Pseudomonas sp. UW4 promotes garlic growth through systemic integration of auxin and ethylene pathways.

With the development of microbial fertilizers, efforts have been made to enrich the strain resources of plant growth-promoting rhizobacteria (PGPR) in maize and to compare the growth-promoting effects of synthetic microbial communities (SynComs) with those of single strains. To achieve this, phenotypic measurements and RNA sequencing (RNA-seq) were performed on maize roots treated with SynComs and single-strain bacterial suspensions, aiming to investigate the regulatory influence of PGPR on differential gene expression and key metabolic pathways in maize roots. In this study, 59 PGPR strains were selected, representing genera including Bacillus, Pseudomonas, Burkholderia sp., Curtobacterium pusillum, Acidovorax, Sphingobium, Mitsuaria, Bacterium, Rhodanobacter, Variovorax, Ralstonia, Brevibacillus, Terrabacter, Flavobacterium, Comamonadaceae, Achromobacter, Paraburkholderia, and Massilia. Based on the growth-promoting effects observed in pot experiments, optimal bacterial strains were selected according to the principles of functional complementarity and functional superposition to construct the SynCom. The selected strains included Burkholderia sp. A2, Pseudomonas sp. C9, Curtobacterium pusillum E2, and Bacillus velezensis F3. The results demonstrated that individual strains exerted measurable growth-promoting effects on seedlings; however, the growth-promoting capability of the SynCom was significantly stronger than that of single strains. The synthetic microbial community ALL group markedly increased root length, shoot fresh weight, shoot dry weight, number of branches, and number of root tips in maize seedlings. RNA-seq analysis of maize roots treated with the SynCom (ALL group) was conducted in comparison with CK, A2, C9, E2, and F3 treatment groups. A total of 5245 differentially expressed genes (DEGs) were identified, of which only 133 were common across treatments. GO and KEGG analyses revealed that DEGs were enriched in multiple biological processes, including cellular amide biosynthetic and metabolic processes, flavonoid biosynthetic and metabolic processes, carbohydrate metabolism, amino acid metabolism, lipid metabolism, and translation. The majority of enriched pathways were associated with primary and secondary metabolism, indicating that these bacterial strains promote plant growth by modulating a wide range of metabolic pathways in plant cells. Overall, this study provides a molecular framework for understanding the mechanisms underlying the growth-promoting effects of SynComs on maize roots and offers valuable insights for future research aimed at identifying key regulatory genes.

Integration of Transcriptome and Metabolome Analyses Reveals the Mechanistic Basis for Cadmium Accumulation in Maize.

Bahiagrass ( Paspalum notatum ) is widely used for slope protection and water and soil conservation in southern China. The plants develop an extensive root system that plays a crucial role in the protection of both soil and water. However, little is currently known about the factors that influence early root growth in bahiagrass. Here, the effects of boron (B), calcium (Ca), iron (Fe), lanthanum (La), cerium (Ce), salicylic acid (SA), and melatonin (MLT) on root growth characteristics were examined. Bahiagrass seedlings were grown in 1/25 strength modified Hoagland nutrient solution supplemented with boric acid, calcium chloride, ferric ethylenediaminetetraacetic acid (Fe-EDTA), lanthanum chloride, cerium chloride, SA, or MLT. Root lengths, root surface areas, and the number of root tips were analyzed using a root scanning system after 2, 4, and 6 days of treatment. We found significant effects on root growth after some treatments. Thus, 0.270 or 0.360 m m B for 2 days enhanced root tip number, whereas 0.15 m m Fe for 6 days increased root surface area. Although 3 or 5 m m Ca caused an increase in root tip numbers, the root length was reduced. The addition of La to the nutrient solution significantly increased root length and surface area, and addition of Ce increased root surface area and root tip numbers. Root growth characteristics were optimal after 0.3 μ m La for 6 days or 1.0 μ m La for 4 days. For Ce treatment, optimal root characteristics were observed at 0.5 μ m Ce for 6 days. Root tip numbers increased after 0.1 or 1.0 μ m MLT for 6 days, whereas SA treatment reduced the root length, surface area, and root tip numbers. Overall, the analyses indicate that treatment with B, Fe, La, Ce, and MLT benefited root growth in bahiagrass seedlings.

