bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transport-coupled ubiquitination of the borate transporter BOR1 for its boron-dependent degradation
Authors: Yoshinari Akira , Hosokawa Takuya , Beier Marcel Pascal , Oshima Keishi , Ogino Yuka , Hori Chiaki , Takasuka Taichi E , Fukao Yoichiro , Fujiwara Toru , Takano Junpei 
Published: January 2021

Abstract
Plants take up and translocate nutrients through transporters. In Arabidopsis thaliana, the borate exporter BOR1 acts as a key transporter under boron (B) limitation in the soil. Upon sufficient-B supply, BOR1 undergoes ubiquitination and is transported to the vacuole for degradation, to avoid overaccumulation of B. However, the mechanisms underlying B-sensing and ubiquitination of BOR1 are unknown. In this study, we confirmed the lysine-590 residue in the C-terminal cytosolic region of BOR1 as the direct ubiquitination site and showed that BOR1 undergoes K63-linked polyubiquitination. A forward genetic screen identified that amino acid residues located in vicinity of the substrate-binding pocket of BOR1 are essential for the vacuolar sorting. BOR1 variants that lack B-transport activity showed a significant reduction of polyubiquitination and subsequent vacuolar sorting. Coexpression of wild-type (WT) and a transport-defective variant of BOR1 in the same cells showed degradation of the WT but not the variant upon sufficient-B supply. These findings suggest that polyubiquitination of BOR1 relies on its conformational transition during the transport cycle. We propose a model in which BOR1, as a B transceptor, directly senses the B concentration and promotes its own polyubiquitination and vacuolar sorting for quick and precise maintenance of B homeostasis.
Contrasting transcriptional responses toFusarium virguliformecolonization in symptomatic and asymptomatic hosts
Authors: Baetsen-Young Amy , Chen Huan , Shiu Shin-Han , Day Brad 
Published: January 2021

AbstractThe broad host range of Fusarium virguliforme represents a unique comparative system to identify and define differentially induced responses between an asymptomatic monocot host, maize (Zea mays), and a symptomatic eudicot host, soybean (Glycine max). Using a temporal, comparative transcriptome-based approach, we observed that early gene expression profiles of root tissue from infected maize suggest that pathogen tolerance coincides with the rapid induction of senescence dampening transcriptional regulators, including ANACs (Arabidopsis thaliana NAM/ATAF/CUC protein) and Ethylene-Responsive Factors. In contrast, the expression of senescence-associated processes in soybean was coincident with the appearance of disease symptom development, suggesting pathogen-induced senescence as a key pathway driving pathogen susceptibility in soybean. Based on the analyses described herein, we posit that root senescence is a primary contributing factor underlying colonization and disease progression in symptomatic versus asymptomatic host–fungal interactions. This process also supports the lifestyle and virulence of F. virguliforme during biotrophy to necrotrophy transitions. Further support for this hypothesis lies in comprehensive co-expression and comparative transcriptome analyses, and in total, supports the emerging concept of necrotrophy-activated senescence. We propose that F. virguliforme conditions an environment within symptomatic hosts, which favors susceptibility through transcriptomic reprogramming, and as described herein, the induction of pathways associated with senescence during the necrotrophic stage of fungal development.
Exocyst subunit Exo70B2 is linked to immune signaling and autophagy
Authors: Brillada Carla , Teh Ooi-Kock , Ditengou Franck Anicet , Lee Chil-Woo , Klecker Till , Saeed Bushra , Furlan Giulia , Zietz Marco , Hause Gerd , Eschen-Lippold Lennart , Hoehenwarter Wolfgang , Lee Justin , Ott Thomas , Trujillo Marco 
Published: January 2021

