Phenylpropanoid metabolism, hormone biosynthesis and signal transduction-related genes play crucial roles in the resistance of Paulownia fortunei to paulownia witches’ broom phytoplasma infection

Transcriptomic Profiling of Sugarcane White Leaf (SCWL) Canes during Maturation Phase

Sugarcane white leaf (SCWL) disease, caused by Candidatus Phytoplasma sacchari, results in the most damage to sugarcane plantations. Some SCWL canes can grow unnoticed through the maturation phase, subsequently resulting in an overall low sugar yield, or they can be used accidentally as seed canes. In this work, 12-month-old SCWL and asymptomatic canes growing in the same field were investigated. An abundance of phytoplasma in SCWL canes affected growth and sugar content as well as alterations of transcriptomic profiles corresponding to several pathways that responded to the infection. Suppression of photosynthesis, porphyrin and chlorophyll metabolism, coupled with an increase in the expression of chlorophyllase, contributed to the reduction in chlorophyll levels and photosynthesis. Blockage of sucrose transport plausibly occurred due to the expression of sugar transporters in leaves but suppression in stalks, resulting in low sugar content in canes. Increased expression of genes associated with MAPK cascades, plant hormone signaling transduction, callose plug formation, the phenylpropanoid pathway, and calcium cascades positively promoted defense mechanisms against phytoplasma colonization by an accumulation of lignin and calcium in response to plant immunity. Significant downregulation of CPK plausibly results in a reduction in antioxidant enzymes and likely facilitates pathogen invasion, while expression of sesquiterpene biosynthesis possibly attracts the insect vectors for transmission, thereby enabling the spread of phytoplasma. Moreover, downregulation of flavonoid biosynthesis potentially intensifies the symptoms of SCWL upon challenge by phytoplasma. These SCWL sugarcane transcriptomic profiles describe the first comprehensive sugarcane-phytoplasma interaction during the harvesting stage. Understanding molecular mechanisms will allow for sustainable management and the prevention of SCWL disease-a crucial benefit to the sugar industry.

Paulownia Witches' Broom Disease: A Comprehensive Review

Phytoplasmas are insect-transmitted bacterial pathogens associated with diseases in a wide range of host plants, resulting in significant economic and ecological losses. Perennial deciduous trees in the genus Paulownia are widely planted for wood harvesting and ornamental purposes. Paulownia witches' broom (PaWB) disease, associated with a 16SrI-D subgroup phytoplasma, is a destructive disease of paulownia in East Asia. The PaWB phytoplasmas are mainly transmitted by insect vectors in the Pentatomidae (stink bugs), Miridae (mirid bugs) and Cicadellidae (leafhoppers) families. Diseased trees show typical symptoms, such as branch and shoot proliferation, which together are referred to as witches' broom. The phytoplasma presence affects the physiological and anatomical structures of paulownia. Gene expression in paulownia responding to phytoplasma presence have been studied at the transcriptional, post-transcriptional, translational and post-translational levels by high throughput sequencing techniques. A PaWB pathogenic mechanism frame diagram on molecular level is summarized. Studies on the interactions among the phytoplasma, the insect vectors and the plant host, including the mechanisms underlying how paulownia effectors modify processes of gene expression, will lead to a deeper understanding of the pathogenic mechanisms and to the development of efficient control measures.

Genome-Wide Identification and Expression of the Paulownia fortunei MADS-Box Gene Family in Response to Phytoplasma Infection

Paulownia witches’ broom (PaWB), caused by phytoplasmas, is the most devastating infectious disease of Paulownia. Although a few MADS-box transcription factors have been reported to be involved in the formation of PaWB, there has been little investigation into all of the MADS-box gene family in Paulownia. The objective of this study is to identify the MADS-box gene family in Paulownia fortunei on a genome-wide scale and explore their response to PaWB infection. Bioinformatics software were used for identification, characterization, subcellular localization, phylogenetic analysis, the prediction of conserved motifs, gene structures, cis-elements, and protein-protein interaction network construction. The tissue expression profiling of PfMADS-box genes was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Transcriptome data and the protein interaction network prediction were combined to screen the genes associated with PaWB formation. We identified 89 MADS-box genes in the P. fortunei genome and categorized them into 14 subfamilies. The comprehensive analysis showed that segment duplication events had significant effects on the evolution of the PfMADS-box gene family; the motif distribution of proteins in the same subfamily are similar; development-related, phytohormone-responsive, and stress-related cis-elements were enriched in the promoter regions. The tissue expression pattern of PfMADS-box genes suggested that they underwent subfunctional differentiation. Three genes, PfMADS3, PfMADS57, and PfMADS87, might be related to the occurrence of PaWB. These results will provide a valuable resource to explore the potential functions of PfMADS-box genes and lay a solid foundation for understanding the roles of PfMADS-box genes in paulownia–phytoplasma interactions.

