The Mechanism of Exogenous Salicylic Acid and 6-Benzylaminopurine Regulating the Elongation of Maize Mesocotyl.

The elongation of the mesocotyl plays an important role in the emergence of maize deep-sowing seeds. This study was designed to explore the function of exogenous salicylic acid (SA) and 6-benzylaminopurine (6-BA) in the growth of the maize mesocotyl and to examine its regulatory network. The results showed that the addition of 0.25 mmol/L exogenous SA promoted the elongation of maize mesocotyls under both 3 cm and 15 cm deep-sowing conditions. Conversely, the addition of 10 mg/L exogenous 6-BA inhibited the elongation of maize mesocotyls. Interestingly, the combined treatment of exogenous SA-6-BA also inhibited the elongation of maize mesocotyls. The longitudinal elongation of mesocotyl cells was the main reason affecting the elongation of maize mesocotyls. Transcriptome analysis showed that exogenous SA and 6-BA may interact in the hormone signaling regulatory network of mesocotyl elongation. The differential expression of genes related to auxin (IAA), jasmonic acid (JA), brassinosteroid (BR), cytokinin (CTK) and SA signaling pathways may be related to the regulation of exogenous SA and 6-BA on the growth of mesocotyls. In addition, five candidate genes that may regulate the length of mesocotyls were screened by Weighted Gene Co-Expression Network Analysis (WGCNA). These genes may be involved in the growth of maize mesocotyls through auxin-activated signaling pathways, transmembrane transport, methylation and redox processes. The results enhance our understanding of the plant hormone regulation of mesocotyl growth, which will help to further explore and identify the key genes affecting mesocotyl growth in plant hormone signaling regulatory networks.

Exogenous 6-BA enhances salt tolerance of Limonium bicolor by increasing the number of salt glands.

KEY MESSAGE: Exogenous 6-BA can increase endogenous hormone content, improve photosynthesis, decrease Na+ by increasing leaf salt gland density and salt secretion ability, and reduce ROS content so that it can promote L. bicolor growth. 6-benzyl adenine (6-BA) is an artificial cytokinin and has been widely applied to improving plant adaptation to stress. However, it is rarely reported that 6-BA alleviates salt damage of halophytes. In this paper, we treated Limonium bicolor seedlings, a recretohalophyte with high medicinal and ornamental values, with 300 mM NaCl and different concentrations of 6-BA (0.5, 1.0, and 1.5 mg/L) and measured plant growth, physiological index, the density of salt gland, and the salt secretion ability of leaves. The results showed that exogenous applications 1.0 mg/L 6-BA significantly improved plant growth and photosynthesis, increased cytokinin and auxins contents, K+ and organic soluble matter contents, the activities of SOD, CAT, APX, and POD, and decreased Na+, H2O2, and O2- contents compared to that treated with 300 mM NaCl. Further research showed that exogenous 6-BA significantly increased the density of salt gland and the salt secretion ability of leaves by upregulating the expression of the salt gland developmental genes, therefore, can secrete more excess Na+, and thus reduces the Na+ concentration in leaves, which can alleviate Na+ damage to the species. In all, exogenous 1.0 mg/L 6-BA can increase endogenous hormone, improve photosynthesis, decrease Na+ by increasing secretion ability, and reduce ROS content of L. bicolor so that it can improve the growth. These results above systematically prove the new role of 6-BA in salt tolerance of L. bicolor.

Bracelet salt glands of the recretohalophyte Limonium bicolor: Distribution, morphology, and induction.

Halophytes complete their life cycles in saline environments. The recretohalophyte Limonium bicolor has evolved a specialized salt secretory structure, the salt gland, which excretes Na+ to avoid salt damage. Typical L. bicolor salt glands consist of 16 cells with four fluorescent foci and four secretory pores. Here, we describe a special type of salt gland at the base of the L. bicolor leaf petiole named bracelet salt glands due to their beaded-bracelet-like shape of blue auto-fluorescence. Bracelet salt glands contain more than 16 cells and more than four secretory pores. Leaf disc secretion measurements and non-invasive micro-test techniques indicated that bracelet salt glands secrete more salt than normal salt glands, which helps maintain low Na+ levels at the leaf blade to protect the leaf. Cytokinin treatment induced bracelet salt gland differentiation, and the developed ones showed no further differentiation when traced with a living fluorescence microscopy imager, even though new salt gland development and leaf expansion were observed. Transcriptome revealed a NAC transcription factor gene that participates in bracelet salt gland development, as confirmed by its genome editing and overexpression in L. bicolor. These findings shed light on bracelet salt gland development and may facilitate the engineering of salt-tolerant crops.