AbstractDuring the immune response, activation of the secretory pathway is key to mounting an effective response, while gauging its output is important to maintain cellular homeostasis. The Exo70 subunit of the exocyst functions as a spatiotemporal regulator by mediating numerous interactions with proteins and lipids. However, a molecular understanding of the exocyst regulation remains challenging. We show that, in Arabidopsis thaliana, Exo70B2 behaves as a bona fide exocyst subunit. Conversely, treatment with the salicylic acid (SA) defence hormone analog benzothiadiazole (BTH), or the immunogenic peptide flg22, induced Exo70B2 transport into the vacuole. We reveal that Exo70B2 interacts with AUTOPHAGY-RELATED PROTEIN 8 (ATG8) via two ATG8-interacting motives (AIMs) and its transport into the vacuole is dependent on autophagy. In line with its role in immunity, we discovered that Exo70B2 interacted with and was phosphorylated by the kinase MPK3. Mimicking phosphorylation had a dual impact on Exo70B2: first, by inhibiting localization at sites of active secretion, and second, it increased the interaction with ATG8. Phosphonull variants displayed higher effector-triggered immunity (ETI) and were hypersensitive to BTH, which induce secretion and autophagy. Our results suggest a molecular mechanism by which phosphorylation diverts Exo70B2 from the secretory into the autophagy pathway for its degradation, to dampen secretory activity.
Interdependent evolution of biosynthetic gene clusters for momilactone production in rice
Authors: Kitaoka Naoki , Zhang Juan , Oyagbenro Richard K , Brown Benjamin , Wu Yisheng , Yang Bing , Li Zhaohu , Peters Reuben J 
Published: January 2021

Abstract
Plants can contain biosynthetic gene clusters (BGCs) that nominally resemble those found in microbes. However, while horizontal gene transmission is often observed in microbes, plants are limited to vertical gene transmission, implying that their BGCs may exhibit distinct inheritance patterns. Rice (Oryza sativa) contains two unlinked BGCs involved in diterpenoid phytoalexin metabolism, with one clearly required for momilactone biosynthesis, while the other is associated with production of phytocassanes. Here, in the process of elucidating momilactone biosynthesis, genetic evidence was found demonstrating a role for a cytochrome P450 (CYP) from the other “phytocassane” BGC. This CYP76M8 acts after the CYP99A2/3 from the “momilactone” BGC, producing a hemiacetal intermediate that is oxidized to the eponymous lactone by a short-chain alcohol dehydrogenase also from this BGC. Thus, the “momilactone” BGC is not only incomplete, but also fractured by the need for CYP76M8 to act in between steps catalyzed by enzymes from this BGC. Moreover, as supported by similar activity observed with orthologs from the momilactone-producing wild-rice species Oryza punctata, the presence of CYP76M8 in the other “phytocassane” BGC indicates interdependent evolution of these two BGCs, highlighting the distinct nature of BGC assembly in plants.
Pod shattering in grain legumes: emerging genetic and environment-related patterns
Authors: Parker Travis A , Lo Sassoum , Gepts Paul 
Published: January 2021

AbstractA reduction in pod shattering is one of the main components of grain legume domestication. Despite this, many domesticated legumes suffer serious yield losses due to shattering, particularly under arid conditions. Mutations related to pod shattering modify the twisting force of pod walls or the structural strength of the dehiscence zone in pod sutures. At a molecular level, a growing body of evidence indicates that these changes are controlled by a relatively small number of key genes that have been selected in parallel across grain legume species, supporting partial molecular convergence. Legume homologs of Arabidopsis thaliana silique shattering genes play only minor roles in legume pod shattering. Most domesticated grain legume species contain multiple shattering-resistance genes, with mutants of each gene typically showing only partial shattering resistance. Hence, crosses between varieties with different genes lead to transgressive segregation of shattering alleles, producing plants with either enhanced shattering resistance or atavistic susceptibility to the trait. The frequency of these resistance pod-shattering alleles is often positively correlated with environmental aridity. The continued development of pod-shattering-related functional information will be vital for breeding crops that are suited to the increasingly arid conditions expected in the coming decades.
Two interacting ethylene response factors regulate heat stress response
Authors: Huang Jianyan , Zhao Xiaobo , Bürger Marco , Wang Yurong , Chory Joanne 
Published: January 2021

