Biology subjects

Poirier, Y.

Publications and source records attributed to Poirier, Y..

7 recordsLinked to original sources

bioRxiv2025

The EXS domain of rice PHOSPHATE1 (OsPHO1;2) reduces the low phosphate response through jasmonate signaling

Phosphorus (P) is a vital macronutrient essential for plant growth, and its deficiency significantly hampers agricultural productivity. The PHOSPHATE 1 (PHO1) protein family, characterized by an N-terminal SPX domain, four transmembrane (4TM) domains, and a C-terminal EXS domain, is pivotal in transporting phosphate (Pi) from roots to shoots. Rice, PHO1;2 plays a crucial role in the Pi export process, and defects in this gene cause severe growth retardation and Pi deficiency symptoms even when external Pi levels are adequate. This study examined the roles of the EXS domain and the combined 4TM+EXS domains of OsPHO1;2 in supporting plant growth responses, independent of Pi transport activity, as well as their influence on hormone signaling and gene regulation. Using CRISPR/Cas9, rice lines expressing specific OsPHO1;2 domains (EXS or 4TM+EXS) were created by targeted deletion of particular domain-coding regions. Phenotypic analysis under Pi-sufficient and deficient conditions, as well as phosphate profiling, revealed that EXS lines exhibited notably better growth than loss-of-function mutants, ospho1;2, during early development, despite having similar shoot Pi levels to the null mutant. These lines showed lower levels of defense hormones (jasmonic acid) than ospho1;2 but were comparable to those in the wild type. Conversely, 4TM+EXS lines exhibited growth patterns similar to ospho1;2 mutants. RNA sequencing indicated that the phosphate starvation response (PSR) and defense pathways were less pronounced in the EXS lines compared to ospho1;2 mutants. However, both EXS and 4TM+EXS lines showed seed development defects and reduced total phosphorus content in seeds, mirroring the ospho1;2 phenotype. Heterozygous plants carrying one functional OsPHO1;2 allele displayed normal growth and seed development, indicating the mutations recessive nature. The findings suggest that the EXS domain of OsPHO1;2 can promote plant growth independently of Pi transport by decreasing PSR and modulating defense hormone pathways. This further suggests a signaling role for PHO1 domains beyond direct Pi translocation. Overall, these results enhance our understanding of Pi homeostasis and may help form strategies for breeding P-efficient crops.

molecular biology↗

bioRxiv2024

DOMON domain-containing proteins control root development upon phosphate deficiency and ammonium stress by modulating iron dynamics

Phosphorous and nitrogen are the main nutrients limiting plant growth in natural and agricultural systems. Plants typically uptake phosphorous in the form of inorganic phosphate, whereas the main nitrogen sources are nitrate and ammonium. Roots show a high degree of developmental plasticity in response to nutritional stresses, directly influencing plant fitness and stress resilience. In Arabidopsis thaliana, phosphate deficiency and high levels of ammonium in the media triggers a strong inhibition of the primary root growth. This developmental response is initiated by the accumulation of apoplastic iron in specific cell types, which triggers the inhibition of meristem maintenance and cell elongation. In this report, we show that DOMON domain-containing proteins are key molecular players controlling root development upon phosphate deficiency and ammonium toxicity via iron dynamics.

