Vacuolar H^(+)-ATPase and BZR1 form a feedback loop to regulate the homeostasis of BR signaling inArabidopsis

Brassinosteroid(BR)is a vital plant hormone that regulates plant growth anddevelopment.BRASSINAZOLE RESISTANT1(BZR1)is a key transcription factor in BR signaling,and its nucleocytoplasmic localization is crucial for BR signaling.However,the mechanisms that regulate BzR1 nucleocytoplasmic distribution and thus the homeostasis of BR signaling remain largely unclear.The vacuole is the largest organelle in mature plantcells and plays a key role in maintenance of cell ular pH,storage of intracellular substances,and transport ofions.In this study,weuncovered anovel mechanismof BR signaling homeostasis regulatedbythe vacuolar H+-ATPase(V-ATPase)and BZR1 feedback loop.Our results revealed that the vha-a2 vha-a3 mutant(vha2,lacking V-ATPase activity)exhibits enhanced BR signaling with increased total amount of BZR1,nuclearlocalized BZR1,and the ratio of BZR1/phosphorylated BZR1 in the nucleus.Further biochemical assays revealed that VHA-a2 and VHA-a3 of V-ATPase interact with the BZR1 protein through a domain that is conserved across multiple species.VHA-a2 and VHA-a3 negatively regulate BR signaling by interacting with BzR1 and promoting its retention in the tonoplast.Interestingly,a series of molecular analyses demonstrated that nuclear-localized BZR1 could bind directlyto specific motifs in the promoters of VHA-a2 andVHAa3topromote their expression.Taken together,these results suggest that V-ATPase and BzR1 mayforma feedback regulatory loop to maintain thehomeostasis of BR signaling in Arabidopsis,providing new insights into vacuole-mediated regulation of hormone signaling.

Ovule initiation:the essential step controlling offspring number in Arabidopsis

Seed is the offspring of angiosperms.Plants produce large numbers of seeds to ensure effective reproduction and survival in varying environments.Ovule is a fundamentally important organ and is the precursor of the seed.In Arabidopsis and other plants characterized by multi-ovulate ovaries,ovule initiation determines the maximal ovule number,thus greatly affecting seed number per fruit and seed yield.Investigating the regulatory mechanism of ovule initiation has both scientific and economic significance.However,the genetic and molecular basis underlying ovule initiation remains unclear due to technological limitations.Very recently,rules governing the multiple ovules initiation from one placenta have been identified,the individual functions and crosstalk of phytohormones in regulating ovule initiation have been further characterized,and new regulators of ovule boundary are reported,therefore expanding the understanding of this field.In this review,we present an overview of current knowledge in ovule initiation and summarize the significance of ovule initiation in regulating the number of plant offspring,as well as raise insights for the future study in this field that provide potential routes for the improvement of crop yield.

Global Analysis of Gene Expression Profiles in Brassica napus Developing Seeds Reveals a Conserved Lipid Metabolism Regulation with Arabidopsis thaliana

In order to study Brassica napus fatty acid （FA） metabolism and relevant regulatory networks, a systematic identification of fatty acid （FA） biosynthesis-related genes was conducted. Following gene identification, gene expression profiles during B. napus seed development and FA metabolism were performed by cDNA chip hybridization （〉8000 EST clones from seed）. The results showed that FA biosynthesis and regulation, and carbon flux, were conserved between B. napus and Arabidopsis. However, a more critical role of starch metabolism was detected for B. napus seed FA metabolism and storage-component accumulation when compared with Arabidopsis. In addition, a crucial stage for the transition of seed-to-sink tissue was 17-21 d after flowering （DAF）, whereas FA biosynthesis-related genes were highly expressed pri- marily at 21 DAF. Hormone （auxin and jasmonate） signaling is found to be important for FA metabolism. This study helps to reveal the global regulatory network of FA metabolism in developing B. napus seeds.

Interaction of brassinosteroid and cytokinin promotes ovule initiation and increases seed number per silique in Arabidopsis

Ovule initiation is a key step that strongly influences ovule number and seed yield.Notably,mutants with enhanced brassinosteroid(BR)and cytokinin(CK)signaling produce more ovules and have a higher seed number per silique(SNS)than wild-type plants.Here,we crossed BR-and CKrelated mutants to test whether these phytohormones function together in ovule initiation.We determined that simultaneously enhancing BR and CK contents led to higher ovule and seed numbers than enhancing BR or CK separately,and BR and CK enhanced each other.Further,the BR-response transcription factor BZR1 directly interacted with the CK-response transcription factor ARABIDOPSIS RESPONSE REGULATOR1(ARR1).Treatments with BR or BR plus CK strengthened this interaction and subsequent ARR1 targeting and induction of downstream genes to promote ovule initiation.Enhanced CK signaling partially rescued the reduced SNS phenotype of BR-deficient/insensitive mutants whereas enhanced BR signaling failed to rescue the low SNS of CK-deficient mutants,suggesting that BR regulates ovule initiation and SNS through CK-mediated and-independent pathways.Our study thus reveals that interaction between BR and CK promotes ovule initiation and increases seed number,providing important clues for increasing the seed yield of dicot crops.