Abstract
The ethylene response factor (ERF) transcription factors are integral components of environmental stress signaling cascades, regulating a wide variety of downstream genes related to stress responses and plant development. However, the mechanisms by which ERF genes regulate the heat stress response are not well understood. Here, we uncover the positive role of ethylene signaling, ERF95 and ERF97 in basal thermotolerance of Arabidopsis thaliana. We demonstrate that ethylene signaling-defective mutants exhibit compromised basal thermotolerance, whereas plants with constitutively activated ethylene response show enhanced basal thermotolerance. EIN3 physically binds to the promoters of ERF95 and ERF97. Ectopic constitutive expression of ERF95 or ERF97 increases the basal thermotolerance of plants. In contrast, erf95 erf96 erf97 erf98 quadruple mutants exhibit decreased basal thermotolerance. ERF95 and ERF97 genetically function downstream of EIN3. ERF95 can physically interact with ERF97, and this interaction is heat inducible. ERF95 and ERF97 regulate a common set of target genes, including known heat-responsive genes and directly bind to the promoter of HSFA2. Thus, our study reveals that the EIN3-ERF95/ERF97-HSFA2 transcriptional cascade may play an important role in the heat stress response, thereby establishing a connection between ethylene and its downstream regulation in basal thermotolerance of plants.
H3.1K27me1 maintains transcriptional silencing and genome stability by preventing GCN5-mediated histone acetylation
Authors: Dong Jie , LeBlanc Chantal , Poulet Axel , Mermaz Benoit , Villarino Gonzalo , Webb Kimberly M , Joly Valentin , Mendez Josefina , Voigt Philipp , Jacob Yannick 
Published: January 2021

Abstract
Epigenetic mechanisms play diverse roles in the regulation of genome stability in eukaryotes. In Arabidopsis thaliana, genome stability is maintained during DNA replication by the H3.1K27 methyltransferases ARABIDOPSIS TRITHORAX-RELATED PROTEIN 5 (ATXR5) and ATXR6, which catalyze the deposition of K27me1 on replication-dependent H3.1 variants. The loss of H3.1K27me1 in atxr5 atxr6 double mutants leads to heterochromatin defects, including transcriptional de-repression and genomic instability, but the molecular mechanisms involved remain largely unknown. In this study, we identified the transcriptional co-activator and conserved histone acetyltransferase GCN5 as a mediator of transcriptional de-repression and genomic instability in the absence of H3.1K27me1. GCN5 is part of a SAGA-like complex in plants that requires the GCN5-interacting protein ADA2b and the chromatin remodeler CHR6 to mediate the heterochromatic defects in atxr5 atxr6 mutants. Our results also indicate that Arabidopsis GCN5 acetylates multiple lysine residues on H3.1 variants, but H3.1K27 and H3.1K36 play essential functions in inducing genomic instability in the absence of H3.1K27me1. Finally, we show that H3.1K36 acetylation by GCN5 is negatively regulated by H3.1K27me1 in vitro. Overall, this work reveals a key molecular role for H3.1K27me1 in maintaining transcriptional silencing and genome stability in heterochromatin by restricting GCN5-mediated histone acetylation in plants.
EIN2-directed histone acetylation requires EIN3-mediated positive feedback regulation in response to ethylene
Authors: Wang Likai , Zhang Zhiyuan , Zhang Fan , Shao Zhengyao , Zhao Bo , Huang Austin , Tran Jaclyn , Hernandez Fernando Vera , Qiao Hong 
Published: January 2021