The chemical 2,4-dichlorophenoxyacetic acid (2,4-D) regulates plant growth and development and mimics auxins in exhibiting a biphasic mode of action. Although gene regulation in response to the natural auxin indole acetic acid (IAA) has been examined, the molecular mode of action of 2,4-D is poorly understood. Data from biochemical studies, (Grossmann (2000) Mode of action of auxin herbicides: a new ending to a long, drawn out story. Trends Plant Sci 5:506-508) proposed that at high concentrations, auxins and auxinic herbicides induced the plant hormones ethylene and abscisic acid (ABA), leading to inhibited plant growth and senescence. Further, in a recent gene expression study (Raghavan et al. (2005) Effect of herbicidal application of 2,4-dichlorophenoxyacetic acid in Arabidopsis. Funct Integr Genomics 5:4-17), we have confirmed that at high concentrations, 2,4-D induced the expression of the gene NCED1, which encodes 9-cis-epoxycarotenoid dioxygenase, a key regulatory enzyme of ABA biosynthesis. To understand the concentration-dependent mode of action of 2,4-D, we further examined the regulation of whole genome of Arabidopsis in response to a range of 2,4-D concentrations from 0.001 to 1.0 mM, using the ATH1-121501 Arabidopsis whole genome microarray developed by Affymetrix. Results of this study indicated that 2,4-D induced the expression of auxin-response genes (IAA1, IAA13, IAA19) at both auxinic and herbicidal levels of application, whereas the TIR1 and ASK1 genes, which are associated with ubiquitin-mediated auxin signalling, were down-regulated in response to low concentrations of 2,4-D application. It was also observed that in response to low concentrations of 2,4-D, ethylene biosynthesis was induced, as suggested by the up-regulation of genes encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase. Although genes involved in ethylene biosynthesis were not regulated in response to 0.1 and 1.0 mM 2,4-D, ethylene signalling was induced as indicated by the down-regulation of CTR1 and ERS, both of which play a key role in the ethylene signalling pathway. In response to 1.0 mM 2,4-D, both ABA biosynthesis and signalling were induced, in contrast to the response to lower concentrations of 2,4-D where ABA biosynthesis was suppressed. We present a comprehensive model indicating a molecular mode of action for 2,4-D in Arabidopsis and the effects of this growth regulator on the auxin, ethylene and abscisic acid pathways.

Rhizosphere colonization is a requirement for field applications of plant growth-promoting rhizobacteria (PGPR). Complex signal exchanges and mutual recognition occur between microbes and plants. Here, the phosphate-solubilizing strain Pseudomonas sp. P34, which is a type of PGPR with affinity to wheat, was isolated from a wheat rhizosphere via wheat germ agglutinin. A pTR102 plasmid harboring the luciferase luxAB gene was transferred into P34. The labeled strain (P34-L) was then used to track the temporal and spatial characteristics of rhizosphere colonization and examine the effects of colonization on wheat development. The transcript levels of the phosphate transporter gene TaPT4, a phosphorus deficiency indicator, in wheat roots were monitored by quantitative reverse transcription PCR (qRT-PCR). The results indicated that P34-L could survive within the wheat rhizosphere for a long time and colonize new spaces in the wheat rhizosphere following the elongation of wheat roots. Compared with uninoculated wheat plants, plants inoculated with P34-L exhibited significantly increased phosphorus accumulation in the leaves; seedling and root weight; total root length; root projection area; root surface area; and number of root tips, forks, and crossings, thus demonstrating the great value of applying this strain in wheat production by promoting root growth and dry matter accumulation. The downregulation of TaPT4 transcript levels in the wheat roots also suggested that a high-phosphorus environment was established by P34-L. These results lay a foundation for further research on the relationships between PGPR and their host plants. Moreover, a potentially ideal biofertilizer-producing strain for use in sustainable agriculture was developed.

