Transcriptome analysis of watermelon (Citrullus lanatus) fruits in response to Cucumber green mottle mosaic virus (CGMMV) infection

Abstract

Cucumber green mottle mosaic virus (CGMMV) belongs to the Tobamovirus genus and is a major global plant virus on cucurbit plants. It causes severe disease symptoms on infected watermelon plants (Citrullus lanatus), particularly inducing fruit decay. However, little is known about the molecular mechanism of CGMMV-induced watermelon fruit decay. For this study, comparative analysis of transcriptome profiles of CGMMV-inoculated and mock-inoculated watermelon fruits were conducted via RNA-Seq. A total of 1,621 differently expressed genes (DEGs) were identified in CGMMV-inoculated watermelon, among which 1,052 were up-regulated and 569 were down-regulated. Functional annotation analysis showed that several DEGs were involved in carbohydrate metabolism, hormone biosynthesis and signaling transduction, secondary metabolites biosynthesis, and plant-pathogen interactions. We furthermore found that some DEGs were related to cell wall components and photosynthesis, which may directly be involve in the development of the symptoms associated with diseased watermelons. To confirm the RNA-Seq data, 15 DEGs were selected for gene expression analysis by qRT-PCR. The results showed a strong correlation between these two sets of data. Our study identified many candidate genes for further functional studies during CGMMV-watermelon interactions, and will furthermore help to clarify the understanding of pathogenic mechanism underlying CGMMV infection in cucurbit plants.

iTRAQ-Based Proteomic Analysis of Watermelon Fruits in Response to Cucumber green mottle mosaic virus Infection

“…However, there are still no reports on proteomic profiles in response to CGMMV infection in watermelon, especially in fruits. In a previous study, we utilized HTS technology to analyze the transcriptomic changes of CGMMV-inoculated watermelon fruits [30]. In this study, we further employed the iTRAQ technique to carry out a comparative study of the proteomic profiles between CGMMV-inoculated and mock-inoculated watermelon fruits to explore the molecular mechanisms underlying "watermelon blood flesh" caused by CGMMV infection.…”

“…In our study, we found that the expression levels of CS and UGE were induced, while PK and HK3 were significantly downregulated after CGMMV infection. Significant changes in sugar contents (sucrose, glucose, and fructose) of watermelon fruits were found after CGMMV infection [47], and the genes related to pyruvate metabolism and the fermentation pathway were also strongly affected by CGMMV infection at the transcriptional level [30]. Therefore, it is speculated that CGMMV infection may influence the pyruvate metabolism and citrate cycle, and further cause a disturbance in the energy supply and sugar content in the watermelon fruits.…”

“…In a previous study, we identified 1621 differentially expressed genes (DEGs) from the transcriptome profiles of CGMMV-inoculated and mock-inoculated watermelon fruits [30]. Since the expressions of many genes are regulated at the translational levels, proteome analysis is required for deeply understanding the defense mechanism.…”

“…Comparative analysis of transcriptome profiles of CGMMV-inoculated and mock-inoculated watermelon fruits has been carried out in our previous study [30]. The transcriptome data have been deposited in NCBI Sequence Read Archive (SRA, http://www.ncbi.nlm.nih.gov/Traces/sra) with the accession numbers SRR565820-SRR565824.…”

“…Annotation analysis found that these DAPs included cytochrome complex subunit, phenylalanine-related enzymes, peroxidases, actin, histone, and other protein classes, which mainly participated in host phenylalanine metabolism, phenylpropanoid biosynthesis, and methane metabolic pathways [29]. In a previous study, we have employed high-throughput sequencing technology to analyze transcriptome differences between CGMMV-inoculated and mock-inoculated watermelon fruits [30]. In this study, we further employed iTRAQ combined with high-performance liquid chromatography tandem-mass spectrometry (HPLC-MS/MS) to explore DAPs in watermelon fruits after CGMMV infection.…”