Evidence for horizontal gene transfer and separation of effector recognition from effector function revealed by analysis of effector genes shared between cape gooseberry‐ and tomato‐infecting formae speciales of Fusarium oxysporum

Abstract

RNA sequencing (RNAseq) reads from cape gooseberry plants (Physalis peruviana) infected with Fusarium oxysporumf. sp. physali (Foph) were mapped against the lineage-specific transcriptome of Fusarium oxysporumf. sp. lycopersici (Fol) to look for putative effector genes. Homologues of Fol SIX1(designated SIX1a and SIX1b), SIX7, SIX10, SIX12, SIX15 and Ave1were identified. The near identity of the Foph and Fol SIX7, SIX10 and SIX12genes and their intergenic regions suggest that this gene cluster may have undergone recent lateral transfer. Foph SIX1a and SIX1bwere tested for their ability to complement a SIX1 knockout mutant of Fol. This mutant shows reduced pathogenicity on susceptible tomato plants, but is able to infect otherwise resistant tomato plants carrying the I-3 gene for Fusarium wilt resistance (SIX1 corresponds to Avr3). Neither SIX1a nor SIX1b could restore full pathogenicity on susceptible tomato plants, suggesting that any role they may play in pathogenicity is likely to be specific to cape gooseberry. SIX1b, but not SIX1a, was able to restore avirulence on tomato plants carrying I-3.These findings separate the recognition of SIX1 from its role as an effector and suggest direct recognition by I-3. A hypervariable region of SIX1undergoing diversifying selection within the F. oxysporum species complex is likely to play an important role in SIX1 recognition. These findings also indicate that I-3could potentially be deployed as a transgene in cape gooseberry to protect this emerging crop from Foph.Alternatively, cape gooseberry germplasm could be explored for I-3homologues capable of providing resistance to Foph.

Soil sterilization, pathogen and antagonist concentration affect biological control of Fusarium wilt of cape gooseberry by Bacillus velezensis Bs006

“…However, yield of cape gooseberry in Colombia has decreased from 18 t.ha −1 in 2008 to 10 t.ha −1 in 2014 (Ministerio de Agricultura 2016) mostly due to Fusarium wilt disease (FW), caused by Fusarium oxysporum (Estupiñan and Ossa 2007;Rodríguez 2013) recently designated f. sp. physali (Foph) (Simbaqueba et al 2018).…”

Characterization of Pathogenic and Nonpathogenic Fusarium oxysporum Isolates Associated with Commercial Tomato Crops in the Andean Region of Colombia

“…Seedlings transplanted to pots with a sterile mixture and mock-inoculated plants with water were used as a control. (ii) Root dipping (RD), the second method, which has been described by Mes et al [54] and adapted by Rep et al [55], Gonzalez-Cendales et al, [15] and Simbaqueba et al [56], with modifications, consisted of the uprooting of the seedlings, preserving the root integrity. The roots were submerged for 15 min in a 5 × 10 6 microconidia mL −1 suspension of Fol.…”

“…Differences in the disease incidence and disease severity between treatments were tested for statistical significance with ANOVA and Kruskal-Wallis tests using the software Statistix version 8.0 with a probability value of p = 0.05. Additional plant wilting symptoms and vascular browning were recorded and used to calculate disease scores according to the following criteria (described by Rep et al [61], Gonzalez-Cendales et al [15], and Simbaqueba et al [56]): 0, healthy plant; 1, slightly swollen or bent hypocotyl; 2, one or two brown vascular bundles in the hypocotyl; 3, at least two brown vascular bundles and growth distortion; and 4, all vascular bundles brown and plant either dead or very small and wilted. Differences in the distributions of disease scores between treatments were tested for statistical significance through pairwise two-tailed Mann-Whitney tests [62].…”

Comparison of Secreted in Xylem (SIX) genes in two fusarium wilt pathogens of ornamental palms

“…lycopersici (Fol) by multiple molecular techniques, including whole genome sequencing, proteomic and reverse translational approaches (Rep et al, 2004;Houterman et al, 2007;Lievens et al, 2009;Ma et al, 2010;Schmidt et al, 2013). Interestingly, while the 14 SIX genes of Fol have been detected in other phytopathogenic FOSC, all 14 have never been detected together in another single forma specialis (Lievens et al, 2009;Meldrum et al, 2012;Fraser-Smith et al, 2014;van Dam et al, 2016;Taylor et al, 2016;Williams et al, 2016;Simbaqueba et al, 2018). The SIX genes have even been detected at very low levels in presumed nonpathogenic F. oxysporum isolated from natural ecosystems (Rocha et al, 2016) and agricultural fields (Jelinski et al, 2017;Deltour et al, 2018).…”