Plant-Pathogen Interaction, Circadian Rhythm, and Hormone-Related Gene Expression Provide Indicators of Phytoplasma Infection in Paulownia fortunei

Abstract

Phytoplasmas are mycoplasma-like pathogens of witches’ broom disease, and are responsible for serious yield losses of Paulownia trees worldwide. The molecular mechanisms of disease development in Paulownia are of considerable interest, but still poorly understood. Here, we have applied transcriptome sequencing technology and a de novo assembly approach to analyze gene expression profiles in Paulownia fortunei infected by phytoplasmas. Our previous researches suggested that methyl methane sulfonated (MMS) could reverse the effects of the infection. In this study, leaf samples from healthy, infected, and both infected and methyl methane sulfonate treated plants were analyzed. The results showed that the gene expression profile of P. fortunei underwent dramatic changes after Paulownia witches’ broom (PaWB) phytoplasma infection. Genes that encoded key enzymes in plant-pathogen interaction processes were significantly up-regulated in the PaWB-infected Paulownia. Genes involved in circadian rhythm and hormone-related genes were also altered in Paulownia after PaWB infection. However, after the PaWB-infected plants were treated with MMS, the expression profiles of these genes returned to the levels in the healthy controls. The data will help identify potential PaWB disease-resistance genes that could be targeted to inhibit the growth and reproduction of the pathogen and to increase plant resistance.

Comparative Transcriptomics Analysis of Phytohormone-Related Genes and Alternative Splicing Events Related to Witches’ Broom in Paulownia

“…Leaf color is related to chloroplast development, the size and number of chloroplasts, and the production of photosynthetic pigments. Fan et al [42] also found the genes which encode PIF3 involved in light signal transduction. PIF3 takes effect in the response of Paulownia in abiotic stresses and is involved in biosynthesis and signaling pathways of hormones including brassinosteroids, GA, and abscisic acid [47].…”

“…MYC2 is the positive regulation factor mediated by JA in regulating the inhibition of stem elongation and tolerance of plants to oxidative damage. In previous studies, the MYC2 which was related to plant-pathogen interactions was identified [42]. When the JA concentration is high, JAZs are degraded, leading to MYC2 being released to promote the JA regulation of plant growth.…”

Transcriptome and Small RNA Sequencing Analysis Revealed Roles of PaWB-Related miRNAs and Genes in Paulownia fortunei

“…The involvement of ARFs in response to biotic stresses was also revealed in Arabidopsis thaliana [60], Gossypium [61] and Oryza sativa Linn [62]. In addition, Fan et al [63] suggested that the concentration of Indole-3-acetic acid (IAA) in PaWB-infected plants was significantly lower than that in healthy plants, while the concentration of cytokine (CK) in PaWB-infected plants was significantly higher than that in healthy plants. Moreover, the upregulation of CK/IAA could lead to the appearance of witches' broom symptoms.…”

Long Non-Coding RNAs Responsive to Witches’ Broom Disease in Paulownia tomentosa

“…Witches' broom disease occurs in many countries and is the biggest threat to Paulownia production, causing serious economic losses [1,2]. In Paulownia, witches' broom disease has been found in saplings and big trees, and leads to malformations of branch, leaf, stem, and flower, such as witches' broom, yellowing, phloem necrosis, and phyllody, respectively [3,4].…”

“…Rifampicin treatment can make PaWB-infected Paulownia recover to normal morphology [13]. Furthermore, the rapid development of 'omics' has allowed for the investigation of the transcriptomes [3,[14][15][16][17][18], microRNAs (miRNAs), degradomes [19][20][21][22], and proteomes [4,23] of Paulownia species, and the results have revealed changes after PaWB infection at transcriptional, post-transcriptional, and translational levels.…”