Rice-Magnaporthe oryzae interactions in resistant and susceptible rice cultivars under panicle blast infection based on defense-related enzyme activities and metabolomics.

Rice blast, caused by rice blast fungus (Magnaporthe oryzae), is a global threat to food security, with up to 50% yield losses. Panicle blast is a severe form of rice blast, and disease responses vary between cultivars with different genotypes. Reactive oxygen species (ROS)-mediated signaling reactions and the phenylpropanoid pathway are important defense mechanisms involved in recognizing and resisting against fungal infection. To understand rice-M. oryzae interactions in resistant and susceptible cultivars, we determined dynamic changes in the activities of five defense-related enzymes in resistant cultivar jingsui 18 and susceptible cultivar jinyuan 899 infected with M. oryzae from 4 to 25 days after infection. We then performed untargeted metabolomics analyses to profile the metabolomes of the cultivars under infected and non-infected conditions. Dynamic changes in the activities of five defense-related enzymes were closely related to panicle blast resistance in rice. Metabolome data analysis identified 634 differentially accumulated metabolites (DAMs) between resistant and susceptible cultivars following infection, potentially explaining differences in disease response between varieties. The most enriched DAMs were associated with lipids and lipid-like molecules, phenylpropanoids and polyketides, organoheterocyclic compounds, organic acids and derivatives, and lignans, neolignans, and related compounds. Multiple metabolic pathways are involved in resistance to panicle blast in rice, including biosynthesis of other secondary metabolites, amino acid metabolism, lipid metabolism, phenylpropanoid biosynthesis, arachidonic acid metabolism, arginine biosynthesis, tyrosine metabolism, tryptophan metabolism, tyrosine and tryptophan biosynthesis, lysine biosynthesis, and oxidative phosphorylation.

Comparison of Transcriptome between Tolerant and Susceptible Rice Cultivar Reveals Positive and Negative Regulators of Response to Rhizoctonia solani in Rice.

Rice (Oryza sativa L.) is one of the world's most crucial food crops, as it currently supports more than half of the world's population. However, the presence of sheath blight (SB) caused by Rhizoctonia solani has become a significant issue for rice agriculture. This disease is responsible for causing severe yield losses each year and is a threat to global food security. The breeding of SB-resistant rice varieties requires a thorough understanding of the molecular mechanisms involved and the exploration of immune genes in rice. To this end, we conducted a screening of rice cultivars for resistance to SB and compared the transcriptome based on RNA-seq between the most tolerant and susceptible cultivars. Our study revealed significant transcriptomic differences between the tolerant cultivar ZhengDao 22 (ZD) and the most susceptible cultivar XinZhi No.1 (XZ) in response to R. solani invasion. Specifically, the tolerant cultivar showed 7066 differentially expressed genes (DEGs), while the susceptible cultivar showed only 60 DEGs. In further analysis, we observed clear differences in gene category between up- and down-regulated expression of genes (uDEGs and dDEGs) based on Gene Ontology (GO) classes in response to infection in the tolerant cultivar ZD, and then identified uDEGs related to cell surface pattern recognition receptors, the Ca2+ ion signaling pathway, and the Mitogen-Activated Protein Kinase (MAPK) cascade that play a positive role against R. solani. In addition, DEGs of the jasmonic acid and ethylene signaling pathways were mainly positively regulated, whereas DEGs of the auxin signaling pathway were mainly negatively regulated. Transcription factors were involved in the immune response as either positive or negative regulators of the response to this pathogen. Furthermore, our results showed that chloroplasts play a crucial role and that reduced photosynthetic capacity is a critical feature of this response. The results of this research have important implications for better characterization of the molecular mechanism of SB resistance and for the development of resistant cultivars through molecular breeding methods.

PacBio full-length transcriptome analysis provides new insights into transcription of chloroplast genomes.

