DNAL7, a new allele of NAL11, has major pleiotropic effects on rice architecture.

MAIN CONCLUSION: dnal7, a novel allelic variant of the OsHSP40, affects rice plant architecture and grain yield by coordinating auxins, cytokinins, and gibberellic acids. Plant height and leaf morphology are the most important traits of the ideal plant architecture (IPA), and discovering related genes is critical for breeding high-yield rice. Here, a dwarf and narrow leaf 7 (dnal7) mutant was identified from a γ-ray treated mutant population, which exhibits pleiotropic effects, including dwarfing, narrow leaves, small seeds, and low grain yield per plant compared to the wild type (WT). Histological analysis showed that the number of veins and the distance between adjacent small veins (SVs) were significantly reduced compared to the WT, indicating that DNAL7 controls leaf size by regulating the formation of veins. Map-based cloning and transgenic complementation revealed that DNAL7 is allelic to NAL11, which encodes OsHSP40, and the deletion of 2 codons in dnal7 destroyed the His-Pro-Asp (HPD) motif of OsHSP40. In addition, expression of DNAL7 in both WT and dnal7 gradually increased with the increase of temperature in the range of 27-31 °C. Heat stress significantly affected the seedling height and leaf width of the dnal7 mutant. A comparative transcriptome analysis of WT and dnal7 revealed that DNAL7 influenced multiple metabolic pathways, including plant hormone signal transduction, carbon metabolism, and biosynthesis of amino acids. Furthermore, the contents of the cytokinins in leaf blades were much higher in dnal7 than in the WT, whereas the contents of auxins were lower in dnal7. The contents of bioactive gibberellic acids (GAs) including GA1, GA3, and GA4 in shoots were decreased in dnal7. Thus, DNAL7 regulates rice plant architecture by coordinating the balance of auxins, cytokinins, and GAs. These results indicate that OsHSP40 is a pleiotropic gene, which plays an important role in improving rice yield and plant architecture.

1The harm of residual plastic film and its accumulation driving factors in northwest China.

The background to this research is stark and rather troubling: the ongoing accumulation of residual plastic film (RPF) in farmland ultimately threatens the sustainable development of agriculture and food security. In this study, we selected 15 counties in northern China to analyze the effect of RPF content on soil properties and crop yield and the driving factors through sampling and survey questionnaire. The linear mixed-effects model revealed the four main factors affecting RPF content, ranked as follows: plastic film mulching years > government recycling policy > spacing between rows > recycling methods (0.47493 > 0.25635 > 0.23380 > 0.17001). The contribution value of plastic film thickness was very low (R2(M) = 0.099). The plastic film width and spacing within rows did not significantly affect RPF content. The structural equation model showed that the RPF had both direct (-0.111) and indirect (-0.010) effects on maize yield. A 1 kg ha-1 increase in RPF content decreased maize yield by 27.67 kg ha-1. RPF did not directly affect soil organic carbon (SOC), pH, or ammonium nitrogen. RPF mainly aggravated soil salinization by increasing soil nitrate-nitrogen, available phosphorus, and available potassium, increasing SOC and decreasing pH, thus reducing crop yield. To the best of our knowledge, this is the first study to combine the driving factors of RPF accumulation and the effects of RPF on soil properties and crop yield in a large-scale sampling and survey questionnaire. RPF accumulation in the study area has aggravated soil salinization and reduced crop yields. Hence, measures are needed to alleviate the current situation. Local governments should formulate RPF recovery policies based on their actual situation. At the national level, more research is needed to develop RPF recovery machinery to improve efficiency.

Development of InDel markers for Oryza sativa ssp. javanica based on whole-genome resequencing.

