Abstract
Arbuscular mycorrhizal fungi (AMF) enhance plant disease resistance, while the underlying mechanisms in the molecular levels are not yet known. In this study, five-leaf-old trifoliate orange seedlings were inoculated with Funneliformis mosseae for 14 weeks and subsequently were infected by a citrus root rot pathogen Phytophthora parasitica by 7 days. The transcriptome results by Illumina HiSeq 4000 revealed that the percentage of Q30 bases reached 92.99% or above, and 29696 unigenes were annotated in a total of 63531 unigenes. 654 and 103 differentially expressed genes (DEGs) were respectively annotated in AMF-inoculated versus non-AMF-inoculated plants under non-infection and infection with P. parasitica, respectively, whilst these DEGs were related to defense mechanisms, signal transduction mechanisms and secondary metabolites biosynthesis. Forty-two genes were functionally annotated as the putative 'defense mechanism', whilst AMF inoculation induced 1 gene down-regulated and 3 genes up-regulated under P. parasitica infection. AMF inoculation stimulated more genes linked to signal transduction mechanism down-regulated than non-AMF plants. Eight genes were involved in secondary metabolites biosynthesis in AMF versus non-AMF seedlings under P. parasitica-infection conditions. Such transcriptome database provided total information in the molecular levels regarding mycorrhizal roles in tolerating Phytophthora parasitica infection.
Highlights
Citrus trees are susceptible to a large number of diseases, including root rot
Lambais and Mehdy (2010) screened out chitinase- and β-1,3-glucanase-related differentially expressed genes (DEGs) from the transcripts of Phaseolus vulgaris inoculated with Rhizophagus irregularis
Ward and Weber (2012) used RNA-Seq technology to sequence the resistant strains of raspberry ‘Latham’ infected by root rot pathogen (Phytophthora rubi), and found that pathogenesis-related protein genes, as well as genes related to tricarboxylic acid cycle and lignin synthesis pathway all presented up-regulation
Summary
Citrus trees are susceptible to a large number of diseases, including root rot. The main pathogen of citrus root rot in China is Phytophthora parasitica (Tian et al, 2018). Soil arbuscular mycorrhizal fungi (AMF) can build mutual symbionts with most plants (including citrus), viz. Arbuscular mycorrhizas (AMs) (He et al, 2019, 2020; Wu et al, 2019; Zhang et al, 2020). Many studies showed a crucial function of AMF on increased plant disease resistance (Xie et al, 2019; Zhang et al, 2019; Gao et al, 2020). Received in revised form: 15 May 2020.
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