IntroductionDuring asexual propagation of peach rootstocks, adventitious root (AR) formation is influenced by multiple factors, with exogenous hormone application being a key strategy. However, the molecular mechanisms underlying AR formation remain incompletely understood.MethodsIn this study, we treated ‘GF677’ peach rootstocks with 200 mg/L indole-3-butyric acid (IBA) and analyzed the molecular mechanism of AR formation using transcriptomic, proteomic, and metabolomic analysis.ResultsBy detecting the rooting rate and the ratio of indole-3-acetic acid-to-cytokinin (IAA/CTK), we confirmed that 21 days of treatment with 200 mg/L IBA represented the critical time point for AR formation in ‘GF677’ rootstocks. The transcriptomic analysis identified 3,305 differentially expressed genes (DEGs), the proteomic analysis revealed 1,221 differentially expressed proteins (DEPs), and the metabolomic profiling screened key metabolites, including 10 hormone-associated differential metabolites. Furthermore, KEGG pathway enrichment analysis across the multi-omics datasets identified two core co-enriched pathways: plant hormone signal transduction and biosynthesis of secondary metabolites. Through multi-omics analysis, we identified DEGs and found that genes related to auxin synthesis pathways (GRETCHEN HAGEN3 (GH3), PIN-FORMED (PIN), SMALL AUXIN-UP RNA (SAUR), AUX/IAAs, and IAA-Leucine Resistant 1 (ILR1)), CTK synthesis pathways (Cytokinin Oxidase/Dehydrogenase 7 (CKX7), Zeatin O-Glucosyltransferase (ZOG), and Isopentenyltransferase 3 (IPT3)), transcription factors related to plant hormones (Auxin Response Factor (ARF), Myeloblastosis (MYB), Myelocytomatosis (MYC), Basic Helix-Loop-Helix (bHLH), GAI-RGA-SCR (GRAS), APETALA2/Ethylene Responsive Factor (AP2/ERF), and Basic Leucine Zipper (bZIP)), and phenylpropanoid biosynthesis pathway (4-Coumarate-CoA Ligase (4CL), Phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and Flavonol synthase (FLS)) were significantly affected by IBA treatment. Quantitative real-time PCR (qRT-PCR) validation of eight key DEGs confirmed transcriptomic reliability.ConclusionThese findings suggest that IBA promotes AR formation in peach rootstocks by modulating plant hormone levels and enhancing phenylpropanoid biosynthesis.

Roles of jasmonate and ethylene signalling and their interaction in yeast elicitor-induced biosynthesis of a phytoalexin, beta-thujaplicin, were investigated in Cupressus lusitanica cell cultures. Yeast elicitor, methyl jasmonate, and ethylene all induce the production of beta-thujaplicin. Elicitor also stimulates the biosynthesis of jasmonate and ethylene before the induction of beta-thujaplicin accumulation. The elicitor-induced beta-thujaplicin accumulation can be partly blocked by inhibitors of jasmonate and ethylene biosynthesis or signal transduction. These results indicate that the jasmonate and ethylene signalling pathways are integral parts of the elicitor signal transduction leading to beta-thujaplicin accumulation. Methyl jasmonate treatment can induce ethylene production, whereas ethylene does not induce jasmonate biosynthesis; methyl jasmonate-induced beta-thujaplicin accumulation can be partly blocked by inhibitors of ethylene biosynthesis and signalling, while blocking jasmonate biosynthesis inhibits almost all ethylene-induced beta-thujaplicin accumulation. These results indicate that the ethylene and jasmonate pathways interact in mediating beta-thujaplicin production, with the jasmonate pathway working as a main control and the ethylene pathway as a fine modulator for beta-thujaplicin accumulation. Both the ethylene and jasmonate signalling pathways can be regulated upstream by Ca(2+). Ca(2+) influx negatively regulates ethylene production, and differentially regulates elicitor- or methyl jasmonate-stimulated ethylene production.

Characteristics of late maturity in fruit are good agronomic traits for extending the harvest period and marketing time. However, underlying molecular basis of the late-maturing mechanism in fruit is largely unknown. In this study, RNA sequencing (RNA-Seq) technology was used to identify differentially expressed genes (DEGs) related to late-maturing characteristics from a late-maturing mutant ‘Huawan Wuzishatangju’ (HWWZSTJ) (Citrus reticulata Blanco) and its original line ‘Wuzishatangju’ (WZSTJ). A total of approximately 17.0 Gb and 84.2 M paried-end reads were obtained. DEGs were significantly enriched in the pathway of photosynthesis, phenylpropanoid biosynthesis, carotenoid biosynthesis, chlorophyll and abscisic acid (ABA) metabolism. Thirteen candidate transcripts related to chlorophyll metabolism, carotenoid biosynthesis and ABA metabolism were analyzed using real-time quantitative PCR (qPCR) at all fruit maturing stages of HWWZSTJ and WZSTJ. Chlorophyllase (CLH) and divinyl reductase (DVR) from chlorophyll metabolism, phytoene synthase (PSY) and capsanthin/capsorubin synthase (CCS) from carotenoid biosynthesis, and abscisic acid 8′-hydroxylase (AB1) and 9-cis-epoxycarotenoid dioxygenase (NCED1) from ABA metabolism were cloned and analyzed. The expression pattern of NCED1 indicated its role in the late-maturing characteristics of HWWZSTJ. There were 270 consecutive bases missing in HWWZSTJ in comparison with full-length sequences of NCED1 cDNA from WZSTJ. Those results suggested that NCED1 might play an important role in the late maturity of HWWZSTJ. This study provides new information on complex process that results in the late maturity of Citrus fruit at the transcriptional level.

