Biology subjects

Mueller-Roeber, B.

Publications and source records attributed to Mueller-Roeber, B..

10 recordsLinked to original sources

bioRxiv2024

Integrating Gene Expression Analysis and Ecophysiological Responses to Water Deficit in Leaves of Tomato Plants

Soil water deficit (WD) is one of the most important abiotic stresses affecting plant survival and crop yield. Despite its economic relevance, many gaps remain in our understanding of how crops respond to WD, especially concerning the synergistic coordination of molecular and ecophysiological adaptations delaying plant damage and mortality. In this study, we investigated the gene expression imposed by a progressive WD and combined it with measurements pointing to key ecophysiological thresholds in leaves of tomato plants. We uncovered the transcriptomic changes in mature leaves at four stages defined by physiological markers relating to different WD intensities: partial stomatal closure, complete stomatal closure, after leaf wilting, and beginning of embolism development in the veins. By identifying key transcription factors (TFs) across these progressively worsening WD stages, we investigated the timing and impact of ABA-(in)dependent gene regulatory pathways during WD. In addition, we compared the transcriptome in young developing versus mature leaves and explored the physiological mechanisms that may explain the higher tolerance to dehydration in younger leaves. By correlating the transcriptomic changes to precise ecophysiological measurements, the combined dataset will serve as a framework for future studies comparing leaf molecular and physiological responses to WD at specific intensities. HighlightIntegrated ecophysiological and gene expression analyses identify key mechanisms underlying the different thresholds of tomato responses to water deficit

plant biology↗

bioRxiv2022

Transcription factor HSFA7b controls ethylene signaling and meristem maintenance at the shoot apical meristem during thermomemory

The shoot apical meristem (SAM) is responsible for overall shoot growth by generating all above-ground structures. Recent research identified that the SAM displays an autonomous heat stress (HS) memory of a previous non-lethal HS event. Considering the importance of the SAM for plant growth it is essential to unlock how its thermomemory is mechanistically controlled. Here, we report that HEAT SHOCK TRANSCRIPTION FACTOR A7b (HSFA7b) plays a crucial role in this process in Arabidopsis. We found that HSFA7b directly regulates ethylene response at the SAM by binding to promoters of key regulators of ethylene signaling including ETHYLENE-INSENSITIVE 3 to establish thermotolerance. Moreover, HSFA7b controls maintenance of the SAM stem cell pool during thermomemory by regulating the expression of the master regulator WUSCHEL through direct transcriptional activation of the SPLAYED chromatin remodelling factor.

plant biology↗

bioRxiv2021

The diversity of quinoa morphological traits and seed metabolic composition

Quinoa (Chenopodium quinoa Willd.) is an herbaceous annual crop of the amaranth family (Amaranthaceae). It is increasingly cultivated for its nutritious grains, which are rich in protein and essential amino acids, lipids, and minerals. Quinoa exhibits a high tolerance towards various abiotic stresses including drought and salinity, which supports its agricultural cultivation under climate change conditions. The use of quinoa grains is compromised by anti-nutritional saponins, a terpenoid class of secondary metabolites deposited in the seed coat; their removal before consumption requires extensive washing, an economically and environmentally unfavorable process; or their accumulation can be reduced through breeding. In this study, we analyzed the seed metabolomes, including amino acids, fatty acids, and saponins, from 471 quinoa cultivars, including two related species, by liquid chromatography - mass spectrometry. Additionally, we determined a large number of agronomic traits including biomass, flowering time, and seed yield. The results revealed considerable diversity between genotypes and provide a knowledge base for future breeding or genome editing of quinoa. O_TBL View this table: org.highwire.dtl.DTLVardef@160e784org.highwire.dtl.DTLVardef@ff8bd1org.highwire.dtl.DTLVardef@13446daorg.highwire.dtl.DTLVardef@11796eeorg.highwire.dtl.DTLVardef@1b607b8_HPS_FORMAT_FIGEXP M_TBL C_TBL

plant biology↗

bioRxiv2021

Dual control of MAPK activities by AP2C1 and MKP1 MAPK phosphatases regulates defence responses in Arabidopsis

