The bHLH transcription factor CsPIF4 positively regulates high temperature-induced hypocotyl elongation in cucumber

High temperature-induced hypocotyl elongation is a typical thermomorphogenesis trait that may significantly affect early seedling growth and subsequent crop yield.The ambient temperature and endogenous auxin are two critical factors that regulate hypocotyl growth.However,the mechanism of temperature and auxin integration in horticultural plants remains poorly understood.In this study,the roles of the basic helix-loop-helix transcription factor CsPIF4 in regulating auxin biosynthesis genes and the auxin content in the hypocotyl of cucumber(Cucumis sativus L.)seedlings under high temperature were investigated.qRT-PCR and in situ hybridization analysis revealed that expression of CsPIF4 was enhanced in the epidermis and vascular bundles in the hypocotyl of cucumber seedlings in response to high temperature.qRT-PCR and HPLC analysis showed that CsPIF4 positively regulated transcription of the auxin biosynthesis gene CsYUC8 and the auxin content in the hypocotyl under high temperature(35℃).The CRISPR/Cas9-mediated knockout of CsPIF4 resulted in a shorter hypocotyl compared with that of the wild type,together with decreased expression of CsYUC8 and lower auxin content in response to high temperature.Furthermore,biochemical assays showed that CsPIF4 could bind directly to the G-box motif of the CsYUC8 promoter and thereby activate CsYUC8 expression.These findings provide insight into the molecular mechanism of high temperature-mediated hypocotyl elongation in cucumber.

Effects of Natural Brassinolide on Seed Germination and Hypocotyl Elongation of Beans

Seeds of soybeans and mung beans were soaked into five different concentrations （0, 0.05, 0.10, 0.20, 0.30 mg/L） of natural brassinolide （ NBR ） solution. According to the results, natural brassinolide treatment could improve seed germination rate and hypocotyl-radicle ratio of soybeans and mung beans and promote the growth of sprouts. To be specific, seed germination rate of soybeans reached the highest in 0.05 mg/L natural brassinolide treatment, which was im- proved by 25.0 percentage points compared with the control group, and the sprout length was improved by 4.33 em; 0.30 mg/L natural brassinolide exhibited the most significant promotion effect on seed germination and sprout growth of mung beans, seed germination rate was improved by 18.3 percentage points and sprout length was improved by 7.29 cm; hypocotyl-radiele ratio of soybean and mung bean sprouts reached the highest （2.96, 1.43 ） in 0.05 mg/L natural brassinolide treatment.

AFP2 Coordinates the Activity of PIF7 for Thermomorphogenesis in Arabidopsis Seedlings

Ambient temperature induces the hypocotyl elongation of seedling,called as thermomorphogenesis.It has been reported that the bHLH transcriptional factor PIF7 acts as the critical component to modulate plant thermomorphogenesis,but the underlying mechanism remains elusive.The phytohormone abscisic acid(ABA)suppresses the hypocotyl elongation under high temperature(HT)stress.As the ABI5 binding protein,AFP2 acts as the negative factor to control ABA signaling.In this study,we first identified AFP2 as the interaction protein of PIF7 in vitro and in vivo.Phenotype analysis revealed that overexpressing AFP2 reduced the hypocotyl elongation,while loss-of-function afp2 mutant showed longer hypocotyl under HT.Consistently,overexpressing AFP2 impaired the transactivation effect of PIF7 on auxin biosynthesis related genes YUC8 and IAA19,which possibly resulted into the shorter hypocotyl in the transgenic line overexpressing AFP2 or co-overexpressing AFP2 and PIF7.Thus,these data suggest that AFP2 suppressed PIF7 activity to suppress hypocotyl elongation.Furthermore,we found that HT gradually induced the degradation of AFP2 that possibly released the inhibitory effect of AFP2 on PIF7,thus induced hypocotyl elongation under HT.Taken together,our result reveals the novel function of AFP2 in coordinating thermomorphogenesis through sophistically modulating PIF7 activity.

Effect of Natural Brassinolide on Germination of Ailanthus altissima Seeds

The germination capacity of Ailanthus altissima seeds improved after the seeds were soaked with different concentrations of natural brassinolide （NBR）. The germination rate and germination energy of the seeds increased by 17.6% and 18.8%, and the mean germination speed （i.e., germination time） of the seeds was shortened by 1.4 d under the optimal concentration （0.4 mg·L^-1） treatment, compared with the control. After hypocotyls of A.altissima were treated with NBR, the elongation of the hypocotyls increased. Among different concentrations of the NBR, 0.4 mg·L^-1 NBR appeared to be the optimal concentration for the elongation of A.altissima hypocotyls.