Abstract
Ethylene is an important phytohormone with pleotropic roles in plant growth, development, and stress responses. ETHYLENE INSENSITIVE2 (EIN2) mediates the transduction of the ethylene signal from the endoplasmic reticulum membrane to the nucleus, where its C-terminus (EIN2-C) regulates histone acetylation to mediate transcriptional regulation by EIN3. However, no direct interaction between EIN2-C and EIN3 has been detected. To determine how EIN2-C and EIN3 act together, we followed a synthetic approach and engineered a chimeric EIN2-C with EIN3 DNA-binding activity but lacking its transactivation activity (EIN2C–EIN3DB). The overexpression of EIN2C–EIN3DB in either wild-type or in the ethylene-insensitive mutant ein3-1 eil1-1 led to a partial constitutive ethylene response. Chromatin immunoprecipitation sequencing showed that EIN2C–EIN3DB has DNA-binding activity, indicating that EIN3DB is functional in EIN2C–EIN3DB. Furthermore, native EIN3 protein levels determine EIN2C–EIN3DB binding activity and binding targets in a positive feedback loop by interacting with EIN2C–EIN3DB to form a heterodimer. Additionally, although EIN3 does not direct affect histone acetylation levels in the absence of EIN2, it is required for the ethylene-induced elevation of H3K14Ac and H3K23Ac in the presence of EIN2. Together, we reveal efficient and specific DNA-binding by dimerized EIN3 in the presence of ethylene to mediate positive feedback regulation, which is required for EIN2-directed elevation of histone acetylation to integrate into an EIN3-dependent transcriptional activation.
Inverse regulation of light harvesting and photoprotection is mediated by a 3′-end-derived sRNA in cyanobacteria
Authors: Zhan Jiao , Steglich Claudia , Scholz Ingeborg , Hess Wolfgang R , Kirilovsky Diana 
Published: January 2021

Abstract
Phycobilisomes (PBSs), the principal cyanobacterial antenna, are among the most efficient macromolecular structures in nature, and are used for both light harvesting and directed energy transfer to the photosynthetic reaction center. However, under unfavorable conditions, excess excitation energy needs to be rapidly dissipated to avoid photodamage. The orange carotenoid protein (OCP) senses light intensity and induces thermal energy dissipation under stress conditions. Hence, its expression must be tightly controlled; however, the molecular mechanism of this regulation remains to be elucidated. Here, we describe the discovery of a posttranscriptional regulatory mechanism in Synechocystis sp. PCC 6803 in which the expression of the operon encoding the allophycocyanin subunits of the PBS is directly and in an inverse fashion linked to the expression of OCP. This regulation is mediated by ApcZ, a small regulatory RNA that is derived from the 3′-end of the tetracistronic apcABC–apcZ operon. ApcZ inhibits ocp translation under stress-free conditions. Under most stress conditions, apc operon transcription decreases and ocp translation increases. Thus, a key operon involved in the collection of light energy is functionally connected to the expression of a protein involved in energy dissipation. Our findings support the view that regulatory RNA networks in bacteria evolve through the functionalization of mRNA 3′-UTRs.
ERF4 and MYB52 transcription factors play antagonistic roles in regulating homogalacturonan de-methylesterification in Arabidopsis seed coat mucilage
Authors: Ding Anming , Tang Xianfeng , Yang Dahai , Wang Meng , Ren Angyan , Xu Zongchang , Hu Ruibo , Zhou Gongke , O’Neill Malcolm , Kong Yingzhen 
Published: January 2021