Combined transcriptome and metabolome analysis of Nerium indicum L. elaborates the key pathways that are activated in response to witches' broom disease

BACKGROUND

Nerium indicum Mill. is an ornamental plant that is found in parks, riversides, lakesides, and scenic areas in China and other parts of the world. Our recent survey indicated the prevalence of witches' broom disease (WBD) in Guangdong, China. To find out the possible defense strategies against WBD, we performed a MiSeq based ITS sequencing to identify the possible casual organism, then did a de novo transcriptome sequencing and metabolome profiling in the phloem and stem tip of N. indicum plants suffering from WBD compared to healthy ones.

RESULTS

The survey showed that Wengyuen county and Zengcheng district had the highest disease incidence rates. The most prevalent microbial species in the diseased tissues was Cophinforma mamane. The transcriptome sequencing resulted in the identification of 191,224 unigenes of which 142,396 could be annotated. There were 19,031 and 13,284 differentially expressed genes (DEGs) between diseased phloem (NOWP) and healthy phloem (NOHP), and diseased stem (NOWS) and healthy stem (NOHS), respectively. The DEGs were enriched in MAPK-signaling (plant), plant-pathogen interaction, plant-hormone signal transduction, phenylpropanoid and flavonoid biosynthesis, linoleic acid and α-linoleic acid metabolism pathways. Particularly, we found that N. indicum plants activated the phytohormone signaling, MAPK-signaling cascade, defense related proteins, and the biosynthesis of phenylpropanoids and flavonoids as defense responses to the pathogenic infection. The metabolome profiling identified 586 metabolites of which 386 and 324 metabolites were differentially accumulated in NOHP vs NOWP and NOHS and NOWS, respectively. The differential accumulation of metabolites related to phytohormone signaling, linoleic acid metabolism, phenylpropanoid and flavonoid biosynthesis, nicotinate and nicotinamide metabolism, and citrate cycle was observed, indicating the role of these pathways in defense responses against the pathogenic infection.

CONCLUSION

Our results showed that Guangdong province has a high incidence of WBD in most of the surveyed areas. C. mamane is suspected to be the causing pathogen of WBD in N. indicum. N. indicum initiated the MAPK-signaling cascade and phytohormone signaling, leading to the activation of pathogen-associated molecular patterns and hypersensitive response. Furthermore, N. indicum accumulated high concentrations of phenolic acids, coumarins and lignans, and flavonoids under WBD. These results provide scientific tools for the formulation of control strategies of WBD in N. indicum.

Conformational Changes in Three-Dimensional Chromatin Structure in Paulownia fortunei After Phytoplasma Infection

Higher-order chromatin structures play important roles in regulating multiple biological processes such as growth and development as well as biotic and abiotic stress response. However, little is known about three-dimensional chromatin structures in Paulownia or about whole-genome chromatin conformational changes that occur in response to Paulownia witches' broom (PaWB) disease. We used high-throughput chromosome conformation capture (Hi-C) to obtain genome-wide profiles of chromatin conformation in both healthy and phytoplasma-infected Paulownia fortunei genome. The heat map results indicated that the strongest interactions between chromosomes were in the telomeres. We confirmed that the main structural characteristics of A/B compartments, topologically associated domains, and chromatin loops were prominent in the Paulownia genome and were clearly altered in phytoplasma-infected plants. By combining chromatin immunoprecipitation sequencing, Hi-C signals, and RNA sequencing data, we inferred that the chromatin structure changed and the modification levels of three histones (H3K4me3/K9ac/K36me3) increased in phytoplasma-infected P. fortunei, which was associated with changes of transcriptional activity. We concluded that for epigenetic modifications, transcriptional activity might function in combination to shape chromatin packing in healthy and phytoplasm-infected Paulownia. Finally, 11 genes (e.g., RPN6, Sec61 subunit-α) that were commonly located at specific topologically associated domain boundaries, A/B compartment switching and specific loops, and had been associated with histone marks were identified and considered as closely related to PaWB stress. Our results provide new insights into the nexus between gene regulation and chromatin conformational alterations in nonmodel plants upon phytopathogen infection and plant disease resistance.

