Transcriptional responses of strawberry to Fusarium oxysporum f. sp. fragariae

Authors: JENNER, BRADLEY - University Of California; GORDON, THOMAS - University Of California; Henry, Peter

Submitted to: Meeting Abstract
Publication Type: Other
Publication Acceptance Date: 10/17/2019
Publication Date: 10/17/2019
Citation: Jenner, B.N., Gordon, T.R., Henry, P.M. 2019. Transcriptional responses of strawberry to Fusarium oxysporum f. sp. fragariae. Northern California Computational Biology Symposium, October 12, 2019, Davis, California.

Interpretive Summary: Fusarium oxysporum is a fungus that causes lethal disease in at least 106 plant species. The type of this fungus that causes disease in strawberry is diverse. Some strains cause yellowing of the leaves and are very aggressive. Other strains, which do not cause yellowing of the leaves, cause less severe disease. We sequenced RNA from strawberry plants infected with isolates that cause leaf yellowing and those that do not. RNA sequencing can reveal cellular responses in the strawberry plant to this fungus. We observed that a hormone pathway implicated in plant defense was activated in plants inoculated with isolates that cause leaf yellowing. Activation of this hormone pathway in a model plant species causes leaf yellowing as well. This pattern suggests that production of this hormone, and the cellular signaling that results, may in part explain the yellowing observed in leaves.

Technical Abstract: The Fusarium oxysporum species complex contains diverse isolates that are capable of causing disease on a wide array of plant hosts. Isolates of Fusarium oxysporum f.sp. fragariae (Fof), the cause of Fusarium Wilt of Strawberry, can induce two distinct disease phenotypes. The “yellows” phenotype is characterized by extensive chlorosis, hypervirulence and wilting, whereas the “wilt” phenotype only includes wilting. To understand the genetic and molecular mechanisms contributing to these symptomatic differences, an RNA-sequencing study was conducted on strawberry roots (cv. Camarosa) during infection. Total RNA was collected from the roots at 6- and 13-days post inoculation with three isolates of "yellows" type Fof, one isolate of "wilt" type Fof, one isolate of Fusarium oxysporum able to cause disease on blackberry, and an uninoculated control treatment. Differential expression and functional analysis was conducted with edgeR, limma, and topGO. Jasmonic acid (JA) biosynthetic and signaling genes were significantly upregulated in ‘Camarosa’ roots infected with "yellows" type isolates, in comparison with either the "wilt" isolate or control plants at 6- and 13-days post inoculation. Curiously, differential expression of several key defense response regulators downstream of JA activation was not observed in the "yellows" type isolates. Furthermore, JA pathway activation has been linked to a chlorosis phenotype in the model Fusarium oxysporum–Arabidopsis thaliana pathosystem. These transcriptional patterns suggest that fungal-induced alterations of JA-mediated signaling pathways may be contributing to the phenotypic differences observed between "yellows" and "wilt" type infections.