory Systems for Anthocyanin Biosynthesis in Rice Apiculi and Stigmas.

Anthocyanins cause purple, brown or red colors in various tissues of rice plants, but the specific determinant factors and regulatory systems for anthocyanin biosynthesis in almost all tissues remain largely unknown. In the present study, we mapped and isolated two complementary genes, OsC1 encoding a R2R3-MYB transcriptional factor and OsDFR encoding a dihydroflavonol 4-reductase, which are responsible for the purple coloration of apiculi and stigmas in indica cultivar Xieqingzao by the map-based cloning strategy. We also identified two tissue-specific pigmentation genes, OsPa for apiculi and OsPs for stigmas, by phylogenetic analysis of all anthocyanin biosynthesis-associated bHLH transcriptional factors in maize and rice, CRISPR/Cas9 knockout and transcriptional expression analysis. The OsC1, OsPa and OsPs proteins are all localized in the nucleus while the OsDFR protein is localized in the nucleus and cytoplasm, and the OsC1 and OsDFR genes are preferentially strongly expressed in both purple-colored tissues while the OsPa and OsPs genes are preferentially strongly expressed in apiculi and stigmas, respectively. OsC1 specifically interacts with OsPa or OsPs to activate OsDFR and other anthocyanin biosynthesis genes, resulting in purple-colored apiculi or stigmas. OsC1 itself does not produce color but can produce brown apiculi when functioning together with OsPa. Loss of function of OsDFR alone leads to brown apiculi and straw-white stigmas. Genotyping and phenotyping of a panel of 176 rice accessions revealed diverse genotypic combinations of OsC1, OsDFR, OsPa and OsPs that enable accurate prediction of their apiculus and stigma pigmentation phenotypes, thus validating the general applicability of the OsC1-OsDFR-OsPa and OsC1-OsDFR-OsPs models to natural populations. Our findings disclosed the biological functions of OsC1, OsPa and OsPs, and shed light on the specific regulatory systems of anthocyanin biosynthesis in apiculi and stigmas, a further step in understanding the regulatory network of anthocyanin biosynthesis in rice.