Biology subjects

Rouached, H.

Publications and source records attributed to Rouached, H..

8 recordsLinked to original sources

bioRxiv2025

Phosphorus Availability Modulates Flowering Time Through Subcellular Reprogramming of bGLU25 and GRP7 in Flowering Plants

The transition from vegetative to reproductive growth is vital for plant fitness and crop yield and is strongly influenced by nutrient availability. While nitrogen deficiency accelerates flowering, phosphorus (P) limitation delays it. However, the molecular basis for how P availability regulates flowering time remains unclear. Here, through genome-wide association mapping in Arabidopsis, we uncover genetic variation in {beta}-GLUCOSIDASE 25 (bGLU25) that modulates flowering under P-limited conditions. In P-sufficient environments, bGLU25 localizes to the endoplasmic reticulum. Under P limitation, however, bGLU25 translocates to the cytosol, a process mediated by P-regulated SERINE CARBOXY PEPTIDASE 50 (SCP50). In the cytosol, bGLU25 binds to JACALIN-LECTIN LIKE1 (AtJAC1), preventing the nuclear translocation of the Flowering Locus C (FLC) regulator GLYCINE-RICH RNA-BINDING PROTEIN 7 (GRP7). This cytosolic sequestration of GRP7 under P-deprivation elevates FLC expression, delaying flowering. Moreover, in the monocot rice, the homologs of bGLU25 also modulate flowering responses to P availability, indicating a conserved role for bGLU25 across flowering plants. Our findings provide a molecular framework for breeding strategies aimed at optimizing flowering time in response to P levels.

plant biology↗

bioRxiv2024

A TORC1-PHR1 signaling axis regulates phosphorus starvation and immunity signaling network in Arabidopsis

The Target of Rapamycin Complex 1 (TORC1) is a crucial eukaryotic kinase that modulates growth in response to nutrient availability. Phosphorus (P) is an essential macronutrient, and its deficiency induces extensive reprogramming of growth and defense strategies in plants. This process involves Phosphate Starvation Response 1 (PHR1), a master regulator of the Phosphate Starvation Response (PSR). In this study, we identify a novel, non-canonical role for TORC1 in regulating P starvation responses in Arabidopsis. We demonstrate that P limitation activates TORC1, leading to the stabilization of PHR1. Inhibition of TORC1 increased sensitivity to P starvation, accompanied by disruption of starvation-induced transcriptional reprogramming. Additionally, our results reveal that the TORC1-PHR1 signaling axis plays a crucial role in reprogramming the expression of genes involved in the plant immune signaling network. This regulation is critical for the symbiotic association with the endophytic fungus Piriformospora indica under P starvation. These findings underscore the significant role of the TORC1-PHR1 module in orchestrating the PSR and highlight the evolutionary adaptation of TORC1 signaling pathways in plants.

plant biology↗

bioRxiv2023

Nutrient levels control root growth responses to high ambient temperature in plants

Global warming will lead to significantly increased temperatures on earth. Plants respond to high ambient temperature with altered developmental and growth programs, termed thermomorphogenesis. Here we show that thermomorphogenesis is conserved in Arabidopsis, soybean, and rice and that it is linked to a decrease in the levels of the two macronutrients nitrogen and phosphorus. We also find that low external levels of these nutrients abolish root growth responses to high ambient temperature. We show that in Arabidopsis, this is due to the function of the transcription factor ELONGATED HYPOCOTYL 5 (HY5) and its transcriptional regulation of the transceptor NITRATE TRANSPORTER 1.1 (NRT1.1). Soybean and Rice homologs of these genes are expressed consistently with a conserved role in regulating temperature responses in a nitrogen and phosphorus level dependent manner. Overall, our data show that root thermomorphogenesis is a conserved feature in species of the two major groups of angiosperms, monocots and dicots, that it leads to a reduction of nutrient levels in the plant, and that it is dependent on sufficient environmental nutrient supply, a regulatory process mediated by the HY5-NRT1.1 module.

plant biology↗

bioRxiv2023

The transcription factor OsbZIP48 governs rice responses to zinc deficiency

Zinc deficiency is the most prevalent micronutrient disorder in rice and leads to delayed development and decreased yield. Nevertheless, despite its primary importance, how rice responds to zinc deficiency remains poorly understood. Herein, we present genetic evidence that OsbZIP48 is essential for regulating rice responses to zinc deficiency. Using the reverse genetics approach, genetic inactivation of OsbZIP48 in rice seedlings caused a hyper sensitivity to zinc deficiency, associated with a significant decrease in the root-to-shoot translocation of zinc. Consistently, OsbZIP48 was constitutively expressed in roots, slightly induced by zinc deficiency in shoots, and localized into nuclei induced by Zn deficiency. Comparative transcriptome analysis of the wild-type plants and osbzip48 mutant grown under zinc deficiency enabled the identification of OsbZIP48 target genes, including key zinc transporter genes (OsZIP4 and OsZIP8). We demonstrated that OsbZIP48 controlled the expressions of these genes by directly binding to their promoters, specifically to the zinc deficiency response element (ZDRE) motif. Collectively, we showed that the OsbZIP48 gene encodes for a transcription factor in rice, and demonstrates its critical role in the response to zinc deficiency in this crop. This knowledge is crucial for the design of rice plants that are resilient to the globally prevalent zinc limitation through zinc bio-fortification programs.