Oryza sativa ssp. javanica rice varieties exhibit a wide variation in the phenotypes of several important agronomic traits, including grain quality, grain shape, plant architecture, disease resistance, and high adaption to an unfavorable environment, indicating a great potential for rice improvement. DNA molecular markers are basic and critical tools in genetic analysis and gene mining. However, only a few whole-genome variation analyses have been performed in Oryza sativa ssp. Javanica (tropical japonica rice), and this has hampered the utilization of such an important resource. In this study, the length of insertions/deletions variation greater larger than 10 bp from 10 Oryza sativa ssp. indica rice and 10 Oryza sativa ssp. tropical japonica rice were extracted by using the Nipponbare genome as a reference. A total of 118 primer pairs which were almost evenly distributed on each chromosome corresponding to the loci of InDels were designed by the Primer 5 program. We confirmed 85 InDel markers from 60 rice varieties, including indica and tropical japonica, by running polyacrylamide gels. The InDel markers function like SSRs in identifying hybrids, calculating genetic distance, constructing the genetic linkage map, and gene mining. The InDel markers developed in this study might help in genetic studies and to investigate the tropical japonica rice varieties.

Whole Genome Resequencing of 20 Accessions of Rice Landraces Reveals Javanica Genomic Structure Variation and Allelic Genotypes of a Grain Weight Gene TGW2.

The landraces preserved by indigenous worldwide exhibited larger variation in the phenotypes and adaption to different environments, which suggests that they comprise rich resources and can be served as a gene pool for rice improvement. Despite extensive studies on cultivated rice, the variations and relationships between landraces and modern cultivated rice remain unclear. In this study, a total of 20 varieties that include 10 Oryza javanica collected from different countries worldwide and 10 Oryza indica from China were genotyped and yielded a sum of 99.9-Gb resequencing raw data. With the genomic sequence of the japonica cultivar Nipponbare as a reference, the following genetic features of single-nucleotide polymorphism (SNP) ranged from 861,177 to 1,044,617, insertion-deletion polymorphisms (InDels) ranged from 164,018 to 211,135, and structural variation (SV) ranged from 3,313 to 4,959 were identified in Oryza javanica. Variation between the two subspecies was also determined that 584,104 SNPs, 75,351 InDels, 104,606 SNPs, and 19,872 InDels specific to Oryza indica and Oryza javanica, respectively. Furthermore, Gene Ontology (GO) and KEGG of Oryza javanica-specific SNP-related genes revealed that they participated in DNA metabolic process, DNA replication, and DNA integration. The sequence variation and candidate grain shape-related gene TGW2 were identified through Fst and sweep selective analysis. Hap4 of TGW2 is performed better than others. The whole genome sequence data and genetic variation information illustrated in this study will serve as an important gene pool for molecular breeding and facilitate genetic analysis of Oryza javanica varieties.

Natural variation of HTH5 from wild rice, Oryza rufipogon Griff., is involved in conferring high-temperature tolerance at the heading stage.

Global warming is a major abiotic stress factor, which limit rice production. Exploiting the genetic basis of the natural variation in heat resistance at different reproductive stages among diverse exotic Oryza germplasms can help breeding heat-resistant rice cultivars. Here, we identified a stable quantitative trait locus (QTL) for heat tolerance at the heading stage on chromosome 5 (qHTH5) in O. rufipogon Griff. The corresponding gene, HTH5, pertains to the pyridoxal phosphate-binding protein PLPBP (formerly called PROSC) family, which is predicted to encode pyridoxal phosphate homeostasis protein (PLPHP) localized to the mitochondrion. Overexpression of HTH5 increased the seed-setting rate of rice plants under heat stress at the heading stage, whereas suppression of HTH5 resulted in greater susceptibility to heat stress. Further investigation indicated that HTH5 reduces reactive oxygen species accumulation at high temperatures by increasing the heat-induced pyridoxal 5'-phosphate (PLP) content. Moreover, we found that two SNPs located in the HTH5 promoter region are involved with its expression level and associated with heat tolerance diversity. These findings suggest that the novel gene HTH5 might have great potential value for heightening rice tolerance to heat stress to the on-going threat of global warming.

Layer-by-layer assembly of nanocomposite interlayers on a kaolin substrate for enhancing membrane performance of Pb(II) and Cd(II) removal.