Integration of metabolomics and existing omics data reveals new insights into phytoplasma-induced metabolic reprogramming in host plants

Phytoplasmas are cell wall-less bacteria that induce abnormal plant growth and various diseases, causing severe economic loss. Phytoplasmas are highly dependent on nutrients imported from host cells because they have lost many genes involved in essential metabolic pathways during reductive evolution. However, metabolic crosstalk between phytoplasmas and host plants and the mechanisms of phytoplasma nutrient acquisition remain poorly understood. In this study, using metabolomics approach, sweet cherry virescence (SCV) phytoplasma-induced metabolite alterations in sweet cherry trees were investigated. A total of 676 metabolites were identified in SCV phytoplasma-infected and mock inoculated leaves, of which 187 metabolites were differentially expressed, with an overwhelming majority belonging to carbohydrates, fatty acids/lipids, amino acids, and flavonoids. Available omics data of interactions between plant and phytoplasma were also deciphered and integrated into the present study. The results demonstrated that phytoplasma infection promoted glycolysis and pentose phosphate pathway activities, which provide energy and nutrients, and facilitate biosynthesis of necessary low-molecular metabolites. Our findings indicated that phytoplasma can induce reprograming of plant metabolism to obtain nutrients for its own replication and infection. The findings from this study provide new insight into interactions of host plants and phytoplasmas from a nutrient acquisition perspective.

iTRAQ and RNA-Seq analyses revealed the effects of grafting on fruit development and ripening of oriental melon (Cucumis melo L. var. makuwa)

Rootstocks are among the primary factors that influence fruit yield and quality as well as melon development. To understand the differences in the molecular mechanisms and gene expression networks of fruit development between grafted and nongrafted plants in oriental melon, we performed a comprehensive analysis of the transcriptome and proteome dynamic gene/protein expression profiles during fruit development in oriental melon (Cucumis melo L. var. makuwa). Using pairwise comparisons between grafted and nongrafted samples by transcriptome analysis, we identified a large number of candidate genes involved in hormonal signaling pathways, transcription factors, resistance-related biosynthetic pathways and photosynthesis-related metabolic pathways. Many transcription factor-encoded genes were significantly more strongly expressed in the grafted samples, for example, AP2/ERF, C2H2, MYB, bHLH, and AUX/IAA, which are well-known participants in the regulation of developmental processes and hormonal signaling metabolism. Some differentially expressed genes (DEGs) were enriched in flavonoid biosynthesis and phenylpropanoid biosynthesis and determined plant resistance. In addition, some differentially expressed proteins (DEPs) were enriched in photosynthesis-related pathways, which could improve fruit quality and yield. Moreover, through weighted gene coexpression network analyses, we identified modules of coexpressed genes and hub genes specifically related to grafting for different fruit developmental stages. The results suggested that graft-related modules and hub genes were primarily associated with photosynthate metabolism and hormonal signaling pathways. The results obtained in this study provide a valuable resource for dissecting the role of candidate genes governing graft-related metabolism in oriental melon fruit, suggesting an interesting correlation with the effects of rootstock on fruit development.

Plant Hormones in Phytoplasma Infected Plants

Phytoplasmas are bacterial plant pathogens that need a plant host and an insect vector for their spread and survival. In plants, the physiological responses that phytoplasmas trigger result in symptom development through effects on hormonal, nutritional, and stress signaling pathways, and the interactions between these. In this review, recent advances on the involvement of plant hormones together with their known and deduced roles in plants infected with phytoplasmas are discussed. Several studies have directly, or in many cases indirectly, addressed plant hormone systems in phytoplasma-infected plants. These have provided accumulating evidence that phytoplasmas extensively affect plant hormone pathways. Phytoplasmas thus, with disturbing complex plant hormone networks, suppress plant immunity and modify plant structure, while optimizing their nutrient acquisition and facilitating their colonization of the plants, and their dissemination among plants by their insect vectors.

