Improving dryland maize productivity and water efficiency with heterotrophic ammonia-oxidizing bacteria via nitrification and cytokinin activity

A two-year field experiment conducted under dryland conditions in semi-humid and drought-prone regions of China aimed to assess the effect of ammonia-oxidizing bacterial on maize water use efficiency and yield.A heterotrophic ammonia-oxidizing bacteria(HAOB)strain S2_8_1 was used.Six treatments were applied:(1)no irrigation+HAOB strain(DI),(2)no irrigation+blank culture medium(DM),(3)no irrigation control(DCK),(4)irrigation+HAOB(WI),(5)irrigation+blank culture medium(WM),and(6)irrigation control(WCK).Results revealed that HAOB treatment increased maize growth,yield,and water use efficiency over controls,regardless of whether the year was wet or dry.This improvement was attributed to the accelerated nitrification in the rhizosphere soil due to HAOB inoculation,which subsequently led to increased levels of leaf cytokinins.Overall,these findings suggest that HAOB inoculation holds promise as a strategy to boost water use efficiency and maize productivity in dryland agriculture.

Genomic analysis of isopentenyltransferase genes and functional characterization of TaIPT8 indicates positive effects of cytokinins on drought tolerance in wheat

Cytokinins(CKs)function in plant development and during stress responses,but their role in drought tolerance in wheat is unknown.In the present study,24 isopentenyltransferase(IPT)genes,encoding ratelimiting enzymes in CK biosynthesis were identified in the wheat genome.The chromosomal locations and structures of the genes,protein properties,and phylogenetic relationships were characterized.ATP/ADP TaIPT genes showed tissue-specific expression.TaIPT2,TaIPT7,and TaIPT8 expression was rapidly induced by 0.5–1 h drought treatments,which decreased to low levels after 2 h drought treatment,as did most other TaIPT genes.TaIPT8-5a/5b/5d triple mutants showed decreased levels of tZtype CK under normal and drought conditions and reduced drought tolerance,which,however,did not manifest as phenotype alterations.By contrast,transgenic wheat plants with drought-induced TaIPT8showed increased drought tolerance.Our study provides a foundation for further investigation of TaIPT genes and novel insights into the role of CKs in the drought response of wheat.

白菜型油菜IPT基因家族鉴定及表达分析

异戊烯基转移酶(isopentenyltransferase,IPT)是细胞分裂素生物合成的第一限速酶,为分析IPT基因家族在白菜型油菜生长中的功能,利用生物信息学方法从其基因组中鉴定出13个BrIPT基因,它们不均匀地分布在7条染色体上。BrIPTs可分为4个亚族,各家族成员均含有8~10个保守基序和1~2个UTR区。BrIPT基因的启动子区域包含众多响应元件。BrIPT基因家族成员受环境因子、生物激素及防御与应激调控。qRTPCR结果显示,tRNA-IPT基因BrIPT4、BrIPT6、BrIPT9在白菜型油菜体内各个部位均有表达。相比于苗期,成熟期白菜型油菜IPT基因的表达量更高,为后续深入研究IPT基因家族成员的生理生化功能提供了理论依据。