The G-Protein β Subunit AGB1 Promotes Hypocotyl Elongation through Inhibiting Transcription Activation Function of BBX21 in Arabidopsis

Hypocotyl development in Arabidopsis thaliana is regulated by light and endogenous hormonal cues, mak- ing it an ideal model to study the interplay between light and endogenous growth regulators. BBX21, a B-box （BBX）-Iike zinc-finger transcription factor, integrates light and abscisic acid signals to regulate hypocotyl elongation in Arabidopsis. Heterotrimeric G-proteins are pivotal regulators of plant development. The short hypocotyl phenotype of the G-protein I^-subunit （AGB1） mutant （agbl-2） has been previously identified, but the precise role of AGB1 in hypocotyl elongation remains enigmatic. Here, we show that AGB1 directly interacts with BBX21, and the short hypocotyl phenotype of agbl-2 is partially suppressed in agb1-2bbx21-1 double mutant. BBX21 functions in the downstream of AGB1 and overexpression of BBX21 in agbl-2 causes a more pronounced reduction in hypocotyl length, indicating that AGB1 plays an oppositional role in relation to BBX21 during hypocotyl development. Furthermore, we demonstrate that the C-terminal region of BBX21 is important for both its intracellular localization and its transcriptional activation activity that is inhibited by interaction with AGB1. ChiP assays showed that BBX21 specifically associates with its own promoter and with those of BBX22, HY5, and GA2oxl. which is not altered in agbl-2. These data suggest that the AGB1-BBX21 interaction only affects the transcrip- tional activation activity of BBX21 but has no effect on its DNA binding ability. Taken together, our data demonstrate that AGB1 positively promotes hypocotyl elongation through repressing BBX21 activity.

Candidate genes conferring ethylene-response in cultivated peanuts determined by BSA-seq and fine-mapping

Ethylene plays essential roles in plant growth,development and stress responses.The ethylene signaling pathway and molecular mechanism have been studied extensively in Arabidopsis and rice but limited in peanuts.Here,we established a sand-culture method to screen pingyangmycin mutagenized peanut lines based on their specific response to ethylene(“triple response”).An ethylene-insensitive mutant,inhibition of peanut hypocotyl elongation 1(iph1),was identified that showed reduced sensitivity to ethylene in both hypocotyl elongation and root growth.Through bulked segregant analysis sequencing,a major gene related to iph1,named AhIPH1,was preliminarily mapped at the chromosome Arahy.01,and further narrowed to a 450-kb genomic region through substitution mapping strategy.A total of 7014 genes were differentially expressed among the ACC treatment through RNA-seq analysis,of which only the Arahy.5BLU0Q gene in the candidate mapping interval was differentially expressed between WT and mutant iph1.Integrating sequence variations,functional annotation and transcriptome analysis revealed that a predicated gene,Arahy.5BLU0Q,encoding SNF1 protein kinase,may be the candidate gene for AhIPH1.This gene contained two single-nucleotide polymorphisms at promoter region and was more highly expressed in iph1 than WT.Our findings reveal a novel ethylene-responsive gene,which provides a theoretical foundation and new genetic resources for the mechanism of ethylene signaling in peanuts.

The PRR-EC complex and SWR1 chromatin remodeling complex function cooperatively to repress nighttime hypocotyl elongation by modulating PIF4 expression in Arabidopsis

The circadian clock entrained by environmental light-dark cycles enables plants to fine-tune diurnal growth and developmental responses.Here,we show that physical interactions among evening clock components,including PSEUDO-RESPONSE REGULATOR 5(PRR5),TIMING OF CAB EXPRESSION 1(TOC1),and the Evening Complex(EC)component EARLY FLOWERING 3(ELF3),define a diurnal repressive chromatin structure specifically at the PHYTOCHROME-INTERACTING FACTOR 4(PIF4)locus in Arabidopsis.These three clock components act interdependently as well as independently to repress nighttime hypocotyl elongation,as hypocotyl elongation rate dramatically increased specifically at nighttime in the prr5-1 toc1-21 elf3-1 mutant,concomitantly with a substantial increase in PIF4 expression.Transcriptional repression of PIF4 by ELF3,PRR5,and TOC1 is mediated by the SWI2/SNF2-RELATED(SWR1)chromatin remodeling complex,which incorporates histone H2A.Z at thePIF4 locus,facilitating robust epigenetic suppression ofPIF4 during the evening.Overall,these findings demonstrate that the PRR-EC-SWR1 complex represses hypocotyl elongation at night through a distinctive chromatin domain covering PIF4 chromatin.