Mitogen-activated protein kinase (MAPK) cascades transmit environmental signals and induce stress and defence responses in plants. These signalling cascades are negatively controlled by specific phosphatases of the type 2C Ser/Thr protein phosphatase (PP2C) and dual-specificity phosphatase (DSP) families that inactivate stress-induced MAPKs; however, the interplay between phosphatases of these different types has remained unknown. Our work reveals that different Arabidopsis MAPK phosphatases, the PP2C-type AP2C1 and the DSP-type MKP1, exhibit both specific and overlapping functions in plant stress responses. Each single mutant and ap2c1 mkp1 double mutant displayed enhanced wound-induced activation of MAPKs MPK3, MPK4, and MPK6, as well as induction of a set of transcription factors. Moreover, ap2c1 mkp1 double mutants show an autoimmune-like response, associated with elevated levels the stress hormones salicylic acid and ethylene, and of the phytoalexin camalexin. Interestingly, this phenotype is reduced in ap2c1 mkp1 mpk6 triple mutants, suggesting that the autoimmune-like response is due to MPK6 misregulation. We conclude that the evolutionarily distant MAPK phosphatases AP2C1 and MKP1 contribute crucially to the tight control of MPK6 activity, ensuring appropriately balanced stress signalling and suppression of autoimmune-like responses during plant growth and development. HighlightDouble MAPK phosphatase mutant plants ap2c1 mkp1 exhibit constitutive, autoimmune-like stress responses, dependent on their substrate MAPK MPK6.

plant biology↗

bioRxiv2021

NAC transcription factor RD26 is a regulator of root hair morphogenic plasticity

Root hairs are outgrowths of epidermal cells central for water and nutrient acquisition. Root hair growth is plastically modified by environmental cues. A frequent response to water limitation is active shortening of root hairs, involving largely unknown molecular mechanisms. A root hair-specific cis-regulatory element (RHE) integrates developmental cues with downstream signalling of root hair morphogenesis. Here, we demonstrate NAC transcription factor RD26 to be a key expressional regulator of this drought stress-triggered developmental response in Arabidopsis thaliana. RD26 directly represses RSL4 and RSL1, two master transcription regulators of root hair morphogenesis, by binding RHE. RD26 further represses core cell wall modification genes including expansins (EXPA7, EXPA18), hydroxyproline-rich glycoproteins (LRX1), xyloglucan endotransglucosylases/hydrolases (XTH12, 13, 14, 26), class III peroxidases (PRX44) and plasma membrane H+-ATPase (AHA7) through RHE. Of note, several RD26-repressed genes are activated by RSL4. Thus, by repressing RSL4 and numerous cell wall-related genes, RD26 governs a robust gene regulatory network for restricting root hair growth under drought. A similar regulatory network exists in tomato, indicating evolutionary conservation across species. Significance statementIn plants, root hairs play a vital role for water and nutrient acquisition, soil anchorage, and microbial interactions. During drought stress, root hair growth is suppressed as an adaptive strategy to save cellular energy. We identified NAC transcription factor RD26 as a key regulator of this developmental plasticity in the model plant Arabidopsis thaliana. RD26 directly and negatively controls the transcriptional activity of key root hair developmental genes, RSL1 and RSL4. Furthermore, RD26 suppresses the expression of several functional genes underlying root hair development including numerous cell wall-related genes. RD26 thus governs a robust gene regulatory network underlying the developmental response to drought stress. A similar regulatory network exists in tomato indicating evolutionary conservation of this mechanism across species.

plant biology↗

bioRxiv2021

An HB40 - JUNGBRUNNEN1 - GA 2-OXIDASE regulatory module for gibberellin homeostasis in Arabidopsis

The phytohormones gibberellins (GAs) play fundamental roles in almost every aspect of plant growth and development. Although there is good knowledge about GA biosynthetic and signaling pathways, factors contributing to the mechanisms homeostatically controlling GA levels remain largely unclear. Here, we demonstrate that homeobox transcription factor HB40 of the HD-Zip family in Arabidopsis thaliana regulates GA content at two additive control levels. We show that HB40 expression is induced by GA and in turn reduces the levels of endogenous bioactive GAs by a simultaneous reduction of GA biosynthesis and increased GA deactivation. Hence, HB40 overexpression leads to typical GA-deficiency traits, such as small rosettes, reduced plant height, delayed flowering, and male sterility. In contrast, a loss-of-function hb40 mutation enhances GA-controlled growth. Genome-wide RNA-sequencing combined with molecular-genetic analyses revealed that HB40 directly activates transcription of JUNGBRUNNEN1 (JUB1), a key TF repressing growth by suppressing GA biosynthesis and signaling. HB40 also represses genes encoding GA 2-oxidases (GA2oxs) which are major GA catabolic enzymes. The effect of HB40 is ultimately mediated through induction of nuclear growth-repressing DELLA proteins. Our results thus uncover an important role of the HB40/JUB1/GA2ox/DELLA network in controlling GA homeostasis during plant growth.

plant biology↗

bioRxiv2020

Primary carbohydrate metabolism genes participate in heat stress memory at the shoot apical meristem of Arabidopsis thaliana

