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bioRxiv2026

A structurally unique effector shared between Verticillium dahliae and Fusarium oxysporum is involved in cotton defoliation and virulence on other hosts

Defoliating (D) strains of the vascular wilt fungus Verticillium dahliae cause severe yield losses in cotton and olive worldwide, yet the genetic basis underlying this pathotype has remained unknown. Here, we combined comparative genomics, functional genetics, structural analysis, and phylogenomics to uncover the molecular determinant of defoliation. We identified a small, D pathotype-specific genomic region encoding two duplicated secreted effector genes. Simultaneous deletion of both gene copies abolished pathogenicity and defoliation in cotton, olive, Nicotiana benthamiana, and Arabidopsis thaliana, whereas single deletions reduced virulence and genetic complementation restored disease symptoms. Conversely, expression of the D effector in non-defoliating strains was sufficient to induce defoliation. Moreover, or exogenous application of the purified protein, induced wilting and defoliation as well. Structural analyses revealed that D homologs share a conserved but previously uncharacterized protein fold and are distributed across Verticillium and Fusarium species, exhibiting functional diversification and host-specific activity. Phylogenomic and genomic context analyses indicate repeated horizontal transfer events mediated by giant transposable elements known as Starships. Together, our findings identify the D effector as a central pathogenicity factor that drives defoliation and virulence, and demonstrate how Starship-mediated horizontal gene transfer shapes the emergence and dissemination of an agriculturally devastating fungal trait.

plant biology↗

bioRxiv2019

Defining the root endosphere and rhizosphere microbiomes from the World Olive Germplasm Collection

Up to date, the bacterial and fungal microbial communities from the olive (Olea europaea L.) root systems have not been simultaneously studied. In this work, we show that microbial communities from the olive root endosphere are less diverse than those from the rhizosphere. But more relevant was to unveil that olive belowground communities are mainly shaped by the genotype of the cultivar when growing under the same environmental, pedological and agronomic conditions. Furthermore, Actinophytocola, Streptomyces and Pseudonocardia are the most abundant bacterial genera in the olive root endosphere, Actinophytocola being the most prevalent genus by far. In contrast, Gp6, Gp4, Rhizobium and Sphingomonas are the main genera in the olive rhizosphere. Canalisporium, Aspergillus, Minimelanolocus and Macrophomina are the main fungal genera present in the olive root system. Interestingly enough, a high proportion of so far unclassified fungal sequences at class level were detected in the rhizosphere. From the belowground microbial profiles here reported, it can be concluded that the genus Actinophytocola may play an important role in olive adaptation to environmental stresses. Moreover, the huge unknown fungal diversity suggests that there are still some fungi with important ecological and biotechnological implications that have yet to be discovered.

microbiology↗