Comparative Transcriptome and iTRAQ Proteome Analyses of Citrus Root Responses to Candidatus Liberibacter asiaticus Infection

Abstract

Root samples of ‘Sanhu’ red tangerine trees infected with and without Candidatus Liberibacter asiaticus (CLas) were collected at 50 days post inoculation and subjected to RNA-sequencing and isobaric tags for relative and absolute quantification (iTRAQ) to profile the differentially expressed genes (DEGs) and proteins (DEPs), respectively. Quantitative real-time PCR was subsequently used to confirm the expression of 16 selected DEGs. Results showed that a total of 3956 genes and 78 proteins were differentially regulated by HLB-infection. Among the most highly up-regulated DEPs were sperm specific protein 411, copper ion binding protein, germin-like proteins, subtilisin-like proteins and serine carboxypeptidase-like 40 proteins whose transcript levels were concomitantly up-regulated as shown by RNA-seq data. Comparison between our results and those of the previously reported showed that known HLB-modulated biological pathways including cell-wall modification, protease-involved protein degradation, carbohydrate metabolism, hormone synthesis and signaling, transcription activities, and stress responses were similarly regulated by HLB infection but different or root-specific changes did exist. The root unique changes included the down-regulation in genes of ubiquitin-dependent protein degradation pathway, secondary metabolism, cytochrome P450s, UDP-glucosyl transferases and pentatricopeptide repeat containing proteins. Notably, nutrient absorption was impaired by HLB-infection as the expression of the genes involved in Fe, Zn, N and P adsorption and transportation were significantly changed. HLB-infection induced some cellular defense responses but simultaneously reduced the biosynthesis of the three major classes of secondary metabolites, many of which are known to have anti-pathogen activities. Genes involved in callose deposition were up-regulated whereas those involved in callose degradation were also up-regulated, indicating that the sieve tube elements in roots were hanging on the balance of life and death at this stage. In addition, signs of carbohydrate starvation were already eminent in roots at this stage. Other interesting genes and pathways that were changed by HLB-infection were also discussed based on our findings.

The influence of bacteria on multitrophic interactions among plants, psyllids, and pathogen

“…Many of these metabolites play a crucial role on plant metabolic processes. Several transcriptomic, proteomic and metabolomic studies revealed an important reprograming of citrus trees following CLas or CLam infection (Kim et al ., ; Aritua et al ., ; Mafra et al ., ; Nwugo et al ., ; Vyas et al ., ; Xu et al ., ; Zhong et al ., , ). These studies found changes in amino acids, sugars and other metabolites including bitter compounds such as limonin (Cevallos‐Cevallos et al ., ; Kim et al ., ; Baldwin et al ., ; Rosales & Burns, ; Slisz et al ., ; Chin et al ., ).…”

Up‐regulation of PR1 and less disruption of hormone and sucrose metabolism in roots is associated with lower susceptibility to ‘Candidatus Liberibacter asiaticus’

“…Zhong et al . () reported the carbohydrate metabolism and hormone synthesis signalling genes in roots are altered as early as 50 days post‐inoculation. However, an extensive analysis of carbohydrate status in relation to stress‐related gene expression at the early stage of Las infection of roots is still lacking.…”

Efecto del HLB sobre el rendimiento de limón mexicano en Colima, México

“…Moreover, studies at the genomic level have been ascertained that HLB can alter the expression of a large number of genes in various organs of infected plants (Kim et al, 2009;Liao and Burns, 2012;Mafra et al, 2013;Zheng and Zhao, 2013;Aritua et al, 2013;Zhong et al, 2015;Wang et al, 2016). Some genes are overexpressed, but others reduce its expression.…”

“…Some genes are overexpressed, but others reduce its expression. Genes whose expression is altered are mainly related to the plant's defense systems (Kim et al, 2009;Rawat et al, 2015;Wang et al, 2016), the sucrose and starch metabolism (Xu et al, 2015;Rawat et al, 2015;Wang et al, 2016), synthesis and signaling hormones (Martinelli et al, 2012), nutrients absorption and transport (Zhang et al, 2015;Rawat et al, 2015;Zhong et al, 2015). Mafra et al, 2013;Zheng y Zhao, 2013;Aritua et al, 2013;Zhong et al, 2015;Wang, et al, 2016).…”

“…Algunos genes son sobre expresados, pero otros reducen su expresión. Los genes cuya expresión es alterada están relacionados principalmente con sistemas de defensa de la planta (Kim et al, 2009;Rawat et al, 2015;Wang et al, 2016), el metabolismo de sacarosa y almidón, (Xu et al, 2015;Rawat et al, 2015;Wang et al, 2016), síntesis de hormonas y de señalización (Martinelli et al, 2012), absorción y transporte de nutrientes (Zhang et al, 2015;Rawat et al, 2015;Zhong et al, 2015 (Trujillo, 2010). Ese mismo año también se encontró en los estados de Quintana Roo, Nayarit y Jalisco en árboles de limón mexicano y limón persa (C. latifolia Tanaka).…”