Goeschl, C. | bioRxiv Science

bioRxiv2021

The receptor kinase SRF3 coordinates iron-level and flagellin dependent defense and growth responses in plants

Iron is critical for host-pathogen interactions. While pathogens seek to scavenge iron to spread, the host aims at decreasing iron availability to reduce pathogen virulence. Thus, iron sensing and homeostasis are of particular importance to prevent host infection and part of nutritional immunity. While the link between iron homeostasis and immunity pathways is well established in plants, how iron levels are sensed and integrated with immune response pathways remain unknown. We identified a receptor kinase, SRF3 coordinating root growth, iron homeostasis and immunity pathways via regulation of callose synthase activity. These processes are modulated by iron levels and rely on SRF3 extracellular and kinase domain which tune its accumulation and partitioning at the cell surface. Mimicking bacterial elicitation with the flagellin peptide flg22 phenocopies SRF3 regulation upon low iron levels and subsequent SRF3-dependent responses. We propose that SRF3 is part of nutritional immunity responses involved in sensing external iron levels.

plant biology↗

bioRxiv2019

Identification of novel genes involved in phosphate accumulation in Lotus japonicus through Genome Wide Association mapping of root system architecture and anion content

Phosphate is a key nutrient for plants and as it is needed in high quantities. It is highly immobile in the soil and represents a major limiting factor for plant productivity. Plants have evolved different solutions to forage the soil for phosphate and to adapt to phosphate limitation ranging from a profound tuning of their root system architecture and metabolic profile to the evolution of widespread mutualistic interactions, such as those with arbuscular mycorrhizal fungi (AM symbiosis). Despite the prevalence of AM symbiosis throughout land plants, most studies aimed at identifying genes that regulate plant responses to phosphate have been conducted in species incapable of AM symbiosis, such as Arabidopsis. Here we elucidated plant responses and their genetic basis to different phosphate levels in a plant species that is widely used as a model for AM symbiosis: Lotus japonicus. Rather than focusing on a single model strain, we measured root growth and anion content in response to different levels of phosphate in a large panel of Lotus japonicus natural accessions. This allowed us not only to uncover common as well as divergent responses within this species, but also enabled Genome Wide Association Studies by which we identified new genes regulating phosphate homeostasis in Lotus. Under low phosphate conditions, we uncovered a correlation between plant biomass and the decrease of plant phosphate concentration in plant tissues, suggesting a dilution effect. Altogether our data of the genetic and phenotypic variation within a species capable of AM complements studies that have been conducted in Arabidopsis, and advances our understanding of the continuum of genotype by phosphate level interaction that exists throughout dicot plants. Author SummaryPhosphate represents a major limiting factor for plant productivity. Plants have evolved different solutions to adapt to phosphate limitation ranging from a profound tuning of their root system architecture and metabolic profile to the evolution of widespread mutualistic interactions, such as arbuscular mycorrhizal symbiosis. Here we elucidated plant responses and their genetic basis to different phosphate levels in model legume plant species, Lotus japonicus, a plant commonly used for studying arbuscular mycorhizal symbiosis. We investigated Lotus responses to phosphate levels by combining high throughput root system architecture phenotyping and nutrient measurements with a natural variation approach. We investigated relations between root phenotypic responses and nutrient accumulation and we uncovered, under low phosphate conditions, a correlation between plant biomass and the decrease of plant phosphate concentration in plant tissues, suggesting a dilution effect. By means of Genome Wide Association mapping and integration of multiple traits, we identified new genes regulating phosphate homeostasis in Lotus.

plant biology↗

bioRxiv2019

EXOCYST70A3 controls root system depth in Arabidopsis via the dynamic modulation of auxin transport

Root system architecture (RSA), the distribution of roots in soil, plays a major role in plant survival. RSA is shaped by multiple developmental processes that are largely governed by the phytohormone auxin, suggesting that auxin regulates responses of roots that are important for local adaptation. However, auxin has a central role in numerous processes and it is unclear which molecular mechanisms contribute to the variation in RSA for environmental adaptation. Using natural variation in Arabidopsis, we identify EXOCYST70A3 as a modulator of the auxin system that causes variation in RSA by acting on PIN4 protein distribution. Allelic variation and genetic perturbation of EXOCYST70A3 leads to alteration of root gravitropic responses, resulting in a different RSA depth profile and drought resistance. Overall our findings suggest that the local modulation of the pleiotropic auxin pathway can gives rise to distinct root system architectures that can be adaptive in specific environments.

plant biology↗