Characteristics of late maturity in fruits are good agronomic traits for extending the harvest period and marketing time. However, underlying molecular basis of the late-maturing mechanism in fruit is largely unknown. In this study, RNA sequencing (RNA-Seq) technology was used to identify differentially expressed genes (DEGs) related to late-maturing characteristics from a late-maturing mutant ‘Huawan Wuzishatangju’ (HWWZSTJ) (Citrus reticulata Blanco) and its original line ‘Wuzishatangju’ (WZSTJ). A total of approximately 17.0 Gb and 84.2 M paried-end reads were obtained. DEGs were significantly enriched in the pathway of photosynthesis, phenylpropanoid biosynthesis, carotenoid biosynthesis, chlorophyll and abscisic acid (ABA) metabolism. Thirteen candidate transcripts related to chlorophyll metabolism, carotenoid biosynthesis and ABA metabolism were analyzed using real-time quantitative PCR (qPCR) at all fruit maturing stages of HWWZSTJ and WZSTJ. Chlorophyllase (CLH) and divinyl reductase (DVR) from chlorophyll metabolism, phytoene synthase (PSY) and capsanthin/capsorubin synthase (CCS) from carotenoid biosynthesis, abscisic acid 8'-hydroxylase (AB1) and 9-cis-epoxycarotenoid dioxygenase (NCED1) from ABA metabolism were cloned and analyzed. The expression pattern of NCED1 indicates its role in the late-maturing characteristics of HWWZSTJ. There were 270 consecutive bases missing in HWWZSTJ in comparison with full-length sequences of NCED1 cDNA from WZSTJ. Those results suggested that NCED1 might play an important role in late maturity of HWWZSTJ. This study provides new information of complex process that results in late maturity of Citrus fruit at the transcriptional level.

Effect of sugars on ethylene synthesis and responsiveness in harvested broccoli florets

The plant hormone ethylene triggers and enhanced ethylene synthesis in certain ripening fruits and senescing flowers. Unlike most carnation (Dianthus caryophyllus L.) cultivars exhibiting climacteric rise in ethylene production at the onset of senescence, cv. Sandrosa does not show this phenomenon naturally. In order to understand the mechanism of autocatalytic ethylene production, we exposed carnation flowers cv. Sandrosa to ethylene which resulted in an enhanced capacity for ethylene synthesis in the petals. A short time response of one hour was measured for an increase in ACC oxidase activity, about five hours in advance of an increase in ACC synthase activity and ethylene production. The observed enhancement was dependent on the presence of exogeneous ethylene, and could be partially inhibited by prior treatment of the petals with α-amanitin or cycloheximide. The results of the present study suggest that in response to ethylene, activation of an existing enzyme is taking place first. This is followed by an increase in expression of ACC oxidase and ACC synthase mRNAs.

Exogenous carbon promotes plantlet growth by inducing ethylene signaling in grapevine