Changes in DNA Methylation in Response to 6-Benzylaminopurine Affect Allele-Specific Gene Expression in Populus Tomentosa.

Cytokinins play important roles in the growth and development of plants. Physiological and photosynthetic characteristics are common indicators to measure the growth and development in plants. However, few reports have described the molecular mechanisms of physiological and photosynthetic changes in response to cytokinin, particularly in woody plants. DNA methylation is an essential epigenetic modification that dynamically regulates gene expression in response to the external environment. In this study, we examined genome-wide DNA methylation variation and transcriptional variation in poplar (Populus tomentosa) after short-term treatment with the synthetic cytokinin 6-benzylaminopurine (6-BA). We identified 460 significantly differentially methylated regions (DMRs) in response to 6-BA treatment. Transcriptome analysis showed that 339 protein-coding genes, 262 long non-coding RNAs (lncRNAs), and 15,793 24-nt small interfering RNAs (siRNAs) were differentially expressed under 6-BA treatment. Among these, 79% were differentially expressed between alleles in P. tomentosa, and 102,819 allele-specific expression (ASE) loci in 19,200 genes were detected showing differences in ASE levels after 6-BA treatment. Combined DNA methylation and gene expression analysis demonstrated that DNA methylation plays an important role in regulating allele-specific gene expression. To further investigate the relationship between these 6-BA-responsive genes and phenotypic variation, we performed SNP analysis of 460 6-BA-responsive DMRs via re-sequencing using a natural population of P. tomentosa, and we identified 206 SNPs that were significantly associated with growth and wood properties. Association analysis indicated that 53% of loci with allele-specific expression had primarily dominant effects on poplar traits. Our comprehensive analyses of P. tomentosa DNA methylation and the regulation of allele-specific gene expression suggest that DNA methylation is an important regulator of imbalanced expression between allelic loci.

Transcriptomic analysis reveals the regulatory module of apple (Malus × domestica) floral transition in response to 6-BA.

BACKGROUND: Insufficient production of flower buds is an intractable problem in 'Fuji' apple orchards. Although cytokinin (CK) promotes flower bud formation in apple trees, little is known about the mechanisms regulating this phenomenon. RESULTS: In the present study, high-throughput RNA sequencing (RNA-Seq) of 'Nagafu No. 2' buds was conducted to characterize the transcriptional response to 6-BA treatment during key period of floral transition. A weighted gene co-expression network analysis (WGCNA) of the differentially expressed genes identified hormone signal transduction pathways, totaling 84 genes were highly correlated with the expression pattern of flowering-time genes. The up-regulation of CK signal components and a gibberellin (GA) signal repressor were found to contribute to the promotion of floral transition. In relative comparison to non-treated buds, a series of sugar metabolism- and signal- related genes were associated with relatively high levels of sucrose, fructose, and glucose during floral induction in the 6-BA treated buds. Several transcription factors (i.e. SPLs, SOC1, FD, and COL) that are involved in GA, aging, and photoperiod-regulated flowering pathways were also upregulated by the 6-BA treatment. In addition, potential transcription factors integrating CK signaling to trigger floral induction in apple were also assessed; including PHYTO-CHROME-INTERACTING FACTOR (PIF1,3), WUSCHEL-related homeobox (WOX3,13), and CK response regulators (ARR2). CONCLUSIONS: The present study provides insight into the response of flowering and development-related pathways and transcription factors to 6-BA during the period of floral transition in apple. It extends our knowledge of the fundamental mechanisms associated with CK-regulated floral transition in apple trees.

Comparative transcriptome analysis reveals the regulatory networks of cytokinin in promoting the floral feminization in the oil plant Sapium sebiferum.