Clathrin light chains regulate hypocotyl elongation by affecting the polarization of the auxin transporter PIN3 in Arabidopsis

PIN-FORMED(PIN)-dependent directional auxin transport is crucial for plant development. Although the redistribution of auxin mediated by the polarization of PIN3 plays key roles in modulating hypocotyl cell expansion, how PIN3 becomes repolarized to the proper sites within hypocotyl cells is poorly understood. We previously generated the clathrin light chain clc2-1 clc3-1 double mutant in Arabidopsis thaliana and found that it has an elongated hypocotyl phenotype compared to the wild type. Here, we performed genetic, cell biology, and pharmacological analyses combined with live-cell imaging to elucidate the molecular mechanism underlying the role of clathrin light chains in hypocotyl elongation. Our analyses indicated that the defects of the double mutant enhanced auxin maxima in epidermal cells, thus, promoting hypocotyl elongation. PIN3 relocated to the lateral sides of hypocotyl endodermal cells in clc2-1 clc3-1 mutants to redirect auxin toward the epidermal cell layers.Moreover, the loss of function of PIN3 largely suppressed the long hypocotyl phenotype of the clc2-1 clc3-1 double mutant, as did treatment with auxin transport inhibitors. Based on these data, we propose that clathrin modulates PIN3 abundance and polarity to direct auxin flux and inhibit cell elongation in the hypocotyl, providing novel insights into the regulation of hypocotyl elongation.

Unraveling the Dynamic Integration of Auxin,Brassinosteroid and Gibberellin in Early Shade-Induced Hypocotyl Elongation

For shade-intolerant plants,a reduction in the red/far-red(R:FR)light ratio signals the close proximity of competitors and triggers shade-avoidance syndrome(SAS).Auxin,brassinosteroid,gibberellin and some transcriptional regulators have been reported to regulate shade-induced hypocotyl elongation.However,little is understood regarding the coordination of these multiple regulatory pathways.Here,combining time-lapse growth rates and transcriptomic data,we demonstrate that auxin and brassinosteroid affect two phases of shade-induced rapid growth,whereas gibberellin mainly contributes to the second rapid growth phase.PHYTOCHROME-INTERACTING FACTOR 7(PIF7)acts earlier than other PIFs.PIF4 and PIF5 modulate the second rapid growth phase.LONG HYPOCOTYL IN FAR-RED 1(HFR1)and PIF3-LIKE 1(PIL1)modulate two rapid growth phases.Our results reveal that hormonal and transcriptional regulatory programs act together to coordinate dynamic hypocotyl changes in an immediate response to a shade signal and provide a novel understanding of growth kinetics in a changing environment.

培养条件对甘蓝型黄籽油菜下胚轴的再生影响

以甘蓝型黄籽油菜GH01的下胚轴为材料,研究影响外植体芽再生的因素。试验结果表明,苗龄、预培养基的激素浓度和预培养时间、分化培养基等对芽再生频率均有较大影响。8d苗龄的下胚轴置 MS+1.5mg/L 2,4-D+0.1mg/L 6-BA培养基预培养4d后,转分化培养基MS+4.0mg/L 6-BA+0.05mg/L NAA+5.0mg/L AgNO_3+0.6mg/L GA_3 培养,可获得较高的芽再生频率。添加 5mng/L AgNO_3 处理可防止外植体褐化并有利于芽分化;0.6mg/L GA_3 处理可促进胚状体形成,提高芽再生频率。GH01 最高芽再生频率为40.50％。

铝胁迫对油菜种子萌发和幼苗生长的影响

以赣油杂1号和赣油杂2号油菜为材料,研究了不同浓度的铝处理对油菜种子萌发和幼苗生长的影响。结果表明,铝浸种降低了油菜种子的发芽率、发芽势、发芽指数、活力指数和植株鲜重。从铝处理抑制2个油菜根的伸长生长来看,赣油杂1号的耐铝性强于赣油杂2号且侧根较主根对铝处理反应更为敏感。

