Análise do transcriptoma de Fusarium decemcellulare agente causal do superbrotamento em guaranazeiro (Paullinia cupana var. sorbilis)

Abstract

Guarana from Amazonia is much appreciated for its medicinal and energizing properties, and the Amazonas state is the second national contribution in production. However, this production has been affected by a major disease of culture: the overbudding, whose causal agent is the fungus Fusarium decemcellulare. The symptoms of the disease are overbudding, hyperplasia and hypertrophy floral and stem galls. In other studies, the development of symptoms similar to those overbudding’s symptoms is associated to production, or modulation, of auxin hormone by the pathogen. Thus, this study aimed identify genes from biosynthesis pathways of auxin hormone in Fusarium decemcellulare and analyze differences between transcriptomic profiles of homothallic and heterothallic individuals. Twelve libraries were sequenced referring to six biological replicates (three homothallic individuals and three heterothallic individuals) for each growth condition: BD and MS media. Quality control of reads was carried out by Trimmomatic-0.33, FastQC and SortMeRNA softwares. Mapping reads to reference genome was done with TopHat2 software and the transcriptome assembly in each condition, as well as differential expression, were performed using the Cufflinks package (Cufflinks, Cuffmerge and Cuffdiff). Functional annotation of transcripts was performed by KEGG Automatic Annotation Server (KAAS) and Blast2GO. To verify the ability to synthesize auxin, FDC200 and CML2241 were grown in MS medium, which was then analyzed by ultra performance liquid chromatography. Genes from two putative auxin biosynthesis pathway were identified at genomic and transcriptomic levels: the indole-acetaldehyde pathway, its deviation and the tryptamine pathway. The expression of these genes was detected in both individuals, heterothallic and homothallic. A gene from a putative aminocyclopropane (ACC) deaminase also has been identified at genomic and transcriptomic levels, which is responsible for degrading the precursor of hormone ethylene, ACC. Furthermore, the auxin hormone was detected in the MS medium, where FDC200 and CML2241 were grown, confirming biosynthesis of IAA (indole-3-acetic acid) by the fungus. Therefore, the data obtained suggest the use of auxin biosynthesis and blocking of plant ethylene production by Fusarium decemcellulare to evade the host defense system, and the symptoms of overbudding in guarana plant would be a consequence of hormonal imbalance caused by the fungus.