plant biology↗

bioRxiv2024

Editing cis-elements of OsPHO1;2 improved phosphate transport and yield in rice

Increasing grain yield is the main aim of crop improvement, which is globally impacted by the low availability of soil phosphate (Pi). Overexpressing Pi transporters for increasing Pi uptake often result in Pi toxicity and growth retardation. Despite advancements in genetic engineering, targeting cis-regulatory motifs of Pi transporters remains underexplored for understanding plant mechanisms and improving Pi status. Here, we demonstrated that the excision of the transcription inhibitor motif from the promoter of Pi transporter, OsPHO1;2, enhanced its expression and increased root-to-shoot Pi transport, leading to improved grain yield. Using, in-silico and DNA-protein interaction studies, we show the role of OsWRKY6 transcription factor in the negative regulation of OsPHO1;2 expression by binding to the cis-regulatory element (W-box) present in its promoter. oswrky6 knockout lines displayed a higher OsPHO1;2 expressions, and improved shoot Pi levels. Further, we engineered the OsPHO1;2 promoter for precisely removing the W-box and enhancing OsPHO1;2 expression. The phenotypic and physiological evaluation at the vegetative stage shows that OsPHO1;2 promoter edited (OsPHO1;2:PE) lines have increased shoot length, plant biomass and more root-shoot Pi export under low and normal P conditions. Notably, the 33Pi uptake assay reveals that OsPHO1;2:PE lines exhibited enhanced root Pi uptake, supported by higher root-associated Pi transporters (OsPHTs) expression. An extensive agronomical assessment revealed that OsPHO1;2:PE lines acquire increased seed and panicle numbers, thereby increasing yield without affecting seed quality. Our findings offer valuable insight into the potential of promoter editing to raise plants with better Pi use and improved crop yield.

plant biology↗

bioRxiv2023

A DOMON domain-cytochrome b561 protein acts as a ferric reductase in iron homeostasis and impacts primary root growth under phosphate deficiency

Iron (Fe) and phosphate (Pi) are essential nutrients for plant growth. Several interactions between Fe and Pi homeostasis have been described, such as the Fe-dependent inhibition of primary root growth under Pi deficiency. This response involves the formation of apoplastic Fe+3-malate complexes in the root meristem which implicates the oxidation of Fe+2 by the LPR1 ferroxidase. However, how is the reduced Fe+2 generated in the root meristem and the Fe+3/Fe+2 ratio regulated is unknown. Here, we have identified a gene in Arabidopsis thaliana, named CRR, that is implicated in primary root growth under Pi deficiency. Under low-Pi conditions, the crr mutant showed an enhanced reduction of primary root growth that was associated with increased accumulation of apoplastic Fe in the root meristem and a reduction in meristematic cell division. Conversely, CRR overexpression rendered primary root growth insensitive to low-Pi inhibition, reduced root apoplastic Fe deposition, and impacted the expression of genes involved in Fe and redox homeostasis. CRR is a member of an uncharacterized CYBDOM protein family possessing a cytochrome b561 (CYB561) with an N-terminal DOMON domain. We demonstrated that CRR localizes to the plasma membrane and possesses ascorbate-dependent ferric reductase activity. The crr single mutant and the crr hyp1 double mutant, which harbored a null allele in another member of the CYDOM family, showed increased tolerance to high-Fe stress upon germination and seedling growth. In contrast, CRR overexpression was associated with increased uptake and translocation of Fe to the shoot and resulted in plants highly sensitive to Fe excess toxicity. Our results thus identify a ferric reductase implicated in root Fe acquisition and homeostasis and reveal a biological role for CYBDOM proteins in plants.

plant biology↗

bioRxiv2022

Endoplasmic reticulum calnexins participate in the primary root growth response to phosphate deficiency

Accumulation of incompletely folded proteins in the endoplasmic reticulum (ER) leads to ER stress, activates ER protein degradation pathways, and upregulates genes involved in protein folding (Unfolded Protein Response; UPR). ER stress has been associated with abiotic stress conditions that affect protein folding, including salt stress. However, the role of ER protein folding in plant responses to nutrient deficiencies is unclear. We analyzed several Arabidopsis thaliana mutants affected in ER protein quality control and established that both CALNEXIN (CNX) genes function in the primary roots response to phosphate (Pi) deficiency. CNX and calreticulin (CRT) are homologous ER lectins that bind to N-glycosylated proteins to promote their folding. Growth of cnx1-1 and cnx2-2 single mutants was similar to that of the wild type under high and low Pi conditions, but the cnx1-1 cnx2-2 double mutant showed decreased primary root growth under low Pi conditions due to reduced meristematic cell division. This phenotype was specific to Pi deficiency; the double mutant responded normally to osmotic and salt stress. The root growth phenotype was Fe dependent and was associated with Fe accumulation in the root. Two genes involved in Fe-dependent inhibition of root growth under Pi deficiency, the ferroxidase gene LPR1 and P5-type ATPase PDR2, are epistatic to CNX1/CNX2. Overexpressing PDR2 failed to complement the cnx1-1 cnx2-2 root phenotype. cnx1-1 cnx2-2 showed no evidence of UPR activation, indicating a limited effect on ER protein folding. CNX might process a set of N-glycosylated proteins specifically involved in the response to Pi deficiency. One sentence summaryCalnexin, a lectin chaperone engaged in the folding of N-glycosylated proteins in the ER, participates in primary root adaptation to low phosphate conditions.

