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Rice production worldwide has continued to decline due to various environmental stresses, with drought stress being a prominent factor, as rice is a semi-aquatic plant. Thus, development of drought stress-resistant rice varieties is of great importance for rice production. In our previous study, we found that microRNAs (miRNAs) play a crucial role in the response to drought stress in Dongxiang wild rice (DXWR) (Oryza rufipogon Griff.). Developing drought stress-responsive miRNA-based single sequence repeat (SSR) markers for DXWR will be of great value for the efficient identification and utilization of miRNA genes to breed drought stress-resistant rice varieties. In this study, ninety-nine novel SSR markers were developed based on the drought stress-responsive miRNAs of DXWR. These markers were distributed in all 12 rice chromosomes, and most were in chromosomes 2 and 6, with di- and tri-nucleotides being the most abundant repeat motifs. Twelve out of fourteen synthesized markers displayed high levels of genetic diversity in the genomes of three populations of DXWR and 40 modern rice varieties worldwide. The number of alleles per locus ranged from 2 to 7, with an average of 4.67; the genetic diversity index ranged from 0.21 to 0.76, with an average of 0.58; and the polymorphism information content value ranged from 0.18 to 0.72, with an average of 0.53. These novel molecular markers developed from the drought stress-responsive miRNAs of DXWR could be additional tools for mapping elite miRNA genes and breeding drought stress-resistant rice varieties. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) grain hull color is an easily observable trait and regarded as a crucial morphological marker in rice breeding. Here, a purple gradient grain hull mutant (pg) was found from natural mutations of a straw-white grain hull rice variety IARI 6184B (Orzya sativa L. subsp. indica). The color of the mutant grain hulls changed from straw-white to pink, then purple, and finally brownish-yellow. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) identified 217 flavonoids, including 18 anthocyanins, among which cyanidin O-syringic acid had the highest concentration in pink (66.2 × 106) and purple (68.0 × 106) grain hulls. The relative contents of hesperetin O-malonyl-hexoside, apigenin derivatives, genistein derivatives, and kaempferol 3-O derivatives were consistently downregulated during pg grain hull development. Conversely, 12 anthocyanins were upregulated in colored hulls, and cyanidin 3-O-malonylhexoside was abundant only in pink and purple grain hulls. Moreover, the candidate gene was mapped into a 1.38 Mb region on chromosome 4 through bulked segregant analysis based on deep sequencing (BSA-seq) and gene mapping approaches. These results increased our understanding of anthocyanin biosynthesis in rice grains, helping rice breeders to select new rice varieties with desirable grain traits. [ABSTRACT FROM AUTHOR]

Salt stress is one of the most devastating abiotic stresses for global rice production. The conserved miR1861 family has been shown to participate in the control of plant growth, development, and response to abiotic stresses. However, no reports have focused yet on the roles of miR1861 in the salt stress responses. In a previous study, the member miR1861h was identified in Dongxiang wild rice (DXWR, Oryza rufipogon Griff.) with small RNA sequencing. In this study, we found that the expression level of miR1861h increased significantly under salt stress. Then, we generated transgenic plants overexpressing miR1861h under control of the CaMV35S promoter, and verified miR1861h expression using qRT-PCR analysis. We found that miR1861h overexpression increased plant salt stress tolerance significantly, as evidenced by higher survival rates. Analysis of putative targets and cis-acting elements further suggested that miR1861h could be a positive regulator of plant tolerance to salt stress. Taken together, our findings provide more insight into the roles of miR1861 family. [ABSTRACT FROM AUTHOR]

Dendrobium officinale K. Kimura et Migo is an endangered and valuable medicinal herb. In order to understand the origin of D. officinale cultivars and the differences in germplasm resources, 81 D. officinale individuals including wild-collected, market-collected, and two germplasm resources from Zhejiang and Jiangxi province was scanned with 75 EST-SSRs. The number of alleles detected at each locus ranged from 1 to 14 with an average of 3.703. The mean expected heterozygosity (0.492), and Shannon's information index (0.915) indicated a high level of hybridization rate among the individuals tested. Principal component analysis and cluster analysis based on UPGMA illustrated that almost all the germplasm resources from Jiangxi were grouped together, then the germplasm resources from Zhejiang, wild-collected and market-collected were divided into three clusters, indicated that the origin of market-collected individuals were derived from Zhejiang and the germplasm resources from Jiangxi were well preserved and waited for development. Eight recovered sequences of fructose-bisphosphate aldolase 1 from wild-collected and two germplasm resources showed that the similarity of these sequences ranged from 71.15 to 93.42%, and base insertion, deletion and base varieties occurred in almost all the 7 recovered sequences. On the basis of EST-SSR analysis and keeping in view the purity and stability, the D. officinale germplasm resources from Jiangxi was recommended for hybridization in order to develop superior cultivars. [ABSTRACT FROM AUTHOR]

