Biology subjects

Monden, K.

Publications and source records attributed to Monden, K..

8 recordsLinked to original sources

bioRxiv2026

LBD-type transcription factors suppress local and systemic nitrogen responses through distinct regulatory pathways

Nitrogen (N) is a major determinant of plant growth and productivity. Because soil N availability and internal N demand fluctuate, plants have evolved sophisticated mechanisms to coordinate N acquisition and utilization at the whole-plant level. However, how this coordination is achieved remains poorly understood. Here, we show that N-inducible LATERAL ORGAN BOUNDARIES DOMAIN transcription factors LBD37, LBD38, and LBD39 (LBDs) function as repressors of local N uptake and assimilation and systemic N-demand signaling in Arabidopsis. Triple mutants lacking these three LBDs displayed enhanced nitrate influx and increased accumulation of nitrate, amino acids, and total N. Transcriptome analysis identified an array of N-starvation- and nitrate-inducible genes derepressed in shoots and roots, including C-TERMINALLY ENCODED PEPTIDE (CEP) and CEP DOWNSTREAM (CEPD) genes, as well as genes involved in N uptake and assimilation. Grafting and genetic analyses revealed that LBDs gate the systemic N-demand signaling relay by repressing CEP and CEPD expression organ-autonomously. We also found that LBDs locally repress genes involved in N uptake and assimilation through a distinct regulatory mechanism. We propose that LBDs are key transcriptional repressors in a regulatory framework for optimizing N acquisition and utilization under fluctuating N conditions at the whole-plant level.

plant biology↗

bioRxiv2025

Cytokinin receptor AHK3 modulates root-to-shoot transport of trans-zeatin type cytokinin

Trans-zeatin (tZ)-type cytokinins (CKs) are synthesized in roots in response to nitrate, transported to shoot via xylem, and coordinate diverse physiological processes in aerial organs. Within this mechanism, the regulation of CK biosynthesis by nitrate signaling via NIN-like protein 7 as well as the loading of tZ-type CKs into xylem by ATP-binding cassette transporter G14 have been well studied. However, the roles of other components remain unclear. Here, we show that CK perception and degradation in roots, as mediated by Arabidopsis histidine kinase 3 (AHK3) and CK oxidase/dehydrogenase 4 (CKX4), modulate xylem tZ-type CKs transport and leaf CK status. Grafting experiments demonstrated that root-specific AHK3 deficiency systemically increased leaf blade area through long-distance signals of root-derived tZ-type CK, perceived by shoot-expressed AHK3. Transcriptome and hormonome analyses revealed that root-specific AHK3 deficiency reduced CKX4 expression in roots, elevating tZ-type CK levels in roots and xylem sap and thereby enhancing leaf CK response. Transfer experiments manipulating root nitrate levels showed that root-specific AHK3 deficiency promoted leaf blade area in a manner dependent on both nitrate and root-derived tZ-type CK signaling. Moreover, both nitrate signals and root-expressed AHK3 are required for maximal CKX4 induction in roots, and root-specific CKX4 deficiency enhanced leaf blade area in a nitrate-dependent manner. These findings reveal a novel mechanism in which an AHK3-CKX4 module governs xylem transport of tZ-type CKs, fine-tuning leaf size according to nitrogen availability in roots. SIGNIFICANCE STATEMENTTo clarify a mechanism that attenuates trans-zeatin-type cytokinin transport from roots to shoots in response to nitrate signaling, this study examined the root-specific role of cytokinin receptors. Our results show that cytokinin perception and degradation, as mediated by Arabidopsis histidine kinase 3 and cytokinin oxidase/dehydrogenase 4, modulate xylem trans-zeatin-type cytokinin transport, thereby fine-tuning leaf cytokinin status and growth in a nitrate-dependent manner, providing new insights into long-distance cytokinin transport according to nitrogen availability.

plant biology↗

bioRxiv2025

Arabidopsis root-type ferredoxin:NADP(H) oxidoreductases are crucial for root growth and ferredoxin-dependent processes

