Identification of genes associated with asexual reproduction in Phyllosticta citricarpa mutants obtained through Agrobacterium tumefaciens transformation

Abstract

Phyllosticta citricarpa is the epidemiological agent of Citrus Black Spot (CBS) disease, which is responsible for large economic losses worldwide. CBS is characterized by the presence of spores (pycnidiospores) in dark lesions of fruit, which are also responsible for short distance dispersal of the disease. The identification of genes involved in asexual reproduction of P. citricarpa can be an alternative for directional disease control. We analyzed a library of mutants obtained through Agrobacterium tumefaciens transformation system, looking for alterations in growth and reproductive structure formation. Two mutant strains were found to have lost the ability to form pycnidia. The flanking T-DNA insertion regions were identified on P. citricarpa genome by using blast analysis and further gene prediction. The predicted genes containing the T-DNA insertions were identified as Spindle Poison Sensitivity Scp3, Ion Transport protein, and Cullin Binding proteins. The Ion Transport and Cullin Binding proteins are known to be correlated with sexual and asexual reproduction in fungi; however, the exact mechanism by which these proteins act on spore formation in P. citricarpa needs to be better characterized. The Scp3 proteins are suggested here for the first time as being associated with asexual reproduction in fungus. This protein is associated with microtubule formation, and as microtubules play an essential role as spindle machinery for chromosome segregation and cytokinesis, insertions in this gene can lead to abnormal formations, such as that observed here in P. citricarpa. We suggest these genes as new targets for fungicide development and CBS disease control, by iRNA.

Genomic Sequencing of Phyllosticta citriasiana Provides Insight Into Its Conservation and Diversification With Two Closely Related Phyllosticta Species Associated With Citrus

“…When compared with other species in the Dothideomycetes, P. citriasiana appears to contain a less extensive set of CAZymes, for example, Alternaria alternata has 373 CAZymes while Zymoseptoria tritici contains 324 ones (Goodwin et al, 2011;Ohm et al, 2012;. It has been reported that Phyllosticta species have a relatively long time to infect citrus fruits and the scab expanded slowly in the fruit peels (Wang et al, 2012;Goulin et al, 2016), however, it is still unclear whether this phenomenon is related to the smaller number of CAZymes in these species. Pathogens can secrete a series of proteins that are deployed to the host-pathogen interface during infection, and secretome proteins play an important role in pathogenicity (Presti et al, 2015).…”

Genomic sequencing ofPhyllosticta citriasianaprovide insight into its conservation and diversification with closely relatedPhyllostictaspecies associated with citrus

“…When compared with other species in the Dothideomycetes, P. citriasiana appears to contain a much less extensive set of CAZymes, for example, Alternaria alternata has 373 CAZymes while Zymoseptoria tritici contains 324 ones (Goodwin et al, 2011; Ohm et al, 2012; Wang et al, 2016a). The smaller number of CAZymes in Phyllosticta coincides with the phenomenon that these species have a relatively long time to infect citrus fruits and the scab expanded slowly in the fruit peels (Wang et al, 2012; Goulin et al, 2016).…”

Secondary metabolites produced by the citrus phytopathogen Phyllosticta citricarpa

“…2d). The epidemiological and infection processes of CBS were explored in various studies [2,13]. It was suggested that the production of pycnidia in fruits is related to the disease symptoms, however the impact of phytotoxins in the disease development, to date, has not been addressed.…”