高寒草地不同径级根形态对围封年限的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱条件下接种AM真菌对小马鞍羊蹄甲幼苗根系的影响 DOI: 10.5846/stxb201601280209 作者: 作者单位: 中国科学院生态环境研究中心,中国科学院生态环境研究中心,中国科学院生态环境研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31170581) Inoculation with arbuscular mycorrhizal fungi enhances the root system of Bauhinia faberi var. microphylla seedlings under drought stress conditions Author: Affiliation: Research center for Eco-Environmental Sciences,Chinese Academy of Sciences,Research center for Eco-Environmental Sciences,Chinese Academy of Sciences,Research center for Eco-Environmental Sciences,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了探讨岷江干旱河谷丛枝菌根真菌(AMF)对寄主植物幼苗根系的影响,通过接种购买的AMF摩西球囊霉菌(Funneliformis mosseae)到优势乡土灌木小马鞍羊蹄甲(Bauhinia faberi var. microphylla)幼苗,在重度、中度和轻度干旱条件下培养3个月,研究不同干旱条件下AMF对幼苗根系形态特征、结构特征、功能性状的影响。方差分析结果表明:(1)3种干旱胁迫条件下,接菌均显著增加了幼苗的根总长、根表面积、根分枝数、根尖数(P < 0.001),在中度胁迫和轻度胁迫下,接菌显著促进根鲜重、根体积的增加(P < 0.001),轻度胁迫条件下接菌幼苗的根鲜重、根总长、根表面积、根体积、根尖数最高并显著高于其它处理,但接菌与未接菌的根平均直径之间没有显著差异;(2)接菌幼苗根系趋向于叉状分支结构,在重度胁迫时,叉状分支趋势更显著(P < 0.001);(3)接菌幼苗的根比例都显著小于未接菌的,但幼苗比根长不存在显著差异。相关分析结果表明:菌根侵染率与根鲜重、根总长、根表面积、根体积、根分枝数、根尖数呈极显著正相关(P < 0.001),与拓扑指数、根比例呈极显著负相关(P < 0.001)。研究表明,在干旱条件下,AMF虽然没有提高生长初期的根系的吸收效率,但接种AMF显著影响幼苗根系形态特征和结构特征,更利于植物适应干旱环境,并且AMF对幼苗根系的促生作用随着干旱胁迫程度减轻而提高。 Abstract:Arbuscular mycorrhizal fungi (AMF) can develop a symbiotic relationship with the roots of most terrestrial plants, which can improve the drought tolerance of the host plants. Based on our previous studies, AMF play a critical role in promoting native plant growth in the arid valley of the Minjiang River, China. Furthermore, the effects of AMF on root growth are as important as their effects on aboverground growth. To understand how plant roots respond to AMF under different drought stress conditions, we designed a completely randomized full factorial pot experiment in a greenhouse in the arid valley of the Minjiang River. We added one common AMF (Funneliformis mosseae, FM) to the roots of seedlings from a dominant native shrub (Bauhinia faberi var. microphylla), using three different drought stress conditions. Continuous drought stress was induced by watering the seedlings with distilled water at one-day intervals for three months at low (40%), medium (60%), and high levels (80%) of the field capacity. At the end of the experiment, we harvested the seedlings, and cleaned their roots with distilled water. We subsequently measured the root fresh weight, scanned the roots with a root scanner (EPSON 11000XL), and obtained variables such as root length, root surface area, root volume, root forks, and number of root tips with WinRhizo. We subsequently analyzed the root architecture and the functional characteristics of the B. faberi seedlings to address the relationship between root development and AMF presence under different levels of drought stress. We used one-way ANOVAs, two-way ANOVAs, LSD fitting methods, and Pearson's correlations for our statistical analyses. Inoculation of FM significantly increased the total root length, root surface area, root forks, and the number of root tips under all three drought stress conditions (P < 0.001). In addition, under medium and high soil water content, it significantly increased root fresh weight and root volume (P < 0.001). More specifically, high soil water conditions resulted in the significantly highest root fresh weight, total root length, root surface area, root volume, and number of root tips after FM addition. Nonetheless, there was no significant difference in average root diameter between inoculated and non-inoculated seedlings. Inoculated seedlings tended to develop a dichotomous branching style, which was more profound at low (40% of field capacity) soil water content (P < 0.001). Furthermore, the root fractions of inoculated seedlings were significantly smaller than the non-inoculated seedlings (P < 0.001). However, there was no significant difference in specific root length among all the treatments. Root fresh weight, root length, root surface area, root volume, root forks, and number of root tips correlated significantly and positively with colonization rate (P < 0.001). In contrast, topological index and root fraction were significantly and negatively correlated with colonization rate (P < 0.001). Overall, we found that, although AMF did not improve the root absorption efficiency in the initial growth period of B. faberi, AMF presence significantly affected seedling root morphology and root functional characteristics. These latter effects enhanced B. faberi seedling growth, which allowed the plants to adapt to drought conditions. Finally, the positive effects of AMF on root growth increased with improving water conditions. 参考文献 相似文献 引证文献

Increased ethylene evolution accompanies seed germination of many species including Pisum sativum L., but only a little is known about the regulation of the ethylene biosynthetic pathway in different seed tissues. Biosynthesis of the direct ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), the expression of ACC oxidase (ACO), and ethylene production were investigated in the cotyledons and embryonic axis of germinating pea seeds. An early onset and sequential induction of ACC biosynthesis, accumulation of Ps-ACO1 mRNA and of ACO activity, and ethylene production were localized almost exclusively in the embryonic axis. Maximal levels of ACC, Ps-ACO1 mRNA, ACO enzyme activity and ethylene evolution were found when radicle emergence was just complete. Treatment of germinating seeds with ethylene alone or in combination with the inhibitor of ethylene action 2,5-norbornadiene showed that endogenous ethylene regulates its own biosynthesis through a positive feedback loop that enhances ACO expression. Accumulation of Ps-ACO1 mRNA and of ACO enzyme activity in the embryonic axis during the late phase of germination required ethylene, whereas Ps-ACS1 mRNA levels and overall ACC contents were not induced by ethylene treatment. Ethylene did not induce ACO in the embryonic axis during the early phase of germination. Ethylene-independent signalling pathways regulate the spatial and temporal pattern of ethylene biosynthesis, whereas the ethylene signalling pathway regulates high-level ACO expression in the embryonic axis, and thereby enhances ethylene evolution during seed germination.