细胞分裂素受体基因SlHK4突变对番茄开花时间的影响

[目的]本研究旨在解析细胞分裂素受体基因SlHK4突变对番茄开花时间的影响,为揭示细胞分裂素途径调控植物开花的分子机制奠定基础。[方法]以细胞分裂素受体基因SlHK4的2个纯合突变株系slhk4-4和slhk4-5及野生型(WT)番茄为材料,统计各株系开花时间,并在发芽26 d后取植株茎尖进行石蜡切片显微观察、响应细胞分裂素的荧光信号检测以及转录组测序等分析。[结果]slhk4-4和slhk4-5突变体的始花节位与WT相同,但始花时间分别比WT晚6和4 d。与WT相比,slhk4-5茎尖花分生组织分化推迟,细胞显著减小,细胞数目略少;slhk4-4与细胞分裂素响应启动子TCSn驱动的绿色荧光蛋白基因GFP过表达株系的杂交F 1代茎尖中,响应细胞分裂素的GFP荧光信号显著减弱;slhk4-5茎尖中细胞周期正调控基因Cyclin-B1-2表达下调,开花正调控基因FUL2、SOC1表达上调,而花发育基因AGL12和AGL19表达下调,开花调控相关基因的表达变化趋势与slhk4-5开花推迟的性状变化不完全一致。差异表达基因(DEG)的功能分析显示,57.6%具有功能注释的DEG是富集于光合作用、呼吸作用、蛋白合成和代谢等相关通路中的结构基因,其中88.2%在slhk4-5茎尖中的表达下调,表明slhk4茎尖的细胞活性很可能弱于WT。[结论]细胞分裂素受体SlHK4的功能缺失导致slhk4茎尖细胞分裂素信号减弱,花分生组织细胞减小,活性降低,分化延后,进而导致slhk4开花推迟。SlHK4是番茄开花时间的正调控因子。

生长素和细胞分裂素诱导植物胚性愈伤组织研究进展

植物胚性愈伤组织在植物研究与应用中是一种重要的试材,有很多关于植物胚性愈伤组织诱导方法研究的报道。生长素和细胞分裂素被广泛应用于胚性愈伤组织的诱导,是胚性愈伤组织诱导的关键因子。阐述了生长素和细胞分裂素在植物胚性愈伤组织诱导及体细胞胚胎发生过程中的作用,讨论了其在植物胚性愈伤组织诱导中的作用、使用方法与原则,为愈伤组织诱导、愈伤组织胚性化诱导等研究中植物生长调节剂的使用提供依据。

超高效液相色谱-三重四级杆质谱联用法同时测定荔枝中4种细胞分裂素

【目的】应用超高效液相色谱-三重四级杆质谱联用仪(UPLC-MS/MS),建立一种同时测定荔枝反式玉米素核苷(tZR)、异戊烯基腺嘌呤核苷(IPR)、二氢玉米素(DHZ)、异戊烯基腺嘌呤(IP)4种细胞分裂素含量的方法。【方法】0.25 g荔枝样品用乙腈-水(80∶20,体积比)溶液浸提8 h,经Bond Elut Plexa PCX固相萃取柱纯化,2.5%氨水甲醇洗脱后过0.22μm有机滤膜检测。选取XSelect HSS T3色谱柱,以甲醇和5 mmol·L^(-1)甲酸铵水溶液为流动相进行7 min梯度洗脱,采用电喷雾正离子(ESI+)模式电离,选择反应监测(MRM)模式对细胞分裂素进行定量。【结果】4种细胞分裂素的检出限和定量限分别低于18.12和60.39 pg·g^(-1),在0.05~50 ng·mL^(-1)质量浓度范围内呈良好的线性关系,线性相关系数(r2)大于0.999。在高、中、低浓度三种加标水平下,4种细胞分裂素的平均回收率为80.0%~108.2%,标准偏差为0.8%~15.5%。采用建立的方法可以同时检测出荔枝果皮、果肉、种子、幼果、叶片和果柄离区中4种细胞分裂素含量。【结论】该方法简便、快速、灵敏、准确,适用于荔枝不同组织中细胞分裂素含量的测定。

细胞分裂素信号调控植物雌配子体发育的研究进展

雌配子体发育是被子植物有性生殖过程的重要阶段,它的顺利进行是保证植物完成整个生命周期的前提。细胞分裂素是植物自身合成的一类重要激素,广泛参与植物生长发育等一系列生命过程。在综述细胞分裂素代谢、信号感知和转导的基础上,重点介绍细胞分裂素信号在植物雌配子体发育过程中的功能,旨在从细胞分裂素角度揭示植物雌性生殖发育机理,为提高农作物产量及其遗传改良研究提供理论依据。