Gene expression analysis of bud burst process in European hazelnut (Corylus avellana L.) using RNA-Seq

The control of bud burst process depending on temperature is crucial factor in woody perennial plants to survive in unfavorable ecological conditions. Although it has important economic and agronomic values, little information is available on the molecular mechanism of the bud burst process in Corylus avellana. Here for the first time, we conducted a de novo transcriptome-based experiment using eco-dormant leaf bud tissues. Four transcriptome libraries were constructed from the leaf bud tissues and sequenced via Illumina platform. Transcriptome analysis revealed 86,394 unigenes with a mean length of 1189 nt and an N50 of 1916 nt. Among these unigenes, 63,854 (73.78%) of them were annotated by at least one database. De novo assembled transcripts were enriched in phenylpropanoid metabolism, phytohormone biosynthesis and signal transduction pathways. Analyses of phytohormone-associated genes revealed important changes during bud burst, in response to gibberellic acid, auxin, and brassinosteroids. Approximately 2163 putative transcription factors were predicted, of which the largest number of unique transcripts belonged to the MYB transcription factor family. These results contribute to a better understanding of the regulation of bud burst genes in perennial plants.

ceRNA Cross-Talk in Paulownia Witches' Broom Disease

Long noncoding RNA (lncRNA), circular RNA (circRNA), and microRNA (miRNA) are important in the regulation of life activities. However, their function is unclear in Paulownia fortunei. To identify lncRNAs, circRNAs, and miRNA, and investigate their roles in the infection progress of Paulownia witches’ broom (PaWB) disease, we performed RNA sequencing of healthy and infected P. fortunei. A total of 3126 lncRNAs, 1634 circRNAs, and 550 miRNAs were identified. Among them, 229 lncRNAs, 65 circRNAs, and 65 miRNAs were differentially expressed in a significant manner. We constructed a competing endogenous RNA (ceRNA) network, which contains 5 miRNAs, 4 circRNAs, 5 lncRNAs, and 15 mRNAs, all of which were differentially expressed between healthy and infected P. fortunei. This study provides the first catalog of candidate ceRNAs in Paulownia and gives a revealing insight into the molecular mechanism responsible for PaWB.

Comparative Proteomic Analysis of Paulownia fortunei Response to Phytoplasma Infection with Dimethyl Sulfate Treatment

Paulownia fortunei is a widely cultivated economic forest tree species that is susceptible to infection with phytoplasma, resulting in Paulownia witches' broom (PaWB) disease. Diseased P. fortunei is characterized by stunted growth, witches' broom, shortened internodes, and etiolated and smaller leaves. To understand the molecular mechanism of its pathogenesis, we applied isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatography coupled with tandem mass spectrometry approaches to study changes in the proteomes of healthy P. fortunei, PaWB-infected P. fortunei, and PaWB-infected P. fortunei treated with 15 mg·L⁻¹ or 75 mg·L⁻¹ dimethyl sulfate. We identified 2969 proteins and 104 and 32 differentially abundant proteins that were phytoplasma infection responsive and dimethyl sulfate responsive, respectively. Based on our analysis of the different proteomes, 27 PaWB-related proteins were identified. The protein-protein interactions of these 27 proteins were analyzed and classified into four groups (photosynthesis-related, energy-related, ribosome-related, and individual proteins). These PaWB-related proteins may help in developing a deeper understanding of how PaWB affects the morphological characteristics of P. fortunei and further establish the mechanisms involved in the response of P. fortunei to phytoplasma.

Quantitative proteome-level analysis of paulownia witches' broom disease with methyl methane sulfonate assistance reveals diverse metabolic changes during the infection and recovery processes

Paulownia witches' broom (PaWB) disease caused by phytoplasma is a fatal disease that leads to considerable economic losses. Although there are a few reports describing studies of PaWB pathogenesis, the molecular mechanisms underlying phytoplasma pathogenicity in Paulownia trees remain uncharacterized. In this study, after building a transcriptome database containing 67,177 sequences, we used isobaric tags for relative and absolute quantification (iTRAQ) to quantify and analyze the proteome-level changes among healthy P. fortunei (PF), PaWB-infected P. fortunei (PFI), and PaWB-infected P. fortunei treated with 20 mg L^-1 or 60 mg L^-1 methyl methane sulfonate (MMS) (PFI-20 and PFI-60, respectively). A total of 2,358 proteins were identified. We investigated the proteins profiles in PF vs. PFI (infected process) and PFI-20 vs. PFI-60 (recovered process), and further found that many of the MMS-response proteins mapped to "photosynthesis" and "ribosome" pathways. Based on our comparison scheme, 36 PaWB-related proteins were revealed. Among them, 32 proteins were classified into three functional groups: (1) carbohydrate and energy metabolism, (2) protein synthesis and degradation, and (3) stress resistance. We then investigated the PaWB-related proteins involved in the infected and recovered processes, and discovered that carbohydrate and energy metabolism was inhibited, and protein synthesis and degradation decreased, as the plant responded to PaWB. Our observations may be useful for characterizing the proteome-level changes that occur at different stages of PaWB disease. The data generated in this study may serve as a valuable resource for elucidating the pathogenesis of PaWB disease during phytoplasma infection and recovery stages.

