Legumes and many nonleguminous plants enter symbiotic interactions with microbes, and it is poorly understood how host plants respond to promote beneficial, symbiotic microbial interactions while suppressing those that are deleterious or pathogenic. Trans-acting siRNAs (tasiRNAs) negatively regulate target transcripts and are characterized by siRNAs spaced in 21-nucleotide (nt) "phased" intervals, a pattern formed by DICER-LIKE 4 (DCL4) processing. A search for phased siRNAs (phasiRNAs) found at least 114 Medicago loci, the majority of which were defense-related NB-LRR-encoding genes. We identified three highly abundant 22-nt microRNA (miRNA) families that target conserved domains in these NB-LRRs and trigger the production of trans-acting siRNAs. High levels of small RNAs were matched to >60% of all ∼540 encoded Medicago NB-LRRs; in the potato, a model for mycorrhizal interactions, phasiRNAs were also produced from NB-LRRs. DCL2 and SGS3 transcripts were also cleaved by these 22-nt miRNAs, generating phasiRNAs, suggesting synchronization between silencing and pathogen defense pathways. In addition, a new example of apparent "two-hit" phasiRNA processing was identified. Our data reveal complex tasiRNA-based regulation of NB-LRRs that potentially evolved to facilitate symbiotic interactions and demonstrate miRNAs as master regulators of a large gene family via the targeting of highly conserved, protein-coding motifs, a new paradigm for miRNA function.

microRNAs as Master Regulators of the Plant NB-LRR Defense Gene Family via the Production of Phased, Trans-acting siRNAs

Plant genomes contain large numbers of cell surface leucine-rich repeat (LRR) and intracellular nucleotide binding (NB)-LRR immune receptors encoded by resistance (R) genes that recognize specific pathogen effectors and trigger resistance responses. The unregulated expression of NB-LRR genes can trigger autoimmunity in the absence of pathogen infection and inhibit plant growth. Despite the potential serious consequence on agricultural production, the mechanisms regulating R-gene expression are not well understood. We identified microRNA (miRNA) progenitor genes precursor transcripts, and two miRNAs [nta-miR6019 (22-nt) and nta-miR6020 (21-nt)] that guide cleavage of transcripts of the Toll and Interleukin-1 receptor-NB-LRR immune receptor N from tobacco that confers resistance to tobacco mosaic virus (TMV). We further showed that cleavage by nta-miR6019 triggers RNA-dependent RNA polymerase 6- and ribonuclease Dicer-like 4-dependent biogenesis of 21-nt secondary siRNAs “in phase” with the 22-nt miR6019 cleavage site. Furthermore, we found that processing of the 22-nt nta-miR6019 depended on an asymmetric bulge caused by mismatch in the nta-miR6019 precursor. Interestingly, coexpression of N with nta-miR6019 and nta-miR6020 resulted in attenuation of N-mediated resistance to TMV, indicating that these miRNAs have functional roles in NB-LRR regulation. Using a bioinformatics approach, we identified six additional 22-nt miRNA and two 21-nt miRNA families from three Solanaceae species—tobacco, tomato, and potato. We show that members of these miRNA families cleave transcripts of predicted functional R genes and trigger production of phased secondary 21-nt siRNAs. Our results demonstrate a conserved role for miRNAs and secondary siRNAs in NB-LRR/LRR immune receptor gene regulation and pathogen resistance in Solanaceae.

miRNA regulation of plant innate immune receptors

Fig.4. Neutralization by donor and pooled subtype C plasma. (A) Neutralization profile of plasma-derived donor (green) and recipient (blue) Env pseudotypes from transmission pair 135 by donor plasma. Virus infectivity, as a percentage of the control, is plotted along the vertical axis. The reciprocal of the plasma dilution is graphed along the horizontal axis on a log 10 scale. Each curve represents the sensitivity to neutralization of an individual Env pseudotype. (B) The distribution of neutralization sensitivity for donor (green) and recipient (blue) Env pseudotypes for five transmission pairs, with IC 50 values for donor plasma (rounded to the nearest two-digit value) plotted on the horizontal axis. The fraction of Env pseudotypes with a given IC 50 is indicated on the vertical axis. (C) Linear regression analysis of neutralization by donor (horizontal axis) and pooled (vertical axis) plasma for donor (green) and recipient (blue) Env pseudotypes (R-squared value 0.23; P value 0.00002; slope 0.31, standard error 0.07). The number of Env pseudotypes evaluated was 106 (5 donor and 7 recipient), 109 (8 donor and 3 recipient), 135 (14 donor and 5 recipient), 55 (12donor and 8 recipient), and 53 (6 donor and 3 recipient). R EPORTS