BACKGROUND: Sapium sebiferum, whose seeds contain high level of fatty acids, has been considered as one of the most important oil plants. However, the high male to female flower ratio limited the seed yield improvement and its industrial potentials. Thus, the study of the sex determination in S. sebiferum is of significant importance in increasing the seed yield. RESULTS: In this study, we demonstrated that in S. sebiferum, cytokinin (CK) had strong feminization effects on the floral development. Exogenous application with 6-benzylaminopurine (6-BA) or thidiazuron (TDZ) significantly induced the development of female flowers and increased the fruit number. Interestingly, the feminization effects of cytokinin were also detected on the androecious genotype of S. sebiferum which only produce male flowers. To further investigate the mechanism underlying the role of cytokinin in the flower development and sex differentiation, we performed the comparative transcriptome analysis of the floral buds of the androecious plants subjected to 6-BA. The results showed that there were separately 129, 352 and 642 genes differentially expressed at 6 h, 12 h and 24 h after 6-BA treatment. Functional analysis of the differentially expressed genes (DEGs) showed that many genes are related to the hormonal biosynthesis and signaling, nutrients translocation and cell cycle. Moreover, there were twenty one flowering-related genes identified to be differentially regulated by 6-BA treatment. Specifically, the gynoecium development-related genes SPATULA (SPT), KANADI 2 (KAN2), JAGGED (JAG) and Cytochrome P450 78A9 (CYP79A9) were significantly up-regulated, whereas the expression of PISTILLATA (PI), TATA Box Associated Factor II 59 (TAFII59) and MYB Domain Protein 108 (MYB108) that were important for male organ development was down-regulated in response to 6-BA treatment, demonstrating that cytokinin could directly target the floral organ identity genes to regulate the flower sex. CONCLUSIONS: Our work demonstrated that cytokinin is a potential regulator in female flower development in S. sebiferum. The transcriptome analysis of the floral sex transition from androecious to monoecious in response to cytokinin treatment on the androecious S. sebiferum provided valuable information related to the mechanism of sex determination in the perennial woody plants.

[Effects of plant growth regulators and nitrogen on germination of Epimedium pseudowushanense after its stems and leaves reaped].

In order to explore appropriate measures to promote germination after the harvest of Epimedium pseudowushanense, 6-BA, urea, ammonium bicarbonate and GA3 were chosen to spray on the root and rhizomes, and then the biological indicators such as branches, leaf length, leaf width, plant height and so on, were measured in different periods, and the contents of epimedin A, epimedin B, epimedin C and icariin in the dry leaves were detected by HPLC. Results showed that 6-BA 90 mg·L⁻¹(B1), 6-BA 60 mg·L⁻¹(B2),6-BA 30 mg·L⁻¹+urea 300 mg·L⁻¹ (C1), 6-BA 60 mg·L⁻¹+urea 300 mg·L⁻¹(C2),6-BA 60 mg·L⁻¹+ ammonium bicarbonate 300 mg·L⁻¹(C4) significantly increased bud germination in the early period, and the plants quickly set up new system of photosynthesis, the branches in a month of which were higher than the control group respectively by 165.9%, 115.76%, 103.86%, 104.50%, 81.67%.However the branches developed the next year and the dry weight of leaves per plant in group B1 and B2 were much lower than that in control group. The groups that use 6-BA and nitrogen at the same time reaped a good yield of leaves even though the treatment had no significant influence on the branches developed the next year. The dry weight of leaves of C1, C2, C4 treatments were 36.80%, 32.84%, 45.97% more than the control group respectively. Therefore, C1, C2 and C4 treatments are the more appropriate to promote recovery after harvest. Furthermore, different groups, except 10 mg·L⁻¹ 6-BA treatment significantly reduced the content of epimedin C, other groups didn't have any significant effect on the contents of such flavonoids.

6-BA Delays the Senescence of Postharvest Cabbage Leaves by Inhibiting Respiratory Metabolism.