Proteome Profiling of Paulownia Seedlings Infected with Phytoplasma

Phytoplasma is an insect-transmitted pathogen that causes witches' broom disease in many plants. Paulownia witches' broom is one of the most destructive diseases threatening Paulownia production. The molecular mechanisms associated with this disease have been investigated by transcriptome sequencing, but changes in protein abundance have not been investigated with isobaric tags for relative and absolute quantitation. Previous results have shown that methyl methane sulfonate (MMS) can help Paulownia seedlings recover from the symptoms of witches' broom and reinstate a healthy morphology. In this study, a transcriptomic-assisted proteomic technique was used to analyze the protein changes in phytoplasma-infected Paulownia tomentosa seedlings, phytoplasma-infected seedlings treated with 20 and 60 mg·L^-1 MMS, and healthy seedlings. A total of 2,051 proteins were obtained, 879 of which were found to be differentially abundant in pairwise comparisons between the sample groups. Among the differentially abundant proteins, 43 were related to Paulownia witches' broom disease and many of them were annotated to be involved in photosynthesis, expression of dwarf symptom, energy production, and cell signal pathways.

Combination of iTRAQ proteomics and RNA-seq transcriptomics reveals multiple levels of regulation in phytoplasma-infected Ziziphus jujuba Mill

Jujube witches' broom (JWB) is caused by infection with a phytoplasma. A multi-omics approach was taken during graft infection of jujube by JWB-infected scion through the analysis of the plant transcriptome, proteome and phytohormone levels. A high number of differentially expressed genes (DEGs) were identified 37 weeks after grafting (WAG), followed by observation of typical symptoms of JWB at 48 WAG. At 37 WAG, the majority of the upregulated DEGs and differentially expressed proteins (DEPs) were related to flavonoid biosynthesis, phenylalanine metabolism and phenylpropanoid biosynthesis. Two of the four upregulated proteins were similar to jasmonate-induced protein-like. Among the downregulated genes, the two most populated GO terms were plant-pathogen interaction and plant hormone signal transduction (mainly for tryptophan metabolism). Moreover, phytoplasma infection resulted in reduced auxin content and increased jasmonate content, indicating that auxin and jasmonic acid have important roles in regulating jujube responses during the first and second stages of phytoplasma infection. At 48 WAG, the two largest groups of upregulated genes were involved in phenylpropanoid biosynthesis and flavonoid biosynthesis. Both genes and proteins involved in carbon metabolism and carbon fixation in photosynthetic organisms were downregulated, indicating that photosynthesis was affected by the third stage of phytoplasma infection.

Comparative proteomics reveals that central metabolism changes are associated with resistance against Sporisorium scitamineum in sugarcane

BACKGROUND

Sugarcane smut, which is caused by Sporisorium scitamineum, has been threatening global sugarcane production. Breeding smut resistant sugarcane varieties has been proven to be the most effective method of controlling this particular disease. However, a lack of genome information of sugarcane has hindered the development of genome-assisted resistance breeding programs. Furthermore, the molecular basis of sugarcane response to S. scitamineum infection at the proteome level was incomplete and combining proteomic and transcriptional analysis has not yet been conducted.