Developing an ultra-thin polyamide selective layer with sufficient mechanical robustness on a highly porous ceramic substrate is challenging for removing heavy metal ions from wastewater. We synthesized a reliable ceramic-polyamide membrane by assembling nanocomposite interlayers of alumina and carbon black on the kaolin substrate. The surface morphology, pore size distribution, and roughness of ceramic substrates were improved by introducing the nanocomposite interlayer. The corresponding optimized water flux, Pb(II), and Cd(II) removal efficiency are 2.75 L m-2 h-1, 98.44%, and 97.51%, respectively, which are better than those of the polyamide films constructed directly on the ceramic substrate. This facile structure provides more active sites for forming ultrathin polyamide layers with satisfactory mechanical robustness. This paper provides a new perspective for fabricating efficient heavy metal ions filters.

Heavy metal ions and particulate pollutants can be effectively removed by a gravity-driven ceramic foam filter optimized by carbon nanotube implantation.

It is of great significance to develop a new gravity-driven filter to remove water pollutants, but it is still challenging. Here, a novel and simple strategy is demonstrated to manufacture fly ash (FA) ceramic foams showing a three-dimensional interconnected porous structure, with multiwalled carbon nanotubes (MWCNTs) implanted by combining carbamate grafting and polydimethylsiloxane coating. The polydimethylsiloxane formed a physical coating on the carbamate group, generating an effective thermal insulating layer on the outer side of the entire MWCNT. The FA foam, which shows a sufficient adsorption capacity for Pb(II) (51.67 ± 1.17 mg g-1) and Cd(II) (30.12 ± 0.37 mg g-1) at pH = 5, T = 25 °C, has a 96.33%, 95.12%, 89.50% removal efficiency for Cd(II), Pb(II), and particulate pollutants, and exhibits excellent recycling performance. This paper provides new opportunities to fabricate gravity-driven filters with low energy consumption for wastewater treatment.

Comparison of methane metabolism in the rhizomicrobiomes of wild and related cultivated rice accessions reveals a strong impact of crop domestication.

Microbial communities from rhizosphere (rhizomicrobiomes) have been significantly impacted by domestication as evidenced by a comparison of the rhizomicrobiomes of wild and related cultivated rice accessions. While there have been many published studies focusing on the structure of the rhizomicrobiome, studies comparing the functional traits of the microbial communities in the rhizospheres of wild rice and cultivated rice accessions are not yet available. In this study, we used metagenomic data from experimental rice plots to analyze the potential functional traits of the microbial communities in the rhizospheres of wild rice accessions originated from Africa and Asia in comparison with their related cultivated rice accessions. The functional potential of rhizosphere microbial communities involved in alanine, aspartate and glutamate metabolism, methane metabolism, carbon fixation pathways, citrate cycle (TCA cycle), pyruvate metabolism and lipopolysaccharide biosynthesis pathways were found to be enriched in the rhizomicrobiomes of wild rice accessions. Notably, methane metabolism in the rhizomicrobiomes of wild and cultivated rice accessions clearly differed. Key enzymes involved in methane production and utilization were overrepresented in the rhizomicrobiome samples obtained from wild rice accessions, suggesting that the rhizomicrobiomes of wild rice maintain a different ecological balance for methane production and utilization compared with those of the related cultivated rice accessions. A novel assessment of the impact of rice domestication on the primary metabolic pathways associated with microbial taxa in the rhizomicrobiomes was performed. Results indicated a strong impact of rice domestication on methane metabolism; a process that represents a critical function of the rhizosphere microbial community of rice. The findings of this study provide important information for future breeding of rice varieties with reduced methane emission during cultivation for sustainable agriculture.

Strategies and Structure Feature of the Aboveground and Belowground Microbial Community Respond to Drought in Wild Rice (Oryza longistaminata).

BACKGROUND: Drought is global environmental stress that limits crop yields. Plant-associated microbiomes play a crucial role in determining plant fitness in response to drought, yet the fundamental mechanisms for maintaining microbial community stability under drought disturbances in wild rice are poorly understood. We make explicit comparisons of leaf, stem, root and rhizosphere microbiomes from the drought-tolerant wild rice (Oryza longistaminata) in response to drought stress. RESULTS: We find that the response of the wild rice microbiome to drought was divided into aboveground-underground patterns. Drought reduced the leaf and stem microbial community diversity and networks stability, but not that of the roots and rhizospheres. Contrary to the aboveground microbial networks, the drought-negative response taxa exhibited much closer interconnections than the drought-positive response taxa and were the dominant network hubs of belowground co-occurrence networks, which may contribute to the stability of the belowground network. Notably, drought induces enrichment of Actinobacteria in belowground compartments, but not the aboveground compartment. Additionally, the rhizosphere microbiome exhibited a higher proportion of generalists and broader habitat niche breadth than the microbiome at other compartments, and drought enhanced the proportion of specialists in all compartments. Null model analysis revealed that both the aboveground and belowground-community were governed primarily by the stochastic assembly process, moreover, drought decreased 'dispersal limitation', and enhanced 'drift'. CONCLUSIONS: Our results provide new insight into the different strategies and assembly mechanisms of the above and belowground microbial community in response to drought, including enrichment of taxonomic groups, and highlight the important role of the stochastic assembly process in shaping microbial community under drought stress.