6-BA, a small molecule compound of cytokinins, has been proven to delay leaf senescence in different species, including Chinese flowering cabbage; however, its specific mechanism remains relatively unknown. In this study, the application of external 6-BA delayed leaf senescence in Chinese flowering cabbage, showing that 6-BA effectively prevented the decrease in the maximum quantum yield (Fv/Fm) and overall chlorophyll content and suppressed the expression of the senescence-associated gene BrSAG12 over a 7-day period of storage. Moreover, treatment with 6-BA decreased the respiratory rate, NAD(H) content, the activities of hexose phosphate isomerase (PHI), succinate dehydrogenase (SDH), cytochrome c oxidase (CCO), and ascorbic acid oxidase (AAO) using enzyme-linked immunosorbent assay, and the transcriptional abundance of related genes by real-time quantitative polymerase chain reaction. Furthermore, 6-BA also increased the activity and expression levels of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphate gluconate dehydrogenase (6-PGDH). The group treated with 6-BA retained elevated levels of NADP (H), ATP, total ATPase, and nicotinamide adenine dinucleotide kinase (NADK) activity, as well as the expression of respiratory enzymes. Molecular docking indicated that 6-BA hinders the glycolysis pathway (EMP), tricarboxylic acid cycle (TCA), and cytochrome pathway (CCP), and sustains elevated levels of the pentose phosphate pathway (PPP) through interactions with the PHI, SDH, 6-PGDH, G6PDH, CCO, and AAO proteins, consequently delaying postharvest leaf senescence in Chinese flowering cabbage.

6-BA Reduced Yield Loss under Waterlogging Stress by Regulating the Phenylpropanoid Pathway in Wheat.

Waterlogging stress causes substantial destruction to plant growth and production under climatic fluctuations globally. Plants hormones have been widely explored in numerous crops, displaying an imperative role in crop defense and growth mechanism. However, there is a paucity of research on the subject of plant hormones regulating waterlogging stress responses in wheat crop. In this study, we clarified the role of 6-BA in waterlogging stress through inducing phenylpropanoid biosynthesis in wheat. The application of 6-BA (6-benzyladenine) enhanced the growth and development of wheat plants under waterlogging stress, which was accompanied by reduced electrolyte leakage, high chlorophyll, and soluble sugar content. ROS scavenging was also enhanced by 6-BA, resulting in reduced MDA and H2O2 accumulation and amplified antioxidant enzyme activities. Additionally, under the effect of 6-BA, the acceleration of lignin content and accumulation in the cell walls of wheat tissues, along with the activation of PAL (phenylalanine ammonia lyase), TAL (tyrosine ammonia lyase), and 4CL (4-hydroxycinnamate CoA ligase) activities and the increase in the level of transcription of the TaPAL and Ta4CL genes, were observed under waterlogging stress. Also, 6-BA improved the root growth system under waterlogging stress conditions. Further qPCR analysis revealed increased auxin signaling (TaPR1) in 6-BA-treated plants under waterlogging stress that was consistent with the induction of endogenous IAA hormone content under waterlogging stress conditions. Here, 6-BA also reduced yield loss, as compared to control plants. Thus, the obtained data suggested that, under the application of 6-BA, phenylpropanoid metabolism (i.e., lignin) was stimulated, playing a significant role in reducing the negative effects of waterlogging stress on yield, as evinced by the improved plant growth parameters.

In Vitro Propagation Technology for the Endangered Aquatic Species Nymphoides coronata.

Nymphoides coronata is an endangered aquatic plant species with significant medicinal and ecological importance. To preserve N. coronata from going extinct, we need to provide seedlings and efficient multiplication techniques so that it can be extensively studied. This study aimed to identify the most suitable sterilization treatment, growth medium, and substrate for the cultivation and propagation of N. coronata. Ethanol sterilization, fungicide treatment, and sterile water washing were the most important sterilization steps. A combination of 6-benzylaminopurine (6-BA) and indoleacetic acid (IAA) was the most suitable medium for bud induction and shoot proliferation. The use of α-naphthaleneacetic acid (NAA) increased the rooting rate and rooting time compared to indole-3-butyric acid (IBA). Increasing the concentration of NAA from 0.5 to 1.0 mg/L increased the rooting rate from 78 to 100% and reduced the rooting time from 7 to 5 days. The survival rate of N. coronata seedlings was 100% in a mixture of red soil and sand (1:1, w/w). As a result, the procedure mentioned above could potentially be used to safely propagate this rare species on a large scale. These findings provide valuable insights into the optimal conditions for the successful cultivation and propagation of N. coronata, which can contribute to the conservation and sustainable use of this important rare plant species.