天然油菜素内酯对油松和刺槐种子发芽的影响

The germination capacity of Pinus tabulaeformis seeds was obviously improved after the seeds were soaked with the different concentrations of natural brassinolide. The germination rate and germination energy of the seeds were increased by 23 1% and 14 94% respectively, and the mean germination speed ( i.e. germination time) of the seeds was cut down by 1 day under the best concentration (0 05?mg·L -1 ) treatment, compared with the control. After Robinia pseudoacacia seeds were treated with the best concentration(0 1?mg·L -1 ) of natural brassinolide, the germination rate and germination energy of the seeds were increased by 10 9% and 15 9% respectively, and the mean germination speed of the seeds was cut down by 1 26 day, compared with the control. After hypocotyls of Pinus tabulaeformis and Robinia pseudoacacia were treated with the natural brassinolide, the elongation of their hypocotyls was obviously increased. 0 01?mg·L -1 concentration of the natural brassinolide was the most suitable for the elongation of Pinus tabulaeformis hypocotyls,and 0 005?mg·L -1 concentration was the best for the elongation of Robinia pseudoacacia hypocotyls.

天然油菜素内酯对五种牧草种子发芽和胚根下胚轴伸长的影响

用9个不同浓度的天然油菜素内酯溶液浸种处理5种牧草种子,观测其对种子发芽和胚根下胚轴伸长的影响。结果表明,0.01 mg/L浓度处理使苜蓿种子发芽率比对照提高了32.2%,发芽天数缩短了1.4 d;0.01mg/L处理使鲁梅克斯种子发芽率增加了27.8%,0.05 mg/L处理使其发芽天数提前了0.8 d;0.03 mg/L处理使普那菊苣种子发芽率提高了28.9%,发芽天数缩短了0.3 d;0.4 mg/L处理使串叶松香草种子发芽率增加了26.7%,发芽天数提前了1.2 d;0.03 mg/L处理使小冠花种子发芽率提高了23.3%,0.05 mg/L使其发芽天数缩短了0.9 d。0.05、0.07、0.03、0.4和0.03 mg/L处理对苜蓿、鲁梅克斯、普那菊苣、串叶松香草和小冠花胚根下胚轴伸长的促进效应最为明显。

水氮耦合对冬油菜氮营养指数和光能利用效率的影响

于2012—2013年和2013—2014年在冬油菜蕾薹期,设置3个施氮水平0、80、160 kg/hm2(分别记为N0、N1和N2)和3个灌溉水平0、60、120 mm(分别记为I0、I1和I2),探究蕾薹期不同灌溉、施氮量对冬油菜氮营养指数(NNI)、光能利用效率(RUE)、产量、水分利用效率(WUE)和氮肥偏生产力(NPFP)的影响。2 a田间试验结果表明,灌水且施氮能明显提高冬油菜地上部干物质量、光能利用效率和产量。I1N1处理的地上部干物质量比I1N2、I2N1和I2N2分别低0.80%、9.18%和11.12%。冬油菜在I0N1、I0N2、I2N1和I2N2处理下,均会出现氮素亏缺状况,不利于油菜生长;在I1N1和I1N2处理下,不同时期的NNI均大于1,I1N1的NNI在1附近波动,I1N2的NNI则远大于1,表明氮素过剩。2 a施氮和灌水处理对RUE的影响有显著的交互作用(P<0.05),I1N1无论在干旱年(2012—2013年)或降水量较多年份(2013—2014年)均能显著提高冬油菜的RUE,而过量灌溉或施氮对冬油菜RUE促进作用不明显,甚至有下降趋势。2 a灌溉和施氮处理对冬油菜籽粒产量、耗水量、WUE和NPFP影响的交互作用均达显著水平(P<0.05),2 a中灌水量为120 mm、施氮量为80 kg/hm2(I2N1)处理的产量最高,平均产量为3 385 kg/hm2,平均耗水量374 mm,平均WUE为9.1 kg/(hm2·mm),而2 a中灌水量为60 mm、施氮量为80 kg/hm2(I1N1)处理的WUE最高,其平均WUE比I2N1提高8.79%,平均耗水量减少42.5 mm,仅减产3.57%。从节水和生态可持续发展角度出发,灌水60 mm、施氮80 kg/hm2为冬油菜蕾薹期较优的灌溉施氮策略。