苜蓿链霉菌TX21抑菌作用确定及促生物质的鉴定

链霉菌是一种重要的微生物资源,具有广泛的应用价值。本研究从土壤中筛选出一株对多种病原菌有抑制效果的菌株,编号TX21,其中对玉蜀黍平脐蠕孢的抑菌效果最优,为50.0%。采用浸种及喷施的方法探究了菌株TX21发酵上清液对水稻种子和黄瓜幼苗的促生效果,结果显示发酵上清液能使水稻种子胚根和胚芽分别增长48.5%和47.1%,黄瓜幼苗根系和鲜重分别增加了37.6%和47.0%,表现出良好的促生作用;通过形态学观察、生理生化和16S r RNA分子生物学鉴定苜蓿链霉菌Streptomyces alfalfae。利用黄瓜子叶叶绿素试验及UHPLC-MS方法明确了发酵上清液的有效促生物质,证实其中含有2-甲硫顺式玉米素核苷(ms^(2)io^(6)A,分子式:C_(16)H_(23)N_(5)O_(5)S)。

5种不同的植物激素对白花前胡种子萌发的影响

目的 研究生长素(IAA)、细胞分裂素(6-BA)、赤霉素(GA3)、脱落酸(ABA)和乙烯(ET)5种植物激素对白花前胡种子萌发的影响。方法 以宁国产并在室温放置12个月的白花前胡种子为材料,把5种不同的植物激素均配制成4个梯度浓度(1×10^(-1)、1×10^(-2)、1×10^(-3)、1×10^(-4)mg·mL^(-1)),对白花前胡种子进行浸种处理。通过培养皿萌发试验,分析种子的发芽率、根长和鲜重的变化情况。结果 在4个梯度范围内,6-BA对白花前胡种子的生长状态整体起抑制作用。把1×10^(-1)mg·mL^(-1)和1×10^(-2)mg·mL^(-1)设置为高浓度,1×10^(-3)mg·mL^(-1)和1×10^(-4)mg·mL^(-1)设置为低浓度。其中6-BA无论是高浓度还是低浓度均对白花前胡种子的生长状态整体起抑制作用。而GA3和ET在高浓度(1×10^(-1)mg·mL^(-1)和 1×10^(-2)mg·mL^(-1))及ABA和IAA在低浓度(1×10^(-3)mg·mL^(-1)和1×10^(-4)mg·mL^(-1))下均对白花前胡种子的萌发率、根长和鲜重都表达出明显的促进作用。结论 植物激素对白花前胡种子的生长发育均有不同程度的影响,其中ET在1×10^(-2)mg·mL^(-1)时,对白花前胡种子的生长发育影响最为显著,白花前胡种子的萌发率,最大根长和最大鲜重均高于其他组。

EXOGENOUS Ca^(2+) INHIBITS SENESCENCE-RETARDING EFFECT OF CYTOKININS IN DETACHED RICE LEAVES

Cytokinins and Ca 2+ singly retarded senescence of detached rice leaves.When Ca 2+ was applied together with cytokinins,the effectiveness of cytokinins was significantly reduced.Ca 2+ and cytokinins did not stimulate ethylene production synergistically,ruling out the possibility that ethylene was involved in the inhibition of cytokinin induced senescence retarding effect by Ca 2+ .The experiment with specific compounds known to increase (Ca ionophore A23187),or decrease (EGTA,LaCl 3,Verapamil,chlorpromazine) cytosolic Ca 2+ level indicated that the elevated cytosolic Ca 2+ retards senescence.

PbGIF1 promoting cell-proliferation in pear fruit is transcriptionally activated by Pb RR1

As a cell proliferation regulator involved in wide biological processes in plants,GRF-INTERACTING FACTOR(GIF)controls different tissues development.However,whether GIF participates in fruit development remains unclear.According to transcriptome data,we identified PbGIF1was highly expressed during fruit development in cytokinins induced parthenocarpy pear.In the present study,the biofunction of PbGIF1 was initially verified.Overexpression of PbGIF1 promoted fruit size of transgenic tomato.The size of flesh fruit was not affected by cell expansion but the cell proliferation was promoted by overexpressing Pb GIF1.The accelerated cell proliferation process was also observed in PbGIF1-overexpressed transgenic pear fruit calli.The transcriptional regulation of cytokinins on PbGIF1 was further confirmed by exogenous CPPU treatments in pear fruitlets.To investigate the underlying mechanism,the cytokinins-responded factor,PbRR1,was further focused on.The results of Yeast-one-hybrid assay suggested that PbRR1 can bind to the promoter sequence of PbGIF1.The transcriptional activation of PbRR1 on PbGIF1 was also confirmed by Dual-Luciferase assays.Taken together,the results showed that cytokinins control pear fruit development via the transcriptional activation of PbGIF1 by PbRR1.