A MicroRNA as a Translational Repressor of APETALA2 in Arabidopsis Flower Development

Although humic acid has been demonstrated to improve the quality of some soil types, the long-term effects of humic acid on soil under continuous cropping peanut are not fully understood. This study aimed to investigate the continuous effects of humic acid on the physicochemical properties, microbial diversity, and enzyme activities of soil under continuous cropping peanut. In this study, a three-year consecutive experiment of cropping peanut was conducted in the North China Plain. In addition to the equal nitrogen, phosphorus, and potassium inputs, humic acid treatment was applied with inorganic fertilizers. Compared with control experiments, humic acid increased the yield and quality of continuous cropping peanut. To elucidate the mechanism of humic acid affecting the soil quality, various soil quality indicators were evaluated and compared in this study. It was found that humic acid increased soil nutrient contents, including the total soil nitrogen, total phosphorus, total potassium, available nitrogen, available phosphorus, available potassium, and organic matter contents, which exhibited the maximum effect in the third year. Meanwhile, the urease, sucrase, and phosphatase activities in the soil significantly increased after treated with humic acid, of which the maturity period increased most significantly. The same results were observed for three consecutive years. Microbial diversity varied considerably according to the high throughput sequencing analysis. Specifically, the number of bacteria decreased while that of fungi increased after humic acid treatment. The abundance of Firmicutes in bacteria, Basidiomycota, and Mortierellomycota in fungi all increased, which have been reported as being beneficial to plant growth. In contrast, the abundance of Ascomycota in fungi was reduced, and most of the related genera identified are pathogenic to plants. In conclusion, humic acid improved the yield and quality of continuous cropping peanut because of improved physicochemical properties, enzymatic activities, and microbial diversity of soil, which is beneficial for alleviating the obstacles of continuous cropping peanut.

/pdf/humic-acid-fertilizer-improved-soil-properties-and-soil-47c0rway13.pdf

Humic Acid Fertilizer Improved Soil Properties and Soil Microbial Diversity of Continuous Cropping Peanut: A Three-Year Experiment

MicroRNAs (miRNAs) are a class of small non-coding RNAs that have recently emerged as important regulators of gene expression, mainly through cleavage and/or translation inhibition of the target mRNAs during or after transcription. miRNAs play important roles by regulating a multitude of biological processes in plants which include maintenance of genome integrity, development, metabolism, and adaptive responses towards environmental stresses. The increasing population of the world and their food demands requires focused efforts for the improvement of crop plants to ensure sustainable food production. Manipulation of mRNA transcript abundance via miRNA control provides a unique strategy for modulating differential plant gene expression and miRNAs are thus emerging as the next generation targets for genetic engineering for improvement of the agronomic properties of crops. However, a deeper understanding of its potential and the mechanisms involved will facilitate the design of suitable strategies to obtain the desirable traits with minimum trade-offs in the modified crops. In this regard, this review highlights the diverse roles of conserved and newly identified miRNAs in various food and industrial crops and recent advances made in the uses of miRNAs to improve plants of agronomically importance so as to significantly enhance crop yields and increase tolerance to various environmental stress agents of biotic - or abiotic origin.

