Biology subjects

Darino, M. A.

Publications and source records attributed to Darino, M. A..

3 recordsLinked to original sources

bioRxiv2026

Methods for evaluating bacterial dispersal on hyphal networks

In heterogeneous environments, the hyphae of filamentous fungi and oomycetes can facilitate the dispersal of other microorganisms. The use of these "fungal highways" (FH) is regulated by both physical and biological factors with their interplay resulting in variable capabilities of different microbes to establish FH. Several devices have been developed to test the movement of bacteria across mycelium. However, these methods are usually time-consuming and cannot be applied either at a large scale or in a high throughput format. In this study, we developed 3D-printed experimental devices that physically separate two environments while allowing hyphal networks to act as bridges for bacterial movement. The final design allows for the simultaneous testing of up to 10 pairs and the inclusion of any culturing media. With these devices, we investigated how fungal-bacterial pairing, nutrient conditions, and inoculation strategies influence FH formation. Bacterial transport was limited in nutrient-rich media but increased under poorer nutrient conditions, consistent with enhanced exploratory growth of the mycelium. Both cis- and trans-inoculation supported FH formation, although bacterial arrival was delayed in the absence of co-inoculation. The devices were used to demonstrate that transport of bacteria by FH was relevant for the colonization of a natural substrate. Finally, we established a novel in planta assay to evaluate FH formation during host colonization. This assay demonstrated that Fusarium graminearum can transport bacteria during wheat spike colonization. Together, these results provide accessible, scalable tools to study hyphal-mediated bacterial dispersal and highlight the combined role of biological specificity and nutrient context in the establishment of FH. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=75 SRC="FIGDIR/small/719220v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1cf39aforg.highwire.dtl.DTLVardef@1d41e6corg.highwire.dtl.DTLVardef@1196637org.highwire.dtl.DTLVardef@85cc6c_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

TOPLESS promotes plant immunity by repressing auxin signaling and is targeted by the fungal effector Naked1

In plants, the antagonism between growth and defense is hardwired by hormonal signaling. Perception of Pathogen Associated Molecular Patterns (PAMPs) from invading microorganisms inhibits auxin signaling and growth. Conversely, pathogens manipulate auxin signaling to promote disease, but how this hormone inhibits immunity is not fully understood. Ustilago maydis is a maize pathogen that induces auxin signaling in its host. We characterized an U. maydis effector protein, Naked1 (Nkd1), that is translocated into the host nucleus. Through its native EAR motif, Nkd1 binds to the transcriptional co-repressors TOPLESS/TOPLESS related (TPL/TPRs) and prevents the recruitment of transcriptional repressors involved in hormonal signaling, leading to de-repression of auxin and jasmonate signaling. Moderate up-regulation of auxin signaling inhibits an early defense response, PAMP-triggered ROS burst. Thus, our findings establish a clear mechanism for auxin-induced pathogen susceptibility. Manipulation of TPL by Nkd1 is evolutionary well balanced as engineered Nkd1 variants with increased expression or increased EAR-mediated TPL/TPR binding trigger typical salicylic acid mediated defense reactions, leading to pathogen resistance.

plant biology↗

bioRxiv2019

Fungal effector Jsi1 hijacks plant JA/ET signaling through Topless

Ustilago maydis (U. maydis) is the causal agent of maize smut disease. During the colonization process, the fungus secretes effector proteins which suppress immune responses and redirect the host-metabolism in favor of the pathogen. Here we describe a novel strategy by which U. maydis induces plant jasmonate/ethylene (JA/ET) hormone signaling and thereby biotrophic susceptibility. The U. maydis effector Jasmonate/Ethylene signaling inducer 1 (Jsi1) possesses an ethylene-responsive element binding factor-associated amphiphilic repression (EAR) motif, DLNxxP, which interacts with the second WD40 domain of the conserved plant co-repressor family Topless/Topless related (TPL/TPR). Jsi1 interaction with TPL/TPRs leads to derepression of the ethylene response factor (ERF) branch of the JA/ET signaling pathway, supporting biotrophic susceptibility. Jsi1 likely activates the ERF branch by interfering with the binding of endogenous DLNxxP motif-containing ERF transcription factors to TPL/TPR proteins. The identification of effector proteins possessing a DLNxxP motif in different fungal species with biotrophic and hemibiotrophic lifestyles together with the validation of the interaction between such effectors from Magnaporthe oryzae (M. oryzae), Sporisorium scitamineum (S. scitamineum), and S. reilianum with TPL proteins indicates the convergent evolution of effectors for modulating the TPL/TPR co-repressor hub.

plant biology↗