4种化学调控剂对上部烟叶开片及产质量的影响

以烤烟品种鲁烟1号为材料,在胶州进行大田试验,研究打顶后喷施4种化学调控剂(海藻素、赤霉芸苔素、细胞分裂素和光碳核肥)对上部烟叶开片和产质量的影响。结果表明:4种化学调控剂对调控烟株生长及改善烟叶品质均有一定作用。其中,细胞分裂素最能显著促进上部烟叶长、叶宽和叶面积的增加,促进上部叶开片,提高烟叶产量、产值、均价和上等烟及上中等烟比例等经济性状指标,改善烤后上部烟叶物理性状和化学成分协调性,提高烟叶品质。

‘小果甜柿’组织培养中的抗褐化研究

为降低‘小果甜柿’组织培养中的褐化现象,以其组培继代苗为试材,从基本培养基类型、细胞分裂素种类浓度及抗褐化剂种类浓度三个方面,对‘小果甜柿’进行了组织培养中的抗褐化研究。试验结果表明,相对于(1/2N)MS、(3/4N)MS和MS基本培养基,DKW培养基褐化最轻,褐化仅限于植株基部,未扩散至整个培养基而引起严重褐化;单独使用细胞分裂素ZT抗褐化效果较好,而单独使用6-BA或ZT+6-BA组合,褐化程度均较重;抗褐化剂AC和核黄素对‘小果甜柿’组培继代苗褐化有抑制效果,PVP对褐化无抑制效果,AC优于核黄素和PVP,但AC和核黄素会抑制植株生长而影响继代增殖。因此,综合而言,以DKW为基本培养基,添加细胞分裂素ZT(2.0mg/L),不添加抗褐化剂时,‘小果甜柿’组培继代苗增殖及抗褐化效果表现最佳。

Genome-wide comparative analysis of type-A Arabidopsis response regulator genes by overexpression studies reveals their diverse roles and regulatory mechanisms in cytokinin signaling

Cytokinin is a critical growth regulator for various aspects of plant growth and development. In Arabidopsis, cytokinin signaling is mediated by a two-component system-based phosphorelay that transmits a signal from the receptors, through histidine phosphotransfer proteins, to the downstream response regulators （ARRs）. Of these ARRs, type-A ARR genes, whose transcription can be rapidly induced by cytokinin, act as negative regulators of eytokinin signaling. However, because of functional redundancy, the function of type-A ARR genes in plant growth and development is not well understood by analyzing loss-of-function mutants. In this study, we performed a comparative functional study on all ten type-A ARR genes by analyzing transgenic plants overexpressing these ARR genes fused to a MYC epitope tag. Overexpression of ARR genes results in a variety of cytokinin-associated phenotypes. Notably, overexpression of different ARR transgenes causes diverse phenotypes, even between phylogenetically closely-related gene pairs, such as within the ARR3-ARR4 and ARR5-ARR6 pairs. We found that the accumulation of a subset of ARR proteins （ARR3, ARR5, ARR7, ARR16 and ARR17; possibly ARR8 and ARR15） is increased by MG132, a specific proteasomal inhibitor, indicating that stability of these proteins is regulated by proteasomal degradation. Moreover, similar to that of previously characterized ARR5, ARR6 and ARR7, stability of ARR16 and ARR17, possibly including ARR8 and ARR15, is regulated by cytokinin. These results suggest that type-A ARR proteins are regulated by a combinatorial mechanism involving both the cytokinin and proteasome pathways, thereby executing distinctive functions in plant growth and development.