Root-type ferredoxin:NADP(H) oxidoreductase (RFNR) is believed to reduce ferredoxin using NADPH in nonphotosynthetic tissues, facilitating ferredoxin-dependent biological processes. However, the physiological functions of RFNR remain unclear due to the difficulty in obtaining mutants lacking redundant RFNR isoproteins. The present study successfully generated Arabidopsis homozygous rnfr1;2 double mutants by traditional crossing and selection. However, they displayed severely stunted roots, challenging subsequent growth and abundant seed recovery. Notably, grafted plants combining mutant scions with wild-type rootstocks exhibited normal growth and produced abundant mutant seeds. Growth analysis employing reciprocal grafts with the wild-type and mutant plants showed that primary root growth was inhibited only when the rootstock was derived from the mutants. Meanwhile, the absence of RFNR1 and 2 in the scion had no apparent impact on shoot and root growth. Root transcriptome analysis revealed that RFNR1 and 2 deficiency upregulated genes encoding ferredoxin-dependent enzymes and root-type ferredoxin, leading to genome-wide reprogramming associated with cell walls, lipids, photosynthesis, secondary metabolism, and biotic/abiotic stress responses. Thus, Arabidopsis RFNR1 and 2 are crucial for root growth and various ferredoxin-dependent biological processes.

plant biology↗

bioRxiv2024

Shoot nitrate status regulates Arabidopsis shoot growth and systemic transcriptional responses via shoot adenylate isopentenyltransferase 3

Plants systemically regulate growth and gene expression according to their internal nitrate status. Our previous study reported that shoot nitrate accumulation increases shoot expression of adenosine phosphate-ISOPENTENYLTRANSFERASE 3 (IPT3) and shoot levels of N6-({Delta}2-isopentenyl) adenine (iP)-type cytokinins (CKs). IPT3 expression is localized in the phloem, and iP-type CKs, which are synthesized by IPT3, are phloem-mobile. As CKs are a class of phytohormones that control growth and genome-wide gene expression, shoot-expressed IPT3 may mediate the systemic regulation of growth and transcriptomic responses to shoot nitrate status. To examine this, we developed a novel system to manipulate nitrate levels and IPT3 expression in a shoot-specific manner and performed growth analysis, CK determination, and RNA-sequencing. Our results demonstrated that shoot nitrate accumulation significantly promoted shoot growth and elevated shoot concentrations of iP ribotides, iP-7-N-glucoside, and iP-9-N-glucoside through the action of shoot IPT3. Transcriptomic responses to shoot nitrate accumulation were largely tuned by shoot IPT3, with opposite effects in shoots and roots. Shoot IPT3 amplified shoot responses of nitrate-inducible genes and immune response genes to shoot nitrate accumulation, while it dampened root responses of nitrate transport/assimilation genes. This transcriptomic modulation via shoot IPT3 was accompanied by coherent transcriptional changes in genes encoding mobile peptides and transcriptional repressors. Here we present a novel scheme integrating shoot nitrate status responses with CK signaling.

plant biology↗

bioRxiv2024

Alternative oxidase alleviates mitochondrial oxidative stress during limited nitrate reduction in Arabidopsis thaliana

The conversion of nitrate to ammonium, i.e., nitrate reduction, is a major consumer of reductants in plants. Previous studies have reported that the mitochondrial alternative oxidase (AOX) is upregulated under limited nitrate reduction conditions, including no/low nitrate or when ammonium is the sole nitrogen (N) source. Electron transfer from ubiquinone to AOX bypasses the proton-pumping complexes III and IV, thereby consuming reductants efficiently. Thus, upregulated AOX under limited nitrate reduction may dissipate excessive reductants and thereby attenuate oxidative stress. Nevertheless, so far there is no firm evidence for this hypothesis due to the lack of experimental systems to analyze the direct relationship between nitrate reduction and AOX. We therefore developed a novel culturing system for A. thaliana that manipulates activities of nitrate reduction and AOX separately without causing N starvation, ammonium toxicity, and lack of nitrate signal. Using this system we examined genome-wide gene expression and plant growth to better understand the relationship between AOX and nitrate reduction. Here we show that AOX alleviates mitochondrial oxidative stress and sustains plant growth under limited nitrate reduction.

plant biology↗

bioRxiv2023

Structure and function of a YeeE-YeeD complex for sophisticated thiosulfate uptake

