Laccase Directed Lignification Is One of the Major Processes Associated With the Defense Response Against Pythium ultimum Infection in Apple Roots

The CsmiR397a-CsLAC17 module regulates lignin biosynthesis to balance the tenderness and gray blight resistance in young tea shoots

Lignin accumulation can enhance the disease resistance of young tea shoots (Camellia sinensis). It also greatly reduces their tenderness, which indirectly affects the quality and yield of tea. Therefore, the regulation of lignin biosynthesis appears to be an effective way to balance tenderness and disease resistance in young tea shoots. In this study, we identified a laccase gene, CsLAC17, that is induced during tenderness reduction and gray blight infection in young tea shoots. Overexpression of CsLAC17 significantly increased the lignin content in transgenic Arabidopsis, enhancing their resistance to gray blight and decreasing stem tenderness. In addition, we found that CsLAC17 was negatively regulated by the upstream CsmiR397a by 5'-RLM-RACE, dual-luciferase assay, and transient expression in young tea shoots. Interestingly, the expression of CsmiR397a was inhibited during tenderness reduction and gray blight infection of young tea shoots. Overexpression of CsmiR397a reduced lignin accumulation, resulting in decreased resistance to gray blight and increased stem tenderness in transgenic Arabidopsis. Furthermore, the transient overexpression of CsmiR397a and CsLAC17 in tea leaves directly confirms the function of the CsmiR397a-CsLAC17 module in lignin biosynthesis and its effect on disease resistance. These results suggest that the CsmiR397a-CsLAC17 module is involved in balancing tenderness and gray blight resistance in young tea shoots by regulating lignin biosynthesis.

MdERF114 enhances the resistance of apple roots to Fusarium solani by regulating the transcription of MdPRX63

As the main fungal etiologic agent of apple (Malus domestica) replant disease (ARD), Fusarium solani seriously damages apple roots. Ethylene response factors (ERFs) play an important role in plant resistance to biotic stress. Here, we show that MdERF114 is expressed during F. solani infections and positively regulates the resistance of apple roots to F. solani. Yeast one-hybrid, dual-luciferase, electrophoretic mobility shift assays and determinations of lignin content indicated that MdERF114 directly binds the GCC-box of the MdPEROXIDASE63 (MdPRX63) promoter and activates its expression, resulting in lignin deposition in apple roots and increased resistance to F. solani. We identified a WRKY family transcription factor, MdWRKY75, that binds to the W-box of the MdERF114 promoter. Overexpression of MdWRKY75 enhanced resistance of apple roots to F. solani. MdMYB8 interacted with MdERF114 to enhance resistance to F. solani by promoting the binding of MdERF114 to the MdPRX63 promoter. In summary, our findings reveal that the MdWRKY75-MdERF114-MdMYB8-MdPRX63 module is required for apple resistance to F. solani and the application of this mechanism by Agrobacterium rhizogenes-mediated root transformation provides a promising strategy to prevent ARD.

Phosphatidylinositol-phospholipase C4 suppresses the hypersensitive response of Nicotiana benthamiana

Phospholipid signaling plays an important role in plant immune responses. Here, we isolated two phospholipase C4 (PLC4) orthologs in the Nicotiana benthamiana genome, designated as N. benthamiana PLC4-1 and PLC4-2 (NbPLC4-1 and NbPLC4-2). We created NbPLC4-1- and NbPLC4-2- silenced plants. Induction of the hypersensitive response (HR), including HR cell death and bacterial population reduction, was accelerated in both NbPLC4-1- and NbPLC4-2-silenced plants challenged with N. benthamiana-incompatible Ralstonia solanacearum 8107. The NbPLC4-1- and NbPLC4-2-silenced plants also showed enhanced expression of Nbhin1, a HR marker gene. Expressions of genes for salicylic acid (SA) and jasmonic acid (JA) signaling were drastically increased in NbPLC4-1- and NbPLC4-2-silenced plants by R. solanacearum inoculation. In addition, NbPLC4-1 and NbPLC4-2 silencing triggered reactive oxygen species (ROS) hyper-production. These results suggest that NbPLC4s are closely associated with JA, SA, and ROS signaling and act as negative regulators of the HR in N. benthamiana.