plant biology↗

bioRxiv2020

Alternative promoter usage modulates miRNA-guided translation inhibition of a m6A reader in phosphate starvation

Alternative transcription start sites (TSSs) are widespread in eukaryotes. In plants, light, development and tissue regulate selective usage of several TSSs, producing transcripts with distinct 5'UTR as well as shorter protein isoforms with distinct subcellular localization or activity. However, the function of non-coding transcripts generated by alternative TSSs is still largely unknown. We show that phosphate availability regulates numerous alternative TSSs, including a non-coding alternative TSS (ALTECT4) associated with ECT4, encoding a N6-methyladenosine (m6A) reader. We found that ECT4 harbors a cleavage-resistant miR826b target site at its 3UTR, also present in ALTECT4. In the absence of ALTECT4, miR826b guides translation inhibition of ECT4. Phosphate deficiency triggers specific and robust expression of ALTECT4, counteracting miR826b inhibition of its targets, including ECT4. The role of ALTECT4 as a miR826b antagonist shows that it acts in cis to regulate translation of the m6A reader ECT4, and this function might be shared among other non-coding transcripts generated by alternative TSS.

plant biology↗

bioRxiv2020

The transcription and export complex THO/TREX contributes to transcription termination in plants

Transcription termination has important regulatory functions, impacting mRNA stability, localization and translation potential. Failure to appropriately terminate transcription can also lead to read-through transcription and the synthesis of antisense RNAs which can have profound impact on gene expression. The Transcription-Export (THO/TREX) protein complex plays an important role in coupling transcription with splicing and export of mRNA. However, little is known about the role of the THO/TREX complex in the control of transcription termination. In this work, we show that two proteins of the THO/TREX complex, namely TREX COMPONENT 1 (TEX1 or THO3) and HYPER RECOMBINATION1 (HPR1 or THO1) contribute to the correct transcription termination at several loci in Arabidopsis thaliana. We first demonstrate this by showing defective termination in tex1 and hpr1 mutants at the nopaline synthase (NOS) terminator present in a T-DNA inserted between exon 1 and 3 of the PHO1 locus in the pho1-7 mutant. Read-through transcription beyond the NOS terminator and splicing-out of the T-DNA resulted in the generation of a near full-length PHO1 mRNA (minus exon 2) in the tex1 pho1-7 and hpr1 pho1-7 double mutants, with enhanced production of a truncated PHO1 protein that retained phosphate export activity. Consequently, the strong reduction of shoot growth associated with the severe phosphate deficiency of the pho1-7 mutant was alleviated in the tex1 pho1-7 and hpr1 pho1-7 double mutants. Additionally, we show that RNA termination defects in tex1 and hpr1 mutants leads to 3UTR extensions in several plant genes. These results demonstrate that THO/TREX complex contributes to the regulation of transcription termination. Author summaryProduction of messenger RNAs (mRNAs) involves numerous steps including initiation of transcription, elongation, splicing, termination, as well as export out of the nucleus. All these steps are highly coordinated and failure in any steps has a profound impact on the level and identity of mRNAs produced. The THO/TREX protein complex is associated with nascent RNAs and contributes to several mRNA biogenesis steps, including splicing and export. However, the contribution of the THO/TREX complex to mRNA termination was poorly defined. We have identified a role for two components of the THO/TREX complex, namely the proteins TEX1 and HPR1, in the control of transcription termination in the plant Arabidopsis thaliana. We show that the tex1 and hpr1 mutants have defects in terminating mRNA at the nopaline synthase (NOS) terminator found in T-DNA insertion mutants leading to the transcriptional read-through pass the NOS terminator. We also show that tex1 and hpr1 mutants have defects in mRNA termination at several endogenous genes, leading to the production of 3UTR extensions. Together, these results highlight a role for the THO/TREX complex in mRNA termination.

plant biology↗