/pdf/functional-roles-of-micrornas-in-agronomically-important-4awx3j7ywv.pdf

Functional Roles of microRNAs in Agronomically Important Plants—Potential as Targets for Crop Improvement and Protection

Peanut is one of the most important crops in the world, both for vegetative oil and as a protein source Biotechnology approaches provide promising ways to increase peanut productivity, either through improved seed quality or stress resistance These approaches require the identification of genes that control important agronomical traits, the understanding of gene regulation and metabolic pathways, as well as ways of delivering genes or small RNAs into peanut plants Because of these requirements, extensive studies have focused on peanut functional genomics and biotechnology, and have made great strides during the past decades This review summarized the advances in peanut omics and biotechnology in China

/pdf/peanut-arachis-hypogaea-l-omics-and-biotechnology-in-china-4v2fwe1qdx.pdf

Peanut ('Arachis hypogaea L.') omics and biotechnology in China

Five putative acyl carrier protein (ACP) cDNAs were isolated from developing peanut seeds by searching ESTs of a peanut immature-seed cDNA library and PCR-based cloning. Five peanut ACPs contained a strictly conserved Ser residue in the Asp-Ser-Leu (DSL) motif, which is an important characteristic of ACPs in plants and bacteria. Three AhACPs, AhACP1, AhACP4, AhACP5, were predicted to be located in chloroplast, while two AhACPs, AhACP2 and AhACP3, in mitochondria. Comparison of genomic DNA and cDNA sequences demonstrated three chloroplast ACPs (cpACPs) comprising of four exons and three introns while two mitochondrial ACPs (mtACPs) contained two exons and one intron. More than two homologs of each AhACP were expressed in developing peanut seeds. Most homologs were verified by corresponding genomic DNA sequences. Semi-quantitative RT-PCR analysis suggested AhACP1 was a seed-predominant ACP isoform. AhACP4 and AhACP5 showed same mRNA profile in different organs and during seed development. Two mtACPs expressed highly in peanut flower tissue which was distinct from three cpACPs.

Characterization of Five Putative Acyl Carrier Protein (ACP) Isoforms from Developing Seeds of Arachis hypogaea L.

Candidate genes of multisubunit (MS) and multifunctional (MF) acetyl-CoA carboxylase (ACCase) including accB1, accB2, accC, accA, accD, and MF-ACCase were isolated from peanut by sequencing a full-length cDNA library and homology-based cloning. Primary structures of peanut ACCases were highly conserved, especially biochemical function domains, compared with other higher plants and Escherichia coli. The numbers of homologs of each ACCase gene expressed in developing seed of peanut varied from two to five. Two editing sites of peanut accD were identified by comparing genomic DNA and its corresponding cDNAs. The MS-ACCase of Arachis hypogaea and Arabidopsis thaliana shared a conservative structure of gene organization. Semiquantitative reverse transcription polymerase chain reaction analysis indicated that MS-ACCase and MF-ACCase genes were expressed in all peanut tissues examined, but their mRNA expression level were quite different. In peanut seed development, accC, accA, accD, and MF-ACCase mRNAs were expressed strongly at 60 days after pegging.

Isolation and Characterization of Putative Acetyl-CoA Carboxylases in Arachis hypogaea L.

[Development of transgenic maize with anti-rough dwarf virus artificial miRNA vector and their disease resistance].

The invention provides a method for preventing and treating bemisa babaci by utilizing an RNA (Ribose Nucleic Acid) interference (RNAi) technology, belonging to the technical field of agriculture and biology. The method provided by the invention comprises the following steps of: (1) selecting a target sequence IAP (Inhibitor Of Apoptosis Protein) gene of RNAi according to a gene sequence of the bemisa babaci and designing a PCR (Polymerase Chain Reaction) amplification primer of the target sequence; (2) extracting the RNA of the bemisa babaci and carrying out transcription to obtain a cDNA (Complementary Deoxyribonucleic Acid); then carrying out PCR amplification on the cDNA and purifying to prepare a target gene; (3) inserting the target gene into an expression vector to prepare the expression vector containing the target gene; (4) and transforming the expression vector containing the target gene into a crop to obtain a transgenic crop for preventing and treating bemisa babaci; and planting the crop. The method provided by the invention has important guiding value and theoretical significance on researching the gene function of the bemisa babaci by utilizing the RNAi technology, preventing and treating the bemisa babaci by utilizing the RNAi technology, and preventing and treating the bemisa babaci by utilizing the transgenic crop.

Method for preventing and treating bemisa babaci by utilizing RNA (Ribose Nucleic Acid) interference technology

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