Seasonal changes of endogenous ABA and cytokinins in environmental adaptation of different ecotypes of reed plants

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The BUD2 mutation affects plant architecture through altering cytokinin and auxin responses in Arabidopsis

The ratio of auxin and cytokinin plays a crucial role in regulating aerial architecture by promoting or repressing axillary bud outgrowth. We have previously identified an Arabidopsis mutant bud2 that displays altered root and shoot architecture, which results from the loss-of-function of S-adenosylmethionine decarboxylase 4 （SAMDC4）. In this study, we demonstrate that BUD2 could be induced by auxin, and the induction is dependent on auxin signaling. The mutation of BUD2 results in hyposensitivity to auxin and hypersensitivity to cytokinin, which is confirmed by callus induction assays. Our study suggests that polyamines may play their roles in regulating the plant architecture through affecting the homeostasis of cytokinins and sensitivities to auxin and cytokinin.

TaARR1, a cytokinin response regulator gene in Triticum aestivum, is essential in plant N starvation tolerance via regulating the N acquisition and N assimilation

Plant N starvation response is closely associated with the N signaling components that involve transduction of the low-N cues. In this study, we functionally characterized Ta ARR1, a cytokinin(CK) response regulator gene in Triticum aestivum, in mediating the N starvation adaptation in plants. Ta ARR1 harbors two conserved domains specified by plant ARR family members;subcellular localization analysis indicated its target onto nucleus after endoplasmic reticulum assortment. Ta ARR1 displayed modified expression upon the N starvation stressor, showing upregulated expression in roots and leaves over a 27-h N starvation treatment and whose induced transcripts were gradually recovered along with progression of the N recovery treatment. The tobacco lines overexpressing Ta ARR1 displayed improved low-N stress tolerance, displaying enlarged phenotype, increased biomass and N accumulation, and enhanced glutamine synthetase(GS) activities compared with wild type(WT) following the N starvation treatment. Expression analysis on genes encoding the nitrate transporter(NRT) and GS proteins in Nicotiana tabacum revealed that Nt NRT2.2 and Nt GS3 are upregulated in expression in the N-deprived transgenic lines, whose expression patterns were contrasted to other above family genes that were unaltered on transcripts between the transgenic lines and WT. Transgene analysis validated the function of Nt NRT2.2 and Nt GS3 in regulating N accumulation, GS activity, growth traits, and N use efficiency in plants. These results suggested the internal connection between the Ta ARR1-mediated N starvation tolerance and the modified transcription of distinct N acquisitionand assimilation-associated genes. Our investigation together indicates that Ta ARR1 is essential in plant N starvation adaptation due to the gene function in transcriptionally regulating distinct NRT and GS genes that affect plant N uptake and assimilation under the N starvation condition.

Interactions between cytokinin and nitrogen contribute to grain mass in wheat cultivars by regulating the flag leaf senescence process

Premature senescence after anthesis reduces crop yields.Delaying leaf senescence could maintain photosynthetic activity for a longer period and lead to a higher photosynthetic rate.Recent studies have provided some insights into the interaction between cytokinin and nitrogen(N)in the regulation of plant development.In the present study,foliar application of exogenous 6-benzylaminopurine(6-BA)and lovastatin,an inhibitor of cytokinin synthesis,was combined with three N rates[0 kg ha^(-1)(low nitrogen,LN),240 kg ha^(-1)(normal nitrogen,NN),and 360 kg ha^(-1)(high nitrogen,HN)]in two wheat cultivars,Wennong 6(with a staygreen phenotype)and Jimai 20(with a non-staygreen phenotype).Flag leaf senescence was assessed using a Gompertz growth curve.Grain mass,dry matter accumulation and distribution,total N of flag leaf,and concentrations of zeatin riboside(ZR)and abscisic acid(ABA)were also used to evaluate the functional characteristics of flag leaves.Grain mass was negatively correlated with initial senescence rate(r_0)and duration of rapid chlorophyll loss(Chl_(loss)),whereas it was positively correlated with maximum senescence rate(r_(max)),average senescence rate(r_(aver)),persistence phase(Chl_(per)),total duration of flag leaf(Chl_(total))and inflection point cumulative temperature(M).Compared to Jimai 20,Wennong 6 had larger r_(aver),Chl_(per),and Chl_(total).The concentration of ZR was highest under the 6-BA×NN treatment,followed by the 6-BA×HN and 6-BA×LN treatments.However,the concentration of ABA showed the opposite trend.It was concluded that the staygreen phenotype Wennong 6 was associated with greater grain mass and altered cytokinin metabolism and could be classified as a functional staygreen type.Foliar application of 6-BA interacting with N at the NN level(240 kg ha^(-1))may be a beneficial strategy for improving grain yield of wheat by regulating endogenous hormones and the flag leaf senescence process.Increasing endogenous cytokinin promoted the transport of dry matter to grain.