Exogenous 6-BA inhibited hypocotyl elongation under darkness in Picea crassifolia Kom revealed by transcriptome profiling.

Hypocotyl elongation is an important process in plant growth and development, and is under hormonal regulatory signaling pathways. In our study, exogenous 6-BA significantly inhibited Picea crassifolia hypocotyl elongation more than ethylene in the dark, indicating the existence of different regulatory strategies in conifers, therefore, the P. crassifolia transcriptome was studied to explore the responsive genes and their regulatory pathways for exogenous N6-benzyladenine (6-BA) inhibition of hypocotyl elongation using RNA-Sequencing approach. We present the first transcriptome assembly of P. crassifolia obtained from 24.38 Gb clean data. With lowly-expressed and short contigs excluded, the assembly contains roughly 130,612 unigenes with an N50 length of 1,278 bp. Differential expression analysis found 3,629 differentially expressed genes (DEGs) and found that the differential expression fold of genes was mainly concentrated between 2 and 8 (1 ≤ log2FoldChange ≤ 3). Functional annotation showed that the GO term with the highest number of enriched genes (83 unigenes) was the shoot system development (GO: 0048367) and the KEGG category, plant hormone signal transduction (ko04075), was enriched 30 unigenes. Further analysis revealed that several cytokinin dehydrogenase genes (PcCTD1, PcCTD3 and PcCTD6) catabolized cytokinins, while xyloglucan endotransglucosylase hydrolase gene (PcXTH31), WALLS ARE THIN 1-like gene (PcWAT1-1) and Small auxin-induced gene (PcSAUR15) were strongly repressed thus synergistically completing the inhibition of hypocotyl elongation in P. crassifolia. Besides, PcbHLH149, PcMYB44 and PcERF14 were predicted to be potential core TFs that may form a multi-layered regulatory network with the above proteins for the regulation of hypocotyl growth.

Cloning and Functional Analysis of the VfRR17 Gene from tung tree (Vernicia fordii).

Tung tree (Vernicia fordii) is one of the four major woody oilseed species in China. However, its fruit yield is severely hampered by the low number of female flowers and the imbalanced male-to-female flower ratio, which is a problem that restricts the development of the oilseed industry. Previous research has demonstrated that the exogenous application of cytokinins can significantly augment the number of female flowers, although the underlying regulatory mechanism remains elusive. To elucidate the involvement of VfRR17, a member of the A-type ARRs family, in the exogenous cytokinin regulation of flower sexual differentiation in tung tree, this study conducted a comprehensive bioinformatic analysis of the physicochemical properties, structural characteristics, and evolutionary relationships of the protein encoded by VfRR17. Additionally, gene function analysis was performed using subcellular localization, qRT-PCR, and genetic transformation techniques. The findings revealed that the VfRR17 gene's coding region spanned 471 bp, encoding an unstable protein of 156 amino acids with a relative molecular mass of 17.4 kDa. Phylogenetic analysis demonstrated a higher similarity between VfRR17 of the tung tree and the RR17 gene of Jatropha curcas, Ricinus communis, Hevea brasiliensis, and other species within the Euphorbiaceae family compared to other species, with the greatest similarity of 86% observed with the RR17 gene of Jatropha curcas. The qRT-PCR analysis indicated that VfRR17 exhibited high expression levels during the early stage of tung tree inflorescence buds following 6-BA treatment, peaking at 24 h and displaying a 3.47-fold increase compared to that at 0 h. In female and male flowers of the tung tree, the expression in female flowers during the 1 DBF period was significantly higher than in male flowers, exhibiting a difference of approximately 47.91-fold. Furthermore, notable differential expression was observed in the root, leaf, and petiole segments of the tung tree under low-temperature stress at the 12-h time point. In transgenic Arabidopsis, the VfRR17 lines and wild-type lines exhibited significantly different flowering times under an exogenous 6-BA treatment at a concentration of 2 mg/L, with the VfRR17 lines experiencing an 11-day delay compared to the wild-type lines. Additionally, the number of fruit pods in VfRR17 transgenic Arabidopsis lines was significantly reduced by 28 compared to the wild-type lines at a 6-BA concentration of 3 mg/L. These findings suggest that VfRR17 likely plays a critical role in regulating flower development in response to exogenous 6-BA, providing valuable insights into the mechanisms underlying exogenous 6-BA-mediated regulation of female flower development in the tung tree.

