Protein Activity of the Fusarium fujikuroi Rhodopsins CarO and OpsA and Their Relation to Fungus–Plant Interaction

Abstract

Fungi possess diverse photosensory proteins that allow them to perceive different light wavelengths and to adapt to changing light conditions in their environment. The biological and physiological roles of the green light-sensing rhodopsins in fungi are not yet resolved. The rice plant pathogen Fusarium fujikuroi exhibits two different rhodopsins, CarO and OpsA. CarO was previously characterized as a light-driven proton pump. We further analyzed the pumping behavior of CarO by patch-clamp experiments. Our data show that CarO pumping activity is strongly augmented in the presence of the plant hormone indole-3-acetic acid and in sodium acetate, in a dose-dependent manner under slightly acidic conditions. By contrast, under these and other tested conditions, the Neurospora rhodopsin (NR)-like rhodopsin OpsA did not exhibit any pump activity. Basic local alignment search tool (BLAST) searches in the genomes of ascomycetes revealed the occurrence of rhodopsin-encoding genes mainly in phyto-associated or phytopathogenic fungi, suggesting a possible correlation of the presence of rhodopsins with fungal ecology. In accordance, rice plants infected with a CarO-deficient F. fujikuroi strain showed more severe bakanae symptoms than the reference strain, indicating a potential role of the CarO rhodopsin in the regulation of plant infection by this fungus.

Fungal evolution: cellular, genomic and metabolic complexity

“…For instance, fungi are able to detect the ratio of different wavelengths of light to adjust to their surroundings, similar to phototropin‐mediated signalling in plants (Fuller, Loros & Dunlap, ; Fischer et al ., ; Schumacher, ). In many fungi, light can affect expression of genes, including those involved in important processes such as reproduction, morphogenesis, virulence and metabolism (Corrochano & Garre, ; Kamada et al ., ; Idnurm, ; Fuller et al ., ; Fischer et al ., ; Schumacher, ; Adam et al ., ; Wang et al ., ). Fungi possess well‐studied circadian clocks, too (Dunlap & Loros, , ; Liu & Bell‐Pedersen, ; Salichos & Rokas, ; Fuller et al ., ).…”

“…These are not the only light‐sensitive proteins in fungi. Opsin‐like proteins in fungi are involved in regulation of the sexual cycle and in pathogenesis in some species, including Fusarium fujikuroi (Hypocreales) (García‐Martínez et al ., ; Adam et al ., ) and Blastocladiella emersonii (Blastocladiomycota) (Scheib et al ., ). Despite the ancient nature of this protein family, information about the biological roles of its members is still very fragmented.…”

The Gibberellin Producer Fusarium fujikuroi: Methods and Technologies in the Current Toolkit

“…The infected plants were grown for another 10 days with the programmed lighting and nutrient supply. Finally, the plant length and internodal distances were recorded, while the paler pigmentation of the bakanae disease was characterized and verified by measuring their content ratio of chlorophylls/carotenoids (Adam et al, 2018). Similar to the previously described experiment, the whole assay took around 2 weeks to evaluate the systemic F. fujikuroi infection of the rice plant in vivo (see Figure 1).…”

Plant–Microbe Interaction 2017—The Good, the Bad and the Diverse

“…Adam et al analyzed a completely different aspect in the interaction of fungal pathogens with plants [ 10 ]. They found that phytopathogenic and phyto-associated ascomycetes contain rhodopsin-encoding genes.…”

“…While CarO was previously shown to be a light-driven proton pump, here the authors show that CarO is positively regulated by presence of indole-3-acetic acid and of sodium acetate. Intriguingly, they showed that deletion of the CarO-encoding gene from the genome of F. fujikuroi resulted in a hypervirulent strain with more severe bakanae symptoms than the reference strain, indicating that CarO has a role in attenuating the disease potential of the fungus [ 10 ]. Thus, although our knowledge on how plant pathogens infect host plants and on how the plants react to pathogen attack steadily increases, much remains still unknown.…”