Biology subjects

Fabro, G.

Publications and source records attributed to Fabro, G..

3 recordsLinked to original sources

bioRxiv2025

An oomycete effector that induces shade avoidance like growth and suppresses plant defenses targets the AUX/IAA protein IAA11

Filamentous pathogens, such as oomycetes, employ multiple strategies to suppress plant immunity, one of which involves manipulating phytohormone signaling pathways. The effector HaRxL106 from Hyaloperonospora arabidopsidis (Hpa), known to induce shade avoidance syndrome (SAS)-like growth, has previously been shown to interact with brassinosteroid signaling components. Here, we investigate the role of HaRxL106 in altering auxin signaling, revealing that HaRxL106 targets the AUX/IAA protein IAA11, a key negative regulator of auxin responses. Our data suggest that HaRxL106 impedes the repressive function of IAA11, enhancing auxin signaling and promoting SAS, which concurrently suppresses plant immune responses. These findings provide insights into how pathogen effectors manipulate plant growth and immunity to facilitate infection.

plant biology↗

bioRxiv2024

Downy mildew effector HaRxL106 interacts with the transcription factor BIM1 altering plant growth, BR signaling and susceptibility to pathogens

Hyaloperonospora arabidopsidis (Hpa) is an oomycete pathogen that causes downy mildew disease on Arabidopsis. This obligate biotroph manipulates the homeostasis of its host plant by secreting numerous effector proteins, among which are the RxLR-effectors. Identifying the host targets of effectors and understanding how their manipulation facilitates colonization of plants is key to improve plant resistance to pathogens. Here we characterize the interaction between the RxLR effector HaRxL106 and BIM1, an Arabidopsis transcription factor (TF) involved in Brassinosteroid (BR) signaling. We report that HaRxL106 interacts with BIM1 in vitro and in planta. BIM1 is required by the effector to increase the host plant susceptibility to (hemi)biotrophic pathogens, and thus can be regarded as a susceptibility factor. Mechanistically, HaRxL106 requires BIM1 to induce the transcriptional activation of BR-responsive genes and cause alterations in plant growth patterns that phenocopy the shade avoidance syndrome. Our results support previous observations of antagonistic interactions between activation of BR signaling and suppression of plant immune responses and reveal that BIM1, a new player in this crosstalk, is manipulated by the pathogenic effector HaRxL106. SIGNIFICANCE STATEMENTOur study reveals that the Arabidopsis transcription factor BIM1 plays a key role as a susceptibility factor that is manipulated by the oomycete effector HaRxL106 to induce the Brassinosteroid (BR) signaling pathway and suppress plant immunity. HaRxL106 induces BIM1-dependent expression of BR-responsive genes which affects normal plant growth generating a shade avoidance-like syndrome that impacts negatively on plant defenses against bacterial and oomycete pathogens.

plant biology↗

bioRxiv2017

An Oomycete Effector Protein Induces Shade Avoidance In Arabidopsis And Attenuates Salicylate Signaling By Binding To Host Proteins Of The RADICAL-INDUCED CELL DEATH1 Family

The oomycete pathogen Hyaloperonospora arabidopsidis (Hpa) causes downy mildew disease on Arabidopsis. During infection, Hpa like other biotrophic pathogens, suppresses activation of plant innate immunity by translocating effector proteins into host cells. Some of these effectors localize to the host cell nucleus where they may manipulate transcriptional reprogramming of plant defense genes. Here we report that the nuclear-localized Hpa effector HaRxL106, when expressed in Arabidopsis, induces shade avoidance and attenuates the transcriptional response to the defense signaling molecule salicylic acid. HaRxL106 interacts with RADICAL-INDUCED CELL DEATH1 (RCD1) and loss of RCD1 function renders Arabidopsis resilient against HaRxL106-mediated suppression of immunity. To further characterize the molecular functions of RCD1 we solved a crystal structure of RCD1s Poly-(ADP-ribose)-Polymerase (PARP) domain and, based on non-conservation of amino acids constituting the active site of canonical PARPs, conclude that RCD1 has no PARP activity. We report that RCD1-type proteins are phosphorylated and identified histone-modifying Mut9-like kinases (MLKs) as RCD1-interacting proteins. A mlk1,3,4 triple mutant exhibits stronger SA-induced defense marker gene expression compared to wild-type plants. Our data suggest that HaRxL106 suppresses Arabidopsis innate immunity by manipulating the function(s) of RCD1 in the host cell nucleus and point towards a role of RCD1 as a transcriptional co-regulator that integrates signals from light and pathogen sensors.

plant biology↗