Abstract
Homogalacturonan (HG), a component of pectin, is synthesized in the Golgi apparatus in its fully methylesterified form. It is then secreted into the apoplast where it is typically de-methylesterified by pectin methylesterases (PME). Secretion and de-esterification are critical for normal pectin function, yet the underlying transcriptional regulation mechanisms remain largely unknown. Here, we uncovered a mechanism that fine-tunes the degree of HG de-methylesterification (DM) in the mucilage that surrounds Arabidopsis thaliana seeds. We demonstrate that the APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) transcription factor (TF) ERF4 is a transcriptional repressor that positively regulates HG DM. ERF4 expression is confined to epidermal cells in the early stages of seed coat development. The adhesiveness of the erf4 mutant mucilage was decreased as a result of an increased DM caused by a decrease in PME activity. Molecular and genetic analyses revealed that ERF4 positively regulates HG DM by suppressing the expression of three PME INHIBITOR genes (PMEIs) and SUBTILISIN-LIKE SERINE PROTEASE 1.7 (SBT1.7). ERF4 shares common targets with the TF MYB52, which also regulates pectin DM. Nevertheless, the erf4-2 myb52 double mutant seeds have a wild-type mucilage phenotype. We provide evidence that ERF4 and MYB52 regulate downstream gene expression in an opposite manner by antagonizing each other’s DNA-binding ability through a physical interaction. Together, our findings reveal that pectin DM in the seed coat is fine-tuned by an ERF4–MYB52 transcriptional complex.
Plasma membrane nano-organization specifies phosphoinositide effects on Rho-GTPases and actin dynamics in tobacco pollen tubes
Authors: Fratini Marta , Krishnamoorthy Praveen , Stenzel Irene , Riechmann Mara , Matzner Monique , Bacia Kirsten , Heilmann Mareike , Heilmann Ingo 
Published: January 2021

AbstractPollen tube growth requires coordination of cytoskeletal dynamics and apical secretion. The regulatory phospholipid phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) is enriched in the subapical plasma membrane of pollen tubes of Arabidopsis thaliana and tobacco (Nicotiana tabacum) and can influence both actin dynamics and secretion. How alternative PtdIns(4,5)P2 effects are specified is unclear. In tobacco pollen tubes, spinning disc microscopy (SD) reveals dual distribution of a fluorescent PtdIns(4,5)P2-reporter in dynamic plasma membrane nanodomains vs. apparent diffuse membrane labeling, consistent with spatially distinct coexisting pools of PtdIns(4,5)P2. Several PI4P 5-kinases (PIP5Ks) can generate PtdIns(4,5)P2 in pollen tubes. Despite localizing to one membrane region, the PIP5Ks AtPIP5K2-EYFP and NtPIP5K6-EYFP display distinctive overexpression effects on cell morphologies, respectively related to altered actin dynamics or membrane trafficking. When analyzed by SD, AtPIP5K2-EYFP associated with nanodomains, whereas NtPIP5K6-EYFP localized diffusely. Chimeric AtPIP5K2-EYFP and NtPIP5K6-EYFP variants with reciprocally swapped membrane-associating domains evoked reciprocally shifted effects on cell morphology upon overexpression. Overall, active PI4P 5-kinase variants stabilized actin when targeted to nanodomains, suggesting a role of nanodomain-associated PtdIns(4,5)P2 in actin regulation. This notion is further supported by interaction and proximity of nanodomain-associated AtPIP5K2 with the Rho-GTPase NtRac5, and by its functional interplay with elements of Rho of plants signaling. Plasma membrane nano-organization may thus aid the specification of PtdIns(4,5)P2 functions to coordinate cytoskeletal dynamics and secretion.
Live imaging of microtubule organization, cell expansion, and intercellular space formation in Arabidopsis leaf spongy mesophyll cells
Authors: Zhang Liyong , McEvoy Delanie , Le Yen , Ambrose Chris 
Published: January 2021