Uptake of thiosulfate ions as an inorganic sulfur source from the environment is important for bacterial sulfur assimilation. Recently, a selective thiosulfate uptake pathway involving a membrane protein YeeE (TsuA) in Escherichia coli was characterized. YeeE-like proteins are conserved in some bacteria, archaea, and eukaryotes. However, the precise function of YeeE, along with its potential partner protein in the thiosulfate ion uptake pathway, remained unclear. Here, we assessed selective thiosulfate transport via Spirochaeta thermophila YeeE in vitro and characterized E. coli YeeD (TsuB) as an adjacent and essential protein for YeeE-mediated thiosulfate uptake in vivo. We further showed that S. thermophila YeeD possesses thiosulfate decomposition activity and that a conserved cysteine in YeeD was modified to several forms in the presence of thiosulfate. Finally, the crystal structures of S. thermophila YeeE-YeeD fusion proteins at 3.34-[A] and 2.60-[A] resolutions revealed their interactions. The association was evaluated by a binding assay using purified S. thermophila YeeE and YeeD. Based on these results, a model of the sophisticated uptake of thiosulfate ions by YeeE and YeeD is proposed. 125-character sentenceThe structural study of the YeeE-YeeD membrane protein complex provides insight into the thiosulfate uptake and degradation mechanism.

biochemistry↗

bioRxiv2022

Root-specific activation of plasma membrane H+-ATPase 1 enhances plant growth and shoot accumulation of nutrient elements under nutrient-poor conditions in Arabidopsis thaliana

Plasma membrane (PM) H+-ATPase contributes to nutrient uptake and stomatal opening by creating proton gradient across the membrane. Previous studies report that a dominant mutation in the OPEN STOMATA2 locus (OST2-2D) constitutively activates Arabidopsis PM H+-ATPase 1 (AHA1), which enlarges proton motive force for root nutrient uptake. However, the stomatal opening is also constitutively enhanced in the ost2-2D, causing drought hypersensitivity. To develop plants with improved nutrient acquisition and normal stomatal movement, we generated grafted plants (scion/rootstock : Col-0 (WT)/ost2-2D), and compared their growth and nutrient element content with those of control plants (WT/WT) under two nutrient regimes. WT/ost2-2D shoots had larger weights, rosette diameter, leaf blade area, and content of C, N, K, Ca, S, P, Mg, Na, Mn, B, Co, and Mo under nutrient-poor conditions compared with WT/WT shoots. The root weights and primary root length were greater in WT/ost2-2D plants than in WT/WT plants under both nutrient conditions. These results suggest that root-specific activation of PM H+-ATPase enhances root nutrient uptake, which accelerates the plant growth under nutrient-poor condition. Our study presents a novel approach to improving nutrient uptake efficiency in crops and vegetable for the implementation of low-input sustainable agriculture.

plant biology↗

bioRxiv2021

Root-specific reduction of cytokinin perception enhances shoot growth with an alteration of trans-zeatin distribution in Arabidopsis thaliana

Compelling evidence demonstrates that root-derived cytokinins (CKs) contribute to shoot growth via long-distance transport; therefore, we hypothesized that an increase in root-derived CKs enhances shoot growth. To demonstrate this, we grafted Arabidopsis Col-0 (WT) scion onto rootstock originated from WT or a double-knockout line of CK receptors AHK2 and AHK3 (ahk23) because the knockout line over accumulates CKs in the body due to feedback homeostasis regulation. The grafted plants (scion/rootstock: WT/WT and WT/ahk23) were grown in vermiculite pots or solid media under high and low nitrogen regimes for vegetative growth and biochemical analysis. The root-specific deficiency of AHK2 and AHK3 increased root concentrations of trans-zeatin (tZ)-type and N6-({Delta}2-isopentenyl) adenine (iP)-type CKs, induced CK biosynthesis genes, and repressed CK degradation genes in the root. Shoot growth, shoot concentrations of tZ-type CKs, and shoot expression of CK-inducible marker genes were consistently larger in the WT/ahk23 plants than in the WT/WT plants. Moreover, the root-specific deficiency of AHK2 and AHK3 enhanced shoot growth in the WT scion more strongly than in the ahk23 scion. Given that tZ-type CKs are predominantly produced from iP-type CKs in the root and xylem-mobile, it is concluded that the root-specific reduction of CK perception would enhance shoot growth by increasing the amount of root-derived tZ-type CKs and their perception by the shoot. This study will present a novel approach to improve plant growth and productivity.

plant biology↗