Comparison of wild rice (Oryza longistaminata) tissues identifies rhizome-specific bacterial and archaeal endophytic microbiomes communities and network structures.

Compared with root-associated habitats, little is known about the role of microbiota inside other rice organs, especially the rhizome of perennial wild rice, and this information may be of importance for agriculture. Oryza longistaminata is perennial wild rice with various agronomically valuable traits, including large biomass on poor soils, high nitrogen use efficiency, and resistance to insect pests and disease. Here, we compared the endophytic bacterial and archaeal communities and network structures of the rhizome to other compartments of O. longistaminata using 16S rRNA gene sequencing. Diverse microbiota and significant variation in community structure were identified among different compartments of O. longistaminata. The rhizome microbial community showed low taxonomic and phylogenetic diversity as well as the lowest network complexity among four compartments. Rhizomes exhibited less phylogenetic clustering than roots and leaves, but similar phylogenetic clustering with stems. Streptococcus, Bacillus, and Methylobacteriaceae were the major genera in the rhizome. ASVs belonging to the Enhydrobacter, YS2, and Roseburia are specifically present in the rhizome. The relative abundance of Methylobacteriaceae in the rhizome and stem was significantly higher than that in leaf and root. Noteworthy type II methanotrophs were observed across all compartments, including the dominant Methylobacteriaceae, which potentially benefits the host by facilitating CH4-dependent N2 fixation under nitrogen nutrient-poor conditions. Our data offers a robust knowledge of host and microbiome interactions across various compartments and lends guidelines to the investigation of adaptation mechanisms of O. longistaminata in nutrient-poor environments for biofertilizer development in agriculture.

An effective method for improving the permeation flux of a ceramic membrane: Single-matrix spherical ceramic membrane.

A single-matrix hydrophobic ceramic membrane (HCM) was prepared via gel-casting and membrane grafting. Fly ash cenospheres and 1H,1H,2H,2H-perfluorooctyl trichlorosilane were used as the single-matrix material. The results showed that when the sintering temperature was 1300℃, the porosity was 75.56 %, and flexural strength was 11.1 MPa; this means that the material meets the requirements for mechanical properties. After grafting 1H,1H,2H,2H-perfluorooctane trichlorosilane, the Si-CH3 peak increased and the Si-OH peak was weaker. Also, the contact angle of the droplet increased from 56° to 126°, and this indicates that the droplet was successfully chemically adsorbed to the surface of the ceramic membrane. The results of computational fluid dynamics simulation show that a gaussian spherical wall greatly improved the permeation flux of foamed ceramic membranes, and the permeation flux of the microchannel increased by 26.5 %∼76.2 % at the same transmembrane pressure. Pure water permeation flux and heavy metal adsorption experiments shows excellent high permeation flux and satisfactory heavy metal adsorption performance of HCM. From the perspective of membrane cost, HCM is suitable to be promoted. In summary, HCM has the potential for commercial application.

Fine mapping of the qHTB1-1QTL, which confers heat tolerance at the booting stage, using an Oryza rufipogon Griff. introgression line.