Characterization of plant laccase genes and their functions

Laccase is a copper-containing polyphenol oxidase found in different organisms. The multigene family that encodes laccases is widely distributed in plant genomes. Plant laccases oxidize monolignols to produce lignin which is important for plant growth and stress responses. Industrial applications of fungal and bacterial laccases are extensively explored and addressed. Recently many studies have focused on the significance of plant laccase, particularly in crop yield, and its functions in different environmental conditions. This review summarizes the transcriptional and posttranscriptional regulation of plant laccase genes and their functions in plant growth and development. It especially describes the responses of laccase genes to various stresses and their contributions to plant biotic and abiotic stress resistance. In-depth explanations and scientific advances will serve as foundations for research into plant laccase genes' function, mechanism, and possible applications.

Identification of Competing Endogenous RNAs (ceRNAs) Network Associated with Drought Tolerance in Medicago truncatula with Rhizobium Symbiosis

Drought, bringing the risks of agricultural production losses, is becoming a globally environmental stress. Previous results suggested that legumes with nodules exhibited superior drought tolerance compared with the non-nodule group. To investigate the molecular mechanism of rhizobium symbiosis impacting drought tolerance, transcriptome and sRNAome sequencing were performed to identify the potential mRNA-miRNA-ncRNA dynamic network. Our results revealed that seedlings with active nodules exhibited enhanced drought tolerance by reserving energy, synthesizing N-glycans, and medicating systemic acquired resistance due to the early effects of symbiotic nitrogen fixation (SNF) triggered in contrast to the drought susceptible with inactive nodules. The improved drought tolerance might be involved in the decreased expression levels of miRNA such as mtr_miR169l-5p, mtr_miR398b, and mtr_miR398c and its target genes in seedlings with active nodules. Based on the negative expression pattern between miRNA and its target genes, we constructed an mRNA-miR169l-ncRNA ceRNA network. During severe drought stress, the lncRNA alternative splicings TCONS_00049507 and TCONS_00049510 competitively interacted with mtr_miR169l-5p, which upregulated the expression of NUCLEAR FACTOR-Y (NF-Y) transcription factor subfamily NF-YA genes MtNF-YA2 and MtNF-YA3 to regulate their downstream drought-response genes. Our results emphasized the importance of SNF plants affecting drought tolerance. In conclusion, our work provides insight into ceRNA involvement in rhizobium symbiosis contributing to drought tolerance and provides molecular evidence for future study.

The composition, biotic network, and assembly of plastisphere protistan taxonomic and functional communities in plastic-mulching croplands

The increasing use of plastic film mulching has caused the accumulation of plastic film residue in soil. To date, most researches on the plastisphere have focused on bacterial and fungal communities, with few on protistan community, especially in terrestrial ecosystems. To understand plastisphere protistan communities, we collected plastic film residues from plastic-mulching croplands. The plastisphere significantly altered the alpha-diversity, structure, and composition of taxonomic and functional (consumers, phototrophs, and parasites) communities. In both the plastisphere and surrounding soil, although some consumers dominated the protistan community network, while their performance was weakened by mulch application. The ecological networks of the plastisphere community presented higher modularity, less complexity, and a lower proportion of positive connections than the networks of surrounding soil. In addition, the enriched plant pathogens (e.g., Spongospora) and keystone taxa classified as plant pathogens (e.g., Pythium) in the plastisphere imply that plastic film residues may pose a risk to soil health and plant performance. Neutral-based processes dominated the assembly of the plastisphere protistan communities, whereas niche-based processes governed the protistan community assembly of surrounding soil. This study reveals that plastic film residues generate a unique niche for protistan colonization, which disturbs protistan communities and threatens agricultural ecosystem health and function.