Abstract
Leaf spongy mesophyll cells form an interconnected network of branched cells and intercellular spaces to maximize the surface area available for light capture and photosynthetic gas exchange. To investigate the morphogenetic events leading to cell separation and branching in Arabidopsis thaliana, we used mesophyll-specific promoters to facilitate imaging of mesophyll cell shape and microtubule (MT) organization over multiple spatiotemporal scales without interference from the overlying epidermal cells. We show that cells enlarge by selective expansion of cell wall regions in contact with intercellular spaces. Cell–cell contacts remain relatively fixed in size, forming the termini of interconnecting branches. Surprisingly, classic schizogeny (de-adhesion of neighboring cells) is relatively infrequent, being related to the local topology of cell junctions during early expansion. Intercellular spaces cue the position of stable MT bundles, which in turn promote efficient dilation of intercellular spaces and cell branching. Our data provide insights into mesophyll morphogenesis and MT organization and lay the groundwork for future investigations.
Natural allelic variation in a modulator of auxin homeostasis improves grain yield and nitrogen use efficiency in rice
Authors: Zhang Siyu , Zhu Limei , Shen Chengbo , Ji Zhe , Zhang Haipeng , Zhang Tao , Li Yu , Yu Jianping , Yang Ning , He Yubing , Tian Yanan , Wu Kun , Wu Juyou , Harberd Nicholas P , Zhao Yunde , Fu Xiangdong , Wang Shaokui , Li Shan 
Published: January 2021

AbstractThe external application of nitrogen (N) fertilizers is an important practice for increasing crop production. However, the excessive use of fertilizers significantly increases production costs and causes environmental problems, making the improvement of crop N-use efficiency (NUE) crucial for sustainable agriculture in the future. Here we show that the rice (Oryza sativa) NUE quantitative trait locus DULL NITROGEN RESPONSE1 (qDNR1), which is involved in auxin homeostasis, reflects the differences in nitrate (NO3−) uptake, N assimilation, and yield enhancement between indica and japonica rice varieties. Rice plants carrying the DNR1indica allele exhibit reduced N-responsive transcription and protein abundance of DNR1. This, in turn, promotes auxin biosynthesis, thereby inducing AUXIN RESPONSE FACTOR-mediated activation of NO3− transporter and N-metabolism genes, resulting in improved NUE and grain yield. We also show that a loss-of-function mutation at the DNR1 locus is associated with increased N uptake and assimilation, resulting in improved rice yield under moderate levels of N fertilizer input. Therefore, modulating the DNR1-mediated auxin response represents a promising strategy for achieving environmentally sustainable improvements in rice yield.
The endosperm-specific transcription factor TaNAC019 regulates glutenin and starch accumulation and its elite allele improves wheat grain quality
Authors: Gao Yujiao , An Kexin , Guo Weiwei , Chen Yongming , Zhang Ruijie , Zhang Xue , Chang Siyuan , Rossi Vincenzo , Jin Fangming , Cao Xinyou , Xin Mingming , Peng Huiru , Hu Zhaorong , Guo Weilong , Du Jinkun , Ni Zhongfu , Sun Qixin , Yao Yingyin 
Published: January 2021

Abstract
In wheat (Triticum aestivum L.), breeding efforts have focused intensively on improving grain yield and quality. For quality, the content and composition of seed storage proteins (SSPs) determine the elasticity of wheat dough and flour processing quality. Moreover, starch levels in seeds are associated with yield. However, little is known about the mechanisms that coordinate SSP and starch accumulation in wheat. In this study, we explored the role of the endosperm-specific NAC transcription factor TaNAC019 in coordinating SSP and starch accumulation. TaNAC019 binds to the promoters of TaGlu-1 loci, encoding high molecular weight glutenin (HMW-GS), and of starch metabolism genes. Triple knock-out mutants of all three TaNAC019 homoeologs exhibited reduced transcript levels for all SSP types and genes involved in starch metabolism, leading to lower gluten and starch contents, and in flour processing quality parameters. TaNAC019 directly activated the expression of HMW-GS genes by binding to a specific motif in their promoters and interacting with the TaGlu-1 regulator TaGAMyb. TaNAC019 also indirectly regulated the expression of TaSPA, an ortholog of maize Opaque2 that activates SSP accumulation. Therefore, TaNAC019 regulation of starch- and SSP-related genes has key roles in wheat grain quality. Finally, we identified an elite allele (TaNAC019-BI) associated with flour processing quality, providing a candidate gene for breeding wheat with improved quality.