Objectives: To identify drought stress-responsive conserved microRNA (miRNA) from Dongxiang wild rice ( Oryza rufipogon Griff., DXWR) on a genome-wide scale, high-throughput sequencing technology was used to sequence libraries of DXWR samples, treated with and without drought stress. Results: 505 conserved miRNAs corresponding to 215 families were identified. 17 were significantly down-regulated and 16 were up-regulated under drought stress. Stem-loop qRT-PCR revealed the same expression patterns as high-throughput sequencing, suggesting the accuracy of the sequencing result was high. Potential target genes of the drought-responsive miRNA were predicted to be involved in diverse biological processes. Furthermore, 16 miRNA families were first identified to be involved in drought stress response from plants. Conclusion: These results present a comprehensive view of the conserved miRNA and their expression patterns under drought stress for DXWR, which will provide valuable information and sequence resources for future basis studies. [ABSTRACT FROM AUTHOR]

The article presents a research related to identification of a mutant for number of grains per panicle (NGP) in rice yield. Topics discussed include a decreased NGP trait with decreased panicle length and plant height identified for ngp4c mutant of wild-type parent, use of map-based cloning strategy for isolating the NGP4c(t) gene, and prediction of putative open reading frames (ORFs) between the fine-mapped regions.

Drought stress is severely damaging during seedling stage of rice ( Oryza sativa L.), which can lead to significant yield reductions. Dongxiang common wild rice ( Oryza rufipogon Griff., hereafter referred to as DXWR), with strong drought resistance, could be a favorable genetic resource to improve the drought resistance of cultivated rice. Xieqingzao B ( O. sativa L. ssp. indica, hereafter referred to as XB) is a representative maintainer line in hybrid rice breeding system in China. By using DXWR as donor parent, XB as recurrent parent, through continuous selfing, backcrossing and strict drought-resistant screening, we developed a strong and stable drought-resistant introgression line IL395 (BCF), whose ability of drought resistance was significantly increased than that of the recurrent parent XB at the seedling stage. Meanwhile, no significant differences existed among other major agronomic traits under normal condition, except for plant height. Physiological assessment revealed that IL395 exhibited a significant increase in levels of free proline and soluble sugars, which was associated with drought resistance. Whole genome marker analyses identified genomic segments of DXWR linking with RM171 and RM590 (chr. 10) and RM235 (chr. 12) that require further analysis as possible sources of drought resistance trait. These results suggest that DXWR could be a favorable genetic resource to improve the drought resistance of cultivated rice, and the IL395 might be a useful resource for excavating the drought-resistant genes from DXWR. [ABSTRACT FROM AUTHOR]

Activated carbon was prepared from the sewage sludge of municipal wastewater treatment plant by chemical activation (activation reagent is ZnCl2) and was used for the adsorption of dye (reactive brilliant red K-2BP). The impact of adsorbent amount, adsorption time and pH value on adsorption effect, the adsorption kinetics, and the adsorption thermodynamics were discussed according to batch adsorption tests. The results indicated that the activated carbon developed from sewage sludge (ACSS), which was mesoporous, possessed opened porous structures. The iodine number of the ACSS was 326 mg·g−1. The rate of achievement was 51.31%. The BET surface area was 298 m2·g−1 and the contents of heavy metals in the leachate didn’t exceed the contents limit. The adsorption kinetics of reactive brilliant red K-2BP on the ACSS was accorded with the two-step kinetics rate equation and pseudo-second-order kinetics equation. Compared to the Freundlich isotherm equation, the Langmuir isotherm equation showed better applicability for the adsorption. The adsorption which was favorable was an endothermic (enthalpy Δ H > 0) and spontaneous (free energy Δ G < 0) process and was accompanied by an increase in entropy (Δ S > 0). [ABSTRACT FROM AUTHOR]