Cytokinin induced shoot regeneration and flowering of Scoparia dulcis L.(Scrophulariaceae)-an ethnomedicinal herb

Objective:To develop an improved protocol for micropropagation of ethnomedicinally important Scoparia dulcis(S.dulcis) L.Methods:Explants were inoculated on MS basal medium supplemented with kinelin and 6-benzylaminopurine for shoot bud induction.To enhance the shoot induction,various auxins like 3-indoleacetic acid or 3-indolebutyric acid or a-naphthylacetic acid were tested along with 2.32 M KI and 4.44 μ M BAP.The regenerated shoots were rooted in half strength MS medium supplemented with various concentrations of IAA,IBA or NAA.After roots were developed,the plantlets were transplanted to pots filled with vermiculate and sand and kept in growth chamber with 70%-80%humidity under 16 h photoperiod.After acclimatization,the plantlets were transferred to the garden and survival percentage was calculated.Data were statistically analyzed and means were compared using Duncan's multiple range test(P<0.05).Results:An in vitro method was developed to induce high frequency shoots regeneration from stem,mature leaf and young leaf explants of S.dulcis.Shoot induction on young leaf explants was most successful in MS medium supplemented with combination of two cytokinins(2.32 μ M KI and 4.44 μ M BAP) 2.85 μ M IAA,10%CM and 1 483.79 μM adenine sulfate.A single young leaf explant was capable of producing 59 shoots after 13 days of culture. Flower was induced in medium supplemented with combination of KI and BAP.Conclusions: Cytokinins are the key factor to induce the direct shoot regeneration and flowering of S.dulcis.

Genome-wide identification and analysis of cytokinin dehydrogenase/oxidase(CKX) family genes in Brassica oleracea L.reveals their involvement in response to Plasmodiophora brassicae infections

Cytokinins are a class of phytohormones that promote cell division and differentiation and are thought to affect plant immunity to multiple pathogens.However,a comprehensive analysis of cytokinin dehydrogenase/oxidase(CKX)family genes in cabbage has not been reported.In this study,a total of 36 CKX genes were identified using a genome-wide search method.Phylogenetic analysis classified these genes into three groups.They were distributed unevenly across nine chromosomes in B.oleracea,and 15 of them did not contain any introns.The results of colinearity analysis showed that 36 CKX gene in Arabidopsis was present in several copies in the Brassica oleracea genome.An analysis of cisacting elements indicated that all genes possessed at least one stress or hormone responsive cis-acting element.A heatmap of CKX gene expression showed the patterns of expression of these genes in various tissues and organs.Three genes(Bol028363,Bol031036 and Bol018140)were relatively highly expressed in all of the investigated tissues under normal conditions,showing the expression profile of housekeeping genes.Generally,the expression patterns of CKX genes in Jingfeng 1 and Xiangan 336 were quite different under the same treatment.Notably,three genes(Bol020547,Bol028392 and Bol045724)were significantly down-regulated and up-regulated in the susceptible and resistant material,respectively,after inoculation,which may indicate their crucial roles in resistance to clubroot disease.The results provide insights for better understanding the roles of CKX genes in the B.oleracea–P.brassicae interaction.