Chloroplast and mitochondrial DNA (cpDNA and mtDNA) are apart from nuclear DNA (nuDNA) in a eukaryotic cell. The transcription system of chloroplasts differs from those of mitochondria and eukaryotes. In contrast to nuDNA and animal mtDNA, the transcription of cpDNA is still not well understood, primarily due to the unresolved identification of transcription initiation sites (TISs) and transcription termination sites (TTSs) on the genome scale. In the present study, we characterized the transcription of chloroplast (cp) genes with greater accuracy and comprehensive information using PacBio full-length transcriptome data from Arabidopsis thaliana. The major findings included the discovery of four types of artifacts, the validation and correction of cp gene annotations, the exact identification of TISs that start with G, and the discovery of polyA-like sites as TTSs. Notably, we proposed a new model to explain cp transcription initiation and termination at the whole-genome level. Four types of artifacts, degraded RNAs and splicing intermediates deserve the attention from researchers working with PacBio full-length transcriptome data, as these contaminant sequences can lead to incorrect downstream analysis. Cp transcription initiates at multiple promoters and terminates at polyA-like sites. Our study provides new insights into cp transcription and new clues to study the evolution of promoters, TISs, TTSs and polyA tails of eukaryotic genes.

Comprehensive Evaluation of Raw Eating Quality in 81 Sweet Potato (Ipomoea batatas (L.) Lam) Varieties.

The raw eating quality of sweet potato is complex. As consumers start paying more attention to the raw eating quality of tuberous roots in sweet potato, the evaluation of the raw eating quality of sweet potato is becoming an important issue. Therefore, we measured 16 quality indicators in 81 varieties of sweet potato. It was found that these 16 quality traits had different coefficients of variation (C.V.). Among them, the C.V. of fructose, glucose, and adhesiveness were the largest: 87.95%, 87.43% and 55.09%, respectively. The cluster analysis method was used to define six categories of the different tuberous roots of sweet potato. Group I, III, and IV had a stronger hardness and higher starch and cellulose content. Groups II, V, and VI were softer, with a high moisture and soluble sugar content. The principal component analysis method was used to comprehensively evaluate 16 quality indicators of 81 sweet potato varieties. It was found that Futian1, Taishu14, and Nanshu022 are good varieties in terms of raw eating quality. These varieties have low hardness, high adhesiveness in texture, high soluble sugar content, and low starch and cellulose. Future research should focus on improving the raw eating quality of sweet potato by reducing hardness, starch, and cellulose, while increasing adhesiveness, soluble sugar, and moisture content.

Rice straw enhancing catalysis of Pseudomonas fluorescens lipase for synthesis of citronellyl acetate.

Citronellyl acetate as an important flavor, can be effectively synthesized by lipase catalysis in nonaqueous system. But lipases usually behave low catalytic activity due to aggregation and denaturation of them in organic phase. To enhance the nonaqueous catalysis, based on the mechanism of lipases activated at water/oil (organic phase) interface, the inexpensive race straw was processed into powder and filaments on which Pseudomonas fluorescens lipase was immobilized by physical adsorption, used for synthesis of citronellyl acetate via transesterification of citronellol and vinyl acetate. Results showed that the desired loading was 10 mg lipase immobilized on 30 mg rice straw filaments or 25 mg rice straw powder. When the two immobilized lipases were employed in the reaction system consisted of 1-mL citronellol and 2-mL vinyl acetate at 37 â„ƒ and 160 rpm, the conversions all reached 99.8% after 12 h. Under the reaction condition, the conversion catalyzed by 10 mg native lipase was 85.1%. Undergoing six times of 8-h reuses in the organic system, the filament and power immobilized lipases had weak activity attenuation rates 0.36 and 0.32% h-1, lower than 1.52% h-1 of native lipase. Even at the room temperature and the static state without shaking and stirring, the rice straw filaments immobilized lipase could brought conversion 62.9% after 10 h but the native lipase only gave 37.0%. Obviously, the rice straw, especially its filaments, is an inexpensive and available natural material to prepare immobilized lipase with desired catalysis in organic phase, meant significant potential in flavor industry.