plant biology↗

bioRxiv2021

Interdependent Iron and Phosphorus Availability Controls Photosynthesis Through Retrograde Signaling

Iron deficiency hampers photosynthesis and is associated with chlorosis. We recently showed that iron deficiency-induced chlorosis depends on phosphorus availability. How plants integrate these cues to control chlorophyll accumulation is unknown. Here, we show that iron limitation downregulates photosynthesis genes in a phosphorus-dependent manner. Using transcriptomics and genome-wide association analysis, we identify two genes, a chloroplastic ascorbate transporter (PHT4;4) and a nuclear transcription factor (bZIP58), which prevent the downregulation of photosynthesis genes leading to the stay-green phenotype under iron-phosphorus deficiency. Joint limitation of these nutrients induces ascorbate accumulation by activating expression of an ascorbate biosynthesis gene, VTC4, which requires bZIP58. Exogenous ascorbate prevents iron deficiency-induced chlorosis in vtc4 mutants, but not in bzip58 or pht4;4. Our study demonstrates chloroplastic ascorbate transport is essential for preventing the downregulation of photosynthesis genes under iron-phosphorus combined deficiency. These findings uncover a molecular pathway coordinating chloroplast-nucleus communication to adapt photosynthesis to nutrient availability.

plant biology↗

bioRxiv2019

Genome-wide expression analysis identifies core components during iron starvation in hexaploid wheat

Iron is one of essential micronutrient for all organisms. Its deficiency causes a severe loss in crops yield. Nevertheless, our current understanding on major crops response to Fe deficiency remains limited. Herein, we investigated the effect of Fe deprivation at both transcriptomic and metabolic levels in hexaploid wheat. A genome-wide gene expression reprogramming was observed with a total of 5854 genes showing differential expression in roots of wheat subjected to Fe-starved medium. Subsequent, analysis revealed a predominance of strategy-II mode of Fe uptake, with induced genome bias contribution from the A and B genomes. In general, the predominance of genes encoding for nicotianamine synthase, yellow stripe like transporters, metal transporters, ABC transporters and zinc-induced facilitator-like protein was noticed. Our transcriptomic data were in agreement with the GC-MS analysis that showed an enhancement of accumulation of various metabolites such as fumarate, malonate, succinate and xylofuranose, which could be linked for enhancing Fe-mobilization. Interestingly, Fe starvation causes a significant temporal increase of glutathione-S-transferase both at transcriptional and enzymatic activity, which indicate the important role of glutathione in the response to Fe starvation in wheat roots. Taken together, our result provides new insight on wheat response to Fe starvation and lays foundation to design strategies to improve Fe nutrition in crops.

plant biology↗

bioRxiv2018

Systems approaches provide new insights into Arabidopsis thaliana root growth under mineral nutrient limitation

The molecular genetic mechanisms by which plants modulate their root growth rate (RGR) in response to nutrient deficiency are largely unknown. Using a panel of Arabidopsis thaliana natural accessions, we provide a comprehensive combinatorial analysis of RGR variation under macro- and micronutrient deficiency, namely phosphorus (P), iron (Fe), and zinc (Zn), which affect root growth in opposite directions. We found that while -P stimulates early RGR of most accessions, -Fe or -Zn reduces it. The combination of either -P-Fe or -P-Zn leads to suppression of the growth inhibition exerted by -Fe or -Zn alone. Surprisingly, Arabidopsis reference accession Columbia (Col-0) is not representative of the species under -P and -Zn. Using a genome wide association study, we identify candidate genes that control RGR under the assayed nutrient deficiency conditions. By using a network biology driven search using these candidate genes, we further identify a functional module enriched in regulation of cell cycle, DNA replication and chromatin modification that possibly underlies the suppression of root growth reduction in -P-Fe conditions. Collectively, our findings provide a framework for understanding the regulation of RGR under nutrient deficiency, and open new routes for the identification of both large effect genes and favorable allelic variations to improve root growth.

plant biology↗

bioRxiv2017

Zinc availability modulates plant growth and immune responses via AZI1

Zinc is an essential micronutrient for all living organisms and is involved in a plethora of processes including growth and development, and immunity. However, it is unknown if there is a common genetic and molecular basis underlying multiple facets of zinc function. Here we used natural variation in Arabidopsis thaliana to study the role of zinc in regulating growth. We identify allelic variation of the systemic immunity gene AZI1 as a key for determining root growth responses to low zinc conditions. We further demonstrate that this gene is important for modulating root growth depending on the zinc and defence status. Finally, we show that the interaction of the immunity signal azelaic acid and zinc level to regulate root growth is conserved in rice. This work demonstrates that there is a common genetic and molecular basis for multiple zinc dependent processes and that nutrient cues can determine the balance of plant growth and immune responses in plants.

plant biology↗