某些硫代甲基膦酸酯类化合物的植物生长调节活性的研究

本文报道本所最近合成的某些硫代甲基膦酸酯类化合物的植物生长调节活性。合成的８个化合物中，７个化合物具有明显的植物生长调节活性：１０ｐｐｍ处理后均明显促进黄瓜子叶扩张，１００ｐｐｍ处理后明显抑制小麦胚芽鞘伸长。本文以Ｓ－乙基Ｏ－（２－氯－４－溴苯基）甲基膦酸酯（下文称２号化合物）为代表重点报道其对黄瓜子叶扩张，叶绿素含量的促进作用及对油菜下胚轴伸长的抑制作用。

油菜转化体系中抗生素浓度的优化试验

以芥菜型油菜 (Brassicajuncea)DB3 下胚轴为外植体 ,对卡那霉素和羧苄青霉素对外植体分化影响进行了研究。结果表明卡那霉素不仅可以抑制芽的分化和愈伤的形成而且可以使分化出的芽在很短的时间内白化死亡 ,在浓度为 6 0mg/L时 ,四周后 ,可以使分化率为 0 ;羧苄青霉素在浓度为 0 .5 g/L时 ,可以完全抑制农杆菌的生长 。

二步培养和AgNO_3对甘蓝型油菜子叶和下胚轴芽再生的影响

以甘蓝型油菜（Brassica napus L．）品种浙双758为材料，研究二步培养及添加AgNO3对甘蓝型油菜子叶和下胚轴外植体离体再生的影响。外植体先在含0．5—1．5mg／L2，4-D的MS培养基上预培养3d或7d诱导愈伤组织的产生，再转到含有3mg／LBA和0．15mg／LNAA及添加或不添加2．5mg／LAgNO3的分化培养基上诱导芽的分化。结果表明，外植体愈伤组织诱导率和芽再生率与2，4-D浓度、预培养时间和AgNO3密切相关；分化培养基中添加银离子可显著增加不定芽的再生频率；二步培养及添加AgNO3可使半子叶、完整子叶和下胚轴外植体芽再生频率分别达到了96．1％，96．7％和96．7％。

天然油菜素内酯促进柠条和紫穗槐种子发芽及下胚轴伸长效应

用天然油菜素内酯处理后发现,与对照相比,0.05 mg/L浓度的处理使柠条种子发芽率和发芽势分别提高了23.2％和20.7％,0.1mg/L浓度使其平均发芽时间缩短了0.8 d;0.2mg/L浓度使紫穗槐种子发芽率和发芽势提高了11.4％和22.7％,平均发芽时间缩短了0.8d。天然油菜素内酯对柠条和紫穗槐下胚轴切段伸长也有明显促进作用,其中0.1mg/L浓度对柠条下胚轴伸长效应最佳,0.2 mg/L浓度促进紫穗槐下胚轴伸长效果最好。

光与IAA和NAA对拟南芥下胚轴伸长的影响

利用拟南芥(Arabidopsis thaliana)野生型(WT)及其光受体缺失突变体研究了光与IAA(吲哚乙酸)和NAA(α-萘乙酸)对拟南芥下胚轴伸长的影响。结果表明,白光及IAA和NAA都能独立抑制野生型拟南芥(Arabidopsis thaliana)幼苗下胚轴伸长。白光下,1 μmol/L和10 μmol/L的IAA对WT下胚轴伸长的抑制率显著大于黑暗下,但100 μmol/L的IAA对WT下胚轴伸长的抑制率却显著小于黑暗;白光下和黑暗下1 μmol/L的NAA对WT下胚轴伸长的抑制率无显著差异,白光下10 μmol/L和100 μmol/L的NAA对WT下胚轴伸长的抑制率显著小于黑暗;利用不同的光受体缺失突变体研究光受体的作用表明,隐花色素1、光敏色素A和光敏色素B参与调节了光对下胚轴的抑制作用。

质膜氧化还原系统在植物伸长生长中的作用

以大豆下胚轴切段为材料，研究了质膜氧化还原系统对其伸长生长的作用，结果表明，ＮＡＤＨ氧化酶活性与大豆下胚轴伸长生长相关性极显著（Ｒ＝０．９４，Ｐ＝０．０１），而ＮＡＤＨ－Ｆｅ（ＣＮ）３－６氧化还原酶活性与其相关性不显著。大豆下胚轴伸长生长最快的第一切段，其ＮＡＤＨ氧化酶活性最高。第一切段的伸长生长及ＮＡＤＨ氧化酶对ＩＡＡ均有明显的正负反应。ＩＡＡ促进ＮＡＤＨ氧化酶活性。