ANAC005 is a membrane-associated transcription factor and regulates vascular development in Arabidopsis

Vascular tissues are very important for providing both mechanical strength and long-distance transport. The molecular mechanisms of regulation of vascular tissue develop- ment are still not fully understood. In this study we identified ANACoo5 as a membrane-associated NAC family transcription factor that regulates vascular tissue development. Reporter gene assays showed that ANACoo5 was expressed mainly in the vascular tissues, increased expression of ANACoo5 protein in transgenic Arabidopsis caused dwarf phenotype, reduced xylem differentiation, decreased lignin content, repression of a lignin biosynthetic gene and genes related to cambium and primary wall, but activation of genes related to the secondary wall. Expression of a dominant repressor fusion of ANACoo5 had overall the opposite effects on vascular tissue differ- entiation and lignin synthetic gene expression. The ANACoo5- GFP fusion protein was localized at the plasma membrane, whereas deletion of the last 20 amino acids, which are mostly basic, caused its nuclear localization. These results indicate that ANACoo5 is a cell membrane-associated transcription factor that inhibits xylem tissue development in Arabidopsis.

Prediction model of end-point phosphorus content for BOF based on monotone-constrained BP neural network

Dephosphorization is essential content in the steelmaking process,and the process after the converter has no dephosphorization function.Therefore,phosphorus must be removed to the required level in the converter process.In order to better control the end-point phosphorus content of basic oxygen furnace(BOF),a prediction model of end-point phosphorus content for BOF based on monotone-constrained backpropagation(BP)neural network was established.Through the theoretical analysis of the dephosphorization process,ten factors that affect the end-point phosphorus content were determined as the input variables of the model.The correlations between influencing factors and end-point phosphorus content were determined as the constraint condition of the model.200 sets of data were used to verify the accuracy of the model,and the hit ratios in the range of±0.005%and±0.003%are 94%and 74%,respectively.The fit coefficient of determination of the predicted value and the actual value is 0.8456,and the root-mean-square error is 0.0030;the predictive accuracy is better than that of ordinary BP neural network,and this model has good interpretability.It can provide useful reference for real production and also provide a new approach for metallurgical predictive modeling.

Multiple functions of the vacuole in plant growth and fruit quality

Vacuoles are organelles in plant cells that play pivotal roles in growth and developmental regulation.The main functions of vacuoles include maintaining cell acidity and turgor pressure,regulating the storage and transport of substances,controlling the transport and localization of key proteins through the endocytic and lysosomal-vacuolar transport pathways,and responding to biotic and abiotic stresses.Further,proteins localized either in the tonoplast(vacuolar membrane)or inside the vacuole lumen are critical for fruit quality.In this review,we summarize and discuss some of the emerging functions and regulatory mechanisms associated with plant vacuoles,including vacuole biogenesis,vacuole functions in plant growth and development,fruit quality,and plant-microbe interaction,as well as some innovative research technology that has driven advances in the field.Together,the functions of plant vacuoles are important for plant growth and fruit quality.The investigation of vacuole functions in plants is of great scientific significance and has potential applications in agriculture.

Spectral hardening of cosmic ray protons and helium nuclei in supernova remnant shocks

The observed hardening of the spectra of cosmic ray protons and helium nuclei is studied within the model of nonlinear diffusive shock acceleration of supernova remnants(SNRs). In this model, the injected particles with energies below the spectral "knee" are assumed to be described by two populations with different spectral indexes around 200 GeV. The high-energy population is dominated by the particles with energies above 200 GeV released upstream of the shock of SNR, and the low-energy population is attributed to the particles with energies below 200 GeV released downstream of the shock of SNR. In this scenario, the spectral hardening of cosmic ray protons and helium nuclei observed by PAMELA, AMS-02, and CREAM experiments can be reproduced.

A cucumber NAM domain transcription factor promotes pistil development in Arabidopsis

Introduction Sexual reproduction is a fundamentally important biological process in nature.Unisexual flowers provide a widely used system for studying plant sex organ differentiation.Cucumber(C.sativus L.)generates both unisexual and bisexual flowers,and the sex type is mainly controlled by several ethylene synthases,i.e.,CsACS2,CsACS1G,CsACS11,and CsACO2(Boualem et al.,2008;Martin et al.,2009;Boualem et al.,2015;Chen et al.,2016).The unisexual flowers typically result from the selective suppression of one of the two genders in flower development stages 6–7(Bai et al.,2004).Meanwhile,if the suppression is deactivated,caused by loss-offunction CsACS2(CmACS7 in melon),functional stamens develop to make the flower bisexual(Li et al.,2009).