The characteristic of Yatu morphogenesis and the efficacy of exogenous hormones on the development of Yatu during fruit development in 'Yali' pear (Pyrus bretschneideri Rehd.).

Yatu is a protuberance formed on the base part of 'Yali' pear fruit, near the pedicel, causing a shape like a duck head termed Yatu. It is a typical phenotypic trait to evaluate fruit appearance quality. The mechanism for Yatu formation has not been clear yet. Here, 90.8% of fruits with Yatu generated in outer base part of fruits. Primitive cells of Yatu were found at 10 days after pollination (DAP). There were higher expression levels of PbGA20ox2, PbIPT7a, and PbIPT5a, lower transcription levels of PbGA2ox1, PbNCED1, and PbNCED3 in outer base part of fruits at 10 DAP, accompanied with significantly higher levels of GA3, ZR, (GA3+ ZR)/ABA, and lower ABA content compared to that in the inner base part of fruits. GA3 + 6-BA promoted Yatu development by increasing GA3 content at 10 and 20 DAP, and ZR content at 20 DAP. PAC suppressed Yatu morphogenesis and development by increasing ABA level at 10 DAP. These results suggest that Yatu usually generated in outer base part of fruits, relatively higher GA3 and ZR contents, lower ABA content promoted Yatu morphogenesis and development.

Nexmifa Regulates Axon Morphogenesis in Motor Neurons in Zebrafish.

Nexmif is mainly expressed in the central nervous system (CNS) and plays important roles in cell migration, cell to cell and cell-matrix adhesion, and maintains normal synaptic formation and function. Nevertheless, it is unclear how nexmif is linked to motor neuron morphogenesis. Here, we provided in situ hybridization evidence that nexmifa (zebrafish paralog) was localized to the brain and spinal cord and acted as a vital regulator of motor neuron morphogenesis. Nexmifa deficiency in zebrafish larvae generated abnormal primary motor neuron (PMN) development, including truncated Cap axons and decreased branches in Cap axons. Importantly, RNA-sequencing showed that nexmifa-depleted zebrafish embryos caused considerable CNS related gene expression alterations. Differentially expressed genes (DEGs) were mainly involved in axon guidance and several synaptic pathways, including glutamatergic, GABAergic, dopaminergic, cholinergic, and serotonergic synapse pathways, according to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation. In particular, when compared with other pathways, DEGs were highest (84) in the axon guidance pathway, according to Organismal Systems. Efna5b, bmpr2b, and sema6ba were decreased markedly in nexmifa-depleted zebrafish embryos. Moreover, both overexpression of efna5b mRNA and sema6ba mRNA could partially rescued motor neurons morphogenesis. These observations supported nexmifa as regulating axon morphogenesis of motor neurons in zebrafish. Taken together, nexmifa elicited crucial roles during motor neuron development by regulating the morphology of neuronal axons.

6-benzylaminopurine exposure induced development toxicity and behaviour alteration in zebrafish (Danio rerio).

6-benzylaminopurine (6-BA) is one of the first synthetic hormones and has been widely used in fruit cultivation, gardening and agriculture. However, excessive use of 6-BA will cause potential harm to the environment and humans. Therefore, our research focused on assessing the impact of 6-BA on the development and neurobehavior of zebrafish. The results showed that 6-BA had little effect on the embryos from 2 hpf to 10 hpf. However, delayed development, decreased survival and hatchability were observed under 30 and 40 mg/L 6-BA from 24 hpf. 6-BA also reduced surface tension of embryonic chorions at 24 hpf. In addition, 6-BA caused abnormal morphology and promoted the accumulation of oxidative stress. Transcription of genes in connection with development and oxidative stress was also strikingly altered. Results of movement assay showed that zebrafish were less active and their behavior was significantly inhibited under the 20 and 30 mg/L 6-BA treatments. Locomotion-related genes th and mao were down-regulated by gradient, while the transcription of dbh was upregulated at a low concentration (2 mg/L) but decreased as the concentration increased. Moreover, 6-BA exposure caused increased arousal and decreased sleep. Sleep/wake related genes hcrt and hcrtr2 were upregulated, but decreased at 30 mg/L, while the mRNA level of aanat2 was reduced in a concentration-dependent manner. To sum up, our results showed that 6-BA induced developmental toxicity, promoted the accumulation of oxidative stress, and damaged locomotion and sleep/wake behavior.