KEY MESSAGE: The qHTB1-1 QTL, controlling heat tolerance at the booting stage in rice, was fine mapped to a 47.1 kb region containing eight candidate genes. Two positional candidate genes showed significant changes in expression levels under heat stress. High-temperature stress at the booting stage has the potential to significantly limit rice production. An interspecific advanced backcrossed population between the Oryza sativa L. cultivar R53 and the wild Oryza rufipogon Griff accession HHT4 was used as the source material to develop a set of chromosome segment introgression lines to elucidate the genetic mechanism of the qHTB1-1 QTL in heat tolerance. A single-chromosome-segment introgression line, IL01-15, was used to develop secondary populations for the mapping of qHTB1-1 on chromosome 1 for heat tolerance at the booting stage. Using the BC5F2, BC5F3, and BC5F4 populations, we first confirmed qHTB1-1 and validated the phenotypic effect. The qHTB1-1 QTL explained 13.1%, 16.9%, and 17.8% of the phenotypic variance observed in the BC5F2, BC5F3, and BC5F4 generations, respectively. Using homozygous recombinants screened from larger BC6F2 and BC6F3 populations, qHTB1-1 was fine mapped within a 47.1 kb region between markers RM11633 and RM11642. Eight putative predicted genes were annotated in the region, and six genes were predicted to encode expressed proteins. The expression patterns of these six genes demonstrated that LOC_Os01g53160 and LOC_Os01g53220 were highly induced by heat stress in IL01-15 compared to R53. Sequence comparison of the gene-coding regions of LOC_Os01g53160 and LOC_Os01g53220 between R53 and IL01-15 revealed one synonymous and two nonsynonymous SNPs in exons, respectively. Our results provide a basis for identifying the genes underlying qHTB1-1 and indicate that markers linked to the qHTB1-1 locus can be used to improve the heat tolerance of rice at the booting stage by marker-assisted selection.

Effects of external Mn2+ activities on OsNRAMP5 expression level and Cd accumulation in indica rice.

Manganese (Mn) transporter OsNRAMP5 was widely reported to regulate cadmium (Cd) uptake in rice. However, the relationship between OsNRAMP5 expression level and Cd accumulation, impacts of external ion activities on OsNRAMP5 expression level and Cd accumulation are still unclear. Investigations of the relationship between OsNRAMP5 expression level and Cd accumulation in three indica rice genotypes were conducted under various external Mn2+ activities ranging from Mn deficiency to toxicity in EGTA-buffered nutrient solution. Results in this work indicated that OsNRAMP5 expression level in roots significantly up-regulated at Mn phytotoxicity compared to that at Mn deficiency, which may stimulate by the increasing uptake of Mn. Our work also demonstrated that root Cd concentration of all the tested rice decreased notably when external Mn2+ activity reached the level of toxicity. This may explain by the increasing competition between the excess Mn2+ and Cd2+ as well as the disorder of element absorption caused by root damage at Mn toxicity. Our work also revealed that the relationship between OsNRAMP5 expression level in roots and Cd accumulation in roots was insignificant for all the tested genotypes. Besides, OsNRAMP5 expression level in roots seemed more related to root Mn accumulation. The fact that function of OsNRAMP5 mainly focuses on Mn uptake, together with the fact that many transporter genes involved in Cd uptake might result in the insignificant correlation between OsNRAMP5 expression level and Cd accumulation in roots. At last, multi-level regulating and processing of the process from gene expression to protein translation might account for the inconsistent relationship between root OsNRAMP5 expression level and Cd accumulation in roots.

GmFAD3A, A ω-3 Fatty Acid Desaturase Gene, Enhances Cold Tolerance and Seed Germination Rate under Low Temperature in Rice.

Low temperature is an environmental stress factor that is always been applied in research on improving crop growth, productivity, and quality of crops. Polyunsaturated fatty acids (PUFAs) play an important role in cold tolerance, so its genetic manipulation of the PUFA contents in crops has led to the modification of cold sensitivity. In this study, we over-expressed an ω-3 fatty acid desaturase from Glycine max (GmFAD3A) drove by a maize ubiquitin promoter in rice. Compared to the wild type (ZH11), ectopic expression of GmFAD3A increased the contents of lipids and total PUFAs. Seed germination rates in GmFAD3A transgenic rice were enhanced under low temperature (15 °C). Moreover, cold tolerance and survival ratio were significantly improved in GmFAD3A transgenic seedlings. Malondialdehyde (MDA) content in GmFAD3A transgenic rice was lower than that in WT under cold stress, while proline content obviously increased. Meanwhile, the activities of superoxide dismutase (SOD), hydroperoxidase (CAT), and peroxidase (POD) increased substantially in GmFAD3A transgenic rice after 4 h of cold treatment. Taken together, our results suggest that GmFAD3A can enhances cold tolerance and the seed germination rate at a low temperature in rice through the accumulation of proline content, the synergistic increase of the antioxidant enzymes activity, which finally ameliorated the oxidative damage.