Although we have a good understanding of the development of shoot apical meristems (SAM) in higher plants, and the function of the stem cells (SCs) embedded in the SAM, there is surprisingly little known of its molecular responses to abiotic stresses. Here, we show that the SAM of Arabidopsis thaliana senses heat stress (HS) and retains an autonomous molecular memory of a previous non-lethal HS, allowing the SAM to regain growth after exposure to an otherwise lethal HS several days later. Using RNA-seq, we identified genes participating in establishing a SAM-specific HS memory. The genes include HEAT SHOCK TRANSCRIPTION FACTORs (HSFs), of which HSFA2 is essential, but not sufficient, for full HS memory in the SAM, the SC regulators CLAVATA1 (CLV1) and CLV3, and several primary carbohydrate metabolism genes, including FRUCTOSE-BISPHOSPHATE ALDOLASE 6 (FBA6). We found that expression of FBA6 during HS at the SAM complements that of FBA8 in the same organ. Furthermore, we show that sugar availability at the SAM is essential for survival at high-temperature HS. Collectively, plants have evolved a sophisticated protection mechanism to maintain SCs and, hence, their capacity to re-initiate shoot growth after stress release.

plant biology↗

bioRxiv2020

The mammalian CLU homolog FMT controls development and behavior in Arabidopsis

Mitochondria in animals are associated with development, as well as physiological and pathological behaviors. Several conserved mitochondrial genes exist between plants and higher eukaryotes. Yet, comparative mitochondrial function among plant and animal species is poorly understood. Here, we show that FMT (FRIENDLY MITOCHONDRIA) from Arabidopsis thaliana, a highly conserved homolog of the mammalian CLU (CLUSTERED MITOCHONDRIA) gene family encoding mitochondrial proteins associated with developmental alterations and adult physiological and pathological behaviors, affects whole plant morphology and development under salt stress and control conditions. FMT was found to regulate mitochondrial morphology and dynamics as well as germination, root length, and flowering time. Here, we show that it also affects leaf expansion growth, salt stress-responses and hyponasty. Strikingly, FMT impacted the speed of hyponasty with corresponding change in speed of locomotion of CLU heterozygous knockout mice. These observations indicate that homologous genes affect homologous functions in plants and animals offering the possibility to develop plant models for the study of mammalian behaviors.

plant biology↗

bioRxiv2020

The role of trehalose 6-phosphate in shoot branching - local and non-local effects on axillary bud outgrowth in arabidopsis rosettes

- Trehalose 6-phosphate (Tre6P) is a sucrose signalling metabolite that has been implicated in regulation of shoot branching, but its precise role is not understood. - We expressed tagged forms of TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1) to determine where Tre6P is synthesized in arabidopsis (Arabidopsis thaliana), and investigated the impact of localized changes in Tre6P levels, in axillary buds or vascular tissues, on shoot branching in wild-type and branching mutant backgrounds. - TPS1 is expressed in axillary buds and the subtending vasculature, as well as in the leaf and stem vasculature. Expression of a heterologous trehalose-6-phosphate phosphatase (TPP) to lower Tre6P in axillary buds strongly delayed bud outgrowth in long days and inhibited branching in short days. TPP expression in the vasculature also delayed lateral bud outgrowth and decreased branching. Increased Tre6P in the vasculature enhanced branching and was accompanied by higher expression of FLOWERING LOCUS T (FT) and up-regulation of sucrose transporters. Increased vascular Tre6P levels enhanced branching in branched1 but not in ft mutant backgrounds. - These results provide direct genetic evidence of a local role for Tre6P in regulation of axillary bud outgrowth within the buds themselves, and also connect Tre6P with systemic regulation of shoot branching via FT.

plant biology↗

bioRxiv2018

Tomato fruit ripening factor NOR controls leaf senescence

NAC transcription factors (TFs) are important regulators of expressional reprogramming during plant development, stress responses and leaf senescence. NAC TFs also play important roles in fruit ripening. In tomato (Solanum lycopersicum), one of the best characterized NAC involved in fruit ripening is NON-RIPENING (NOR) and the non-ripening (nor) mutation has been widely used to extend fruit shelf life in elite varieties. Here, we show that NOR additionally controls leaf senescence. Expression of NOR increases with leaf age, and developmental as well as dark-induced senescence are delayed in the nor mutant, while overexpression of NOR promotes leaf senescence. Genes associated with chlorophyll degradation as well as senescence-associated genes (SAGs) show reduced and elevated expression, respectively, in nor mutants and NOR overexpressors. Overexpression of NOR also stimulates leaf senescence in Arabidopsis thaliana. In tomato, NOR supports senescence by directly and positively regulating the expression of several senescence-associated genes including, besides others, SlSAG15 and SlSAG113, SlSGR1 and SlYLS4. Finally, we find that another senescence control NAC TF, namely SlNAP2, acts upstream of NOR to regulate its expression. Our data support a model whereby NAC TFs have often been recruited by higher plants for both, the control of leaf senescence and fruit ripening.

plant biology↗