[Effects of exogenous 6-BA on the yield of wheat after rice in the Jianghan Plain under diffe-rent shading treatments]. / 外源6-BAå¯¹ä¸åŒæ—¶æœŸé®å ‰ä¸‹æ±Ÿæ±‰å¹³åŽŸç¨»èŒ¬å°éº¦äº§é‡çš„å½±å“.

The long duration of rainy weather in the Jianghan Plain leads to low light stress to wheat during the growing season. We examined the effects of shading at booting stage (S1) and anthesis (S2) on grain yield and physiological traits of two main wheat cultivars in Jianghan Plain, Zhengmai 9023 (ZM 9023) and Yangmai 23 (YM 23). 6-BA was sprayed before shading treatment (S1+6-BA, S2+6-BA) to explore the mitigation effect of low light stress by 6-BA. The results showed that 45% shading of full solar radiation at booting and anthesis stages significantly reduced grain yield, with greater effect at anthesis than that at the booting stage. Dry matter accumulation of grain during 14-21 days after anthesis was significantly decreased by shading. Shading at both growth stages reduced dry matter accumulation at maturity and changed the proportion of dry matter redistribution in vegetative organs. Consequently, grain yield was more dependent on the storage of photosynthetic assimilates of vegetative organs before anthesis, which resulted in a decline of grain yield in shading treatment. The grain yield of spraying 6-BA before anthesis was significantly greater than that of shading treatment, suggesting exogenous application of 6-BA could delay the senescence of flag leaf, grain filling rate and grain weight to mitigate the negative effect of shading. In addition, spraying 6-BA increased dry matter accumulation in the shading treatment at anthesis, and the translocation of post-anthesis assimilates. Grain weight of S2+6-BA was higher than that with S2, which ultimately increased grain yield as compared to the shading treatment. In conclusion, the negative impact of shading on wheat grain yield at anthesis was greater than that at booting stage. The application of exogenous 6-BA before shading at anthesis could mitigate yield loss of the shading treatment.

Developmental toxicity and alteration of gene expression in zebrafish embryo exposed to 6-benzylaminopurine.

6-benzylaminopurine (6-BA) is widely used in agriculture and horticulture as plant growth regulator. Its excessive use may pose a potential risk to both environment and human health, which is causing great concern. This study was undertaken to assess the acute developmental toxicity of 6-BA to zebrafish embryos based on OECD protocols and mortality, hatching rate and malformation were investigated. Results showed that the 96 h-LC50 and 96 h- EC50 values were 63.29 mg/L and 41.86 mg/L, respectively. No mortality or teratogenic effects were found at concentrations lower than 10 mg/L 6-BA at concentrations higher than 50 mg/L significantly inhibited hatchability and embryo development, induced serious toxicity characterized by morphologic abnormalities (elongated pericardium, heart and yolk sac edema, spine curvature) and functional failure (slow spontaneous movement and heart rate, growth retardation, yolk sac absorption retention). Moreover, 6-BA-induced apoptosis was observed in embryos by the acridine orange staining and confirmed by the apoptotic-related genes, all of which p53 was significantly up-regulated at concentrations higher than 10 mg/L, bax at concentrations higher than 12.5 mg/L, while bcl2 was down-regulated at concentrations higher than 25 mg/L. As for genes of cardiac development, qPCR results demonstrated that nkx2.5, gata5, and amhc were significantly down-regulated at concentrations higher than 25 mg/L, vmhc and atp2a2a at concentration of 50 mg/L, in contrast, hand2 was up-regulated at concentration of 50 mg/L. Our data indicate that 6-BA induces a dose-dependent toxicity resulting in apoptosis through the involvement of p53-dependent pathways and hindering normal heart development in zebrafish embryos.