Study on Permeability Stability of Sand-Based Microporous Ceramic Filter Membrane.

The instability of diafiltration is a widespread problem in the practical application of microporous ceramic filtration membranes. In this paper, a series of microporous ceramic filter membranes were prepared using inexpensive standard sand and river sand as matrix materials. Semi-empirical formula for the effective permeability radius of ceramic membranes with respect to time was established from analysis of the response mechanism between water flow and material properties. Finally, on the basis of theoretical analysis, some measures were proposed to improve permeate flux. The experimental results showed that during the initial stage of filtration, the microporous ceramic filter membrane had a large change in permeate flux, and during the late stage of filtration, permeate flux tended to be stable. Over time, open porosity and closed porosity changed the actual seepage area of the ceramic membrane, and this affected the stability of permeate flux and final stable permeate flux. The roughness of the inner wall of microporous ceramic pores affected the hydraulic loss coefficient, and this controlled the outflow process. Trace elements that were rich in sand produced a large amount of glass phase after sintering. The glass phase was rich in polar groups and formed a temporary hydrogen bond with the small flow of water molecules. It led to an increase in viscous resistance effect of the side wall along the water flow and the extent of the permeate flux of the ceramic membrane changed with time.

Mechanisms and uncertainties of Zn supply on regulating rice Cd uptake.

Application of Zinc (Zn) is considered an effective measure to reduce Cadmium (Cd) uptake and toxicity in Cd-contaminated soils for many plant species. However, interaction between Zn and Cd in rice plant is complex and uncertain. In this study, four indica rice cultivars were selected to evaluate the effect of Zn exposure in an EGTA-buffered nutrient solution under varying Zn activities and a field level of Cd activity to characterize the interaction between Zn and Cd in rice. Severe depression in shoots' biomass, tiller number, and SPAD (Soil and Plant Analyzer Development) value were found at both Zn deficiency and Zn phytotoxicity levels among four tested rice cultivars. There existed a strong antagonism interaction between Zn and Cd in both shoot and root from Zn deficiency to Zn phytotoxicity. The reduction of Cd accumulation in roots and shoots could be explained by the competition between Zn and Cd as well as the dilution effect of increasing biomass. The conflicting effect of Zn supply on Cd uptake may be attributed to the increasing transfer ratio of Cd from root to shoot with the increasing Zn2+ activities and the strong depression of Fe and Mn in shoots with the increasing Zn2+ activities as well as the variation of genotypes. Balance between Zn and Cd should be considered in field application.

Comparative proteomic analysis of Methanothermobacter thermautotrophicus reveals methane formation from H2 and CO2 under different temperature conditions.

The growth of all methanogens is limited to a specific temperature range. However, Methanothermobacter thermautotrophicus can be found in a variety of natural and artificial environments, the temperatures of which sometimes even exceed the temperature growth ranges of thermophiles. As a result, the extent to which methane production and survival are affected by temperature remains unclear. To investigate the mechanisms of methanogenesis that Archaea have evolved to cope with drastic temperature shifts, the responses of Methanothermobacter thermautotrophicus to temperature were investigated under a high temperature growth (71°C) and cold shock (4°C) using Isobaric tags for relative and absolute quantitation (iTRAQ). The results showed that methane formation is decreased and that protein folding and degradation are increased in both high- and low-temperature treatments. In addition, proteins predicted to be involved in processing environmental information processing and in cell membrane/wall/envelope biogenesis may play key roles in affecting methane formation and enhancing the response of M. thermautotrophicus to temperature stress. Analysis of the genomic locations of the genes corresponding to these temperature-dependent proteins predicted that 77 of the genes likely to form 32 gene clusters. Here, we assess the response of M. thermautotrophicus to different temperatures and provide a new level of understanding of methane formation and cellular putative adaptive responses.