RESULTS

We identified 273 and 341 differentially expressed proteins in sugarcane smut-resistant (Yacheng05-179) and susceptible (ROC22) genotypes at 48 h after inoculation with S. scitamineum by employing an isobaric tag for relative and absolute quantification (iTRAQ). The proteome quantitative data were then validated by multiple reaction monitoring (MRM). The integrative analysis showed that the correlations between the quantitative proteins and the corresponding genes that was obtained in our previous transcriptome study were poor, which were 0.1502 and 0.2466 in Yacheng05-179 and ROC22, respectively, thereby revealing a post-transcriptional event during Yacheng05-179-S. scitamineum incompatible interaction and ROC22-S. scitamineum compatible interaction. Most differentially expressed proteins were closely related to sugarcane smut resistance such as beta-1,3-glucanase, peroxidase, pathogenesis-related protein 1 (PR1), endo-1,4-beta-xylanase, heat shock protein, and lectin. Ethylene and gibberellic acid pathways, phenylpropanoid metabolism and PRs, such as PR1, PR2, PR5 and PR14, were more active in Yacheng05-179, which suggested of their possible roles in sugarcane smut resistance. However, calcium signaling, reactive oxygen species, nitric oxide, and abscisic acid pathways in Yacheng05-179 were repressed by S. scitamineum and might not be crucial for defense against this particular pathogen.

CONCLUSIONS

These results indicated complex resistance-related events in sugarcane-S. scitamineum interaction, and provided novel insights into the molecular mechanism underlying the response of sugarcane to S. scitamineum infection.

Quantitative Proteomic and Transcriptomic Study on Autotetraploid Paulownia and Its Diploid Parent Reveal Key Metabolic Processes Associated with Paulownia Autotetraploidization

Polyploidy plays a very important role in speciation and plant evolution by way of genomic merging and doubling. In the process of polyploidy, rapid genomic, and transcriptomic changes have been observed and researched. However, proteomic divergence caused by the effects of polyploidization is still poorly understood. In the present study, we used iTRAQ coupled with mass spectrometry to quantitatively analyze proteomic changes in the leaves of autotetraploid Paulownia and its diploid parent. A total of 2963 proteins were identified and quantified. Among them, 463 differentially abundant proteins were detected between autotetraploid Paulownia and its diploid parent, and 198 proteins were found to be non-additively abundant in autotetraploid Paulownia, suggesting the presence of non-additive protein regulation during genomic merger and doubling. We also detected 1808 protein-encoding genes in previously published RNA sequencing data. We found that 59 of the genes that showed remarkable changes at mRNA level encoded proteins with consistant changes in their abundance levels, while a further 48 genes that showed noteworthy changes in their expression levels encoded proteins with opposite changes in their abundance levels. Proteins involved in posttranslational modification, protein turnover, and response to stimulus, were significantly enriched among the non-additive proteins, which may provide some of the driving power for variation and adaptation in autopolyploids. Quantitative real-time PCR analysis verified the expression patterns of related protein-coding genes. In addition, we found that the percentage of differentially abundant proteins that matched previously reported differentially expressed genes was relatively low.

Transcriptome, microRNA, and degradome analyses of the gene expression of Paulownia with phytoplamsa

BACKGROUND

Paulownia witches' broom (PaWB) is a fatal disease of Paulownia caused by a phytoplasma. In previous studies, we found that plants with PaWB symptoms would revert to a healthy morphology after methyl methane sulfonate (MMS) treatment. To completely understand the gene expression profiles of the Paulownia-phytoplasma interaction, three high-throughput sequencing technologies were used to investigate changes of gene expression and microRNAs (miRNAs) in healthy Paulownia tomentosa plantlets, PaWB-infected plantlets, and PaWB-infected plantlets treated with 60 mg · L(-1) MMS.

METHODS

Transcriptome, miRNAs and degradome sequencing were performed to explore the global gene expression profiles in the process of Paulownia tomentosa with phytoplasma infection.

RESULTS

A total of 98,714 all-unigenes, 62 conserved miRNAs, and 35 novel miRNAs were obtained, among which 902 differentially expressed genes (DEGs) and 24 miRNAs were found to be associated with PaWB disease. Subsequently, the target genes of these miRNAs were predicted by degradome sequencing. Interestingly, we found that 19 target genes of these differentially expressed miRNAs were among the 902 DEGs. The targets of pau-miR156g, pau-miR403, and pau-miR166c were significantly up-regulated in the P. tomentosa plantlets infected with phytoplasma. Interaction of miRNA -target genes mediated gene expression related to PaWB were identified.

CONCLUSIONS

The results elucidated the possible roles of the regulation of genes and miRNAs in the Paulownia-phytoplasma interaction, which will enrich our understanding of the mechanisms of PaWB disease in this plant.