Optical Pressure Sensor Based on the Emission and Excitation Band Width (fwhm) and Luminescence Shift of Ce3+-Doped Fluorapatite-High-Pressure Sensing.

A novel, contactless optical sensor of pressure based on the luminescence red-shift and bandwidth (full width at half-maximum, fwhm) of the Ce3+-doped fluorapatite-Y6Ba4(SiO4)6F2 powder has been successfully synthesized via a facile solid-state method. The obtained material exhibits a bright blue emission under UV light excitation. It was characterized using powder X-ray diffraction, scanning electron microscopy and luminescence spectroscopy, including high-pressure measurements of excitation and emission spectra, up to above ∼30 GPa. Compression of the material resulted in a significant red-shift of the allowed 4f → 5d and 5d → 4f transitions of Ce3+ in the excitation and emission spectra, respectively. The pressure-induced monotonic shift of the emission band, as well as changes in the excitation/emission band widths, have been correlated with pressure for sensing purposes. The material exhibits a high pressure sensitivity (dλ/d P ≈ 0.63 nm/GPa) and outstanding signal intensity at high-pressure conditions (∼90% of the initial intensity at around 20 GPa) with minimal pressure-induced quenching of luminescence.

[Determination of 6-benzylaminopurine in edible mushrooms by solid liquid extraction with low-temperature partition and high performance liquid chromatography-mass spectrometry].

A simple method based on solid liquid extraction with low-temperature partition (SLE-LTP) coupled with high performance liquid chromatography-mass spectrometry (HPLC-MS) was developed for the determination of 6-benzylaminopurine (6-BA) in edible mushrooms. The samples were extracted with acetonitrile followed by low-temperature partition at -30℃ for 4 h. The separation was performed on a Hitachi LaChrom C18 column (250 mm×4.6 mm, 5 µm) with 0.02 mol/L ammonium acetate (containing 0.1% (v/v) glacial acetic acid)-methanol (6:4, v/v) as the mobile phases with isocratic elution. The compound was detected in positive electrospray ionization mode, and quantified by external standard method. The results showed that the limit of detection (LOD, S/N>3) for the analyte was 0.006 mg/kg, and the limit of quantification (LOQ, S/N>10) was 0.02 mg/kg. The calibration curve showed good linear in the range of 0.05-2.0 mg/L, and the correlation coefficient (r2) was 1.0000. The spiked recoveries were between 81.3% and 93.7% with the relative standard deviations (RSDs, n=6) of 0.7%-2.4% at the spiked levels of 0.1 mg/kg and 0.5 mg/kg. The developed method is simple, reliable and can be applied for the accurate determination of 6-BA residue in edible mushrooms.

[Determination of the plant growth regulators in batatas by matrix solid-phase dispersive extraction and high performance liquid chromatography with tandem mass spectrometry].

An analytical method based on matrix solid-phase dispersive (MSPD) extraction and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established for the determination of forchlorfenuron, 6-benzylaminopurine (6-BA), N-(2-ethylhexyl)-5-norbornene-2,3-dicarboximide (MGK 264) and paclobutrazol in batatas. The samples were dispersed with silica by grinding, and then extracted with methanol. The determination was carried out on a Thermo hypersil GOLD C18 column (150 mm×2.1 mm, 5 µm) in gradient elution with mobile phases of methanol and ammonium formate (5 mmol/L, containing 0.1% (v/v) formic acid) and detected with tandem mass spectrometry using selected reaction monitoring (SRM) mode. The quantification was performed using external standard calibration, and the calibration curves were performed in the ranges of 10.8-216.0 ng/g (forchlorfenuron), 10.8-216.0 ng/g (6-BA), 12.5-250.0 ng/g (MGK 264), 10.2-204.0 ng/g (paclobutrazol) with the correlation coefficients larger than 0.96. The limits of quantification (LOQs) were 0.1-0.3 ng/g. The spiked recoveries at the levels of 50, 100 and 200 ng/g of these four plant growth regulators were in the range of 85.3%-116.0%, and the relative standard deviations were 0.6%-22.7%. This method has advantages of simple operation and good accuracy, and can be used for the quantitative determination of forchlorfenuron, 6-BA, MGK 264 and paclobutrazol in batatas.