Over-expression of a protein disulfide isomerase gene from Methanothermobacter thermautotrophicus, enhances heat stress tolerance in rice.

High temperature (HT) stress is a major environmental stress that limits agricultural production worldwide. Discovery and application of genes promoting high temperature tolerance is essential to enhance crop tolerance to heat stress. Proteins associated with chaperone and protein folding plays an important role in the high temperature stress response of plants. MTH1745 (MtPDI), a disulfide isomerase-like protein (PDI) with a chaperone function and disulfide isomerase activity from Methanothermobacter thermautotrophicus delta H, was selected for studying the heat stress tolerance using an ectopic expression method in rice. Through molecular identification via quantitative real-time PCR and western blot, we demonstrated that the MtPDI gene was expressed stably in transgenic rice. Heat stress tolerance and survival ratio were significantly improved in seedling transgenic rice. At the same time, proline content, superoxide dismutase (SOD) and peroxidase (POD) activities were increased in MtPDI transgenic rice with a reduced malondialdehyde (MDA) content. Moreover, increased content of thiols group was discovered in transgenic plants. These results indicate that heterologous expression of MtPDI from extremophiles could confer heat stress tolerance of transgenic rice through the accumulation of proline content, the synergistic increase of the antioxidant enzymes activity and elevated production of more thiols group, which finally ameliorated the oxidative damage.

The E3 Ubiquitin Ligase HAF1 Modulates Circadian Accumulation of EARLY FLOWERING3 to Control Heading Date in Rice under Long-Day Conditions.

The ubiquitin 26S proteasome system (UPS) is critical for enabling plants to alter their proteomes to integrate internal and external signals for the photoperiodic induction of flowering. We previously demonstrated that HAF1, a C3HC4 RING domain-containing E3 ubiquitin ligase, is essential to precisely modulate the timing of Heading Date1 accumulation and to ensure appropriate photoperiodic responses under short-day conditions in rice (Oryza sativa). However, how HAF1 mediates flowering under long-day conditions remains unknown. In this study, we show that OsELF3 (EARLY FLOWERING3) is the direct substrate of HAF1 for ubiquitination in vitro and in vivo. HAF1 is required for maintaining the circadian rhythm of OsELF3 accumulation during photoperiodic responses in rice. In addition, the haf1 oself3 double mutant headed as late as oself3 plants under long-day conditions. An amino acid variation (L558S) within the interaction domain of OsELF3 with HAF1 greatly contributes to the variation in heading date among japonica rice accessions. The japonica accessions carrying the OsELF3(L)-type allele are found at higher latitudes, while varieties carrying the OsELF3(S)-type allele are found at lower latitudes. Taken together, our findings suggest that HAF1 precisely modulates the diurnal rhythm of OsELF3 accumulation to ensure the appropriate heading date in rice.

The chimeric mitochondrial gene orf182 causes non-pollen-type abortion in Dongxiang cytoplasmic male-sterile rice.

D1-cytoplasmic male sterility (CMS) rice is a sporophytic cytoplasmic male-sterile rice developed from Dongxiang wild rice that exhibits a no-pollen-grain phenotype. A mitochondrial chimeric gene (orf182) was detected by mitochondrial genome sequencing and a comparative analysis. Orf182 is composed of three recombinant fragments, the largest of which is homologous to Sorghum bicolor mitochondrial sequences. In addition, orf182 was found only in wild rice species collected from China. Northern blot analysis showed that orf182 transcripts were affected by Rf genes in the isocytoplasmic restorer line DR7. Western blot analysis showed that the ORF182 product was localized in the mitochondria of the CMS line. An expression cassette containing orf182 fused to a mitochondrial transit peptide induced the maintainer line of male sterility, which lacked pollen grains in the anthers. Furthermore, the in vivo expression of orf182 also inhibited the growth of Escherichia coli, with lower respiration rate, excess accumulation of reactive oxygen species and decreased ATP levels. We conclude that the mitochondrial chimeric gene orf182 possesses a unique structure and origin differing from other identified mitochondrial CMS genes, and this gene is connected to non-pollen type of sporophytic male sterility in D1-CMS rice.