为探究七叶一枝花的种子萌发生理机制,该文从种胚形态上对七叶一枝花种子萌发过程的时期进行了划分,并分析了不同时期种子内源激素含量及相关酶活性的变化规律.结果表明:(1)根据种胚形态可将种子萌发过程细分为 8 个时期,即种胚未萌动时期(S1 期)、心形胚时期(S2 期)、种胚膨大时期(S3 期)、胚根未突破种皮时期(S4 期)、子叶柄伸长和胚根突破种皮时期(S5 期)、下胚轴突破种皮时期(S6 期)、上胚轴伸长时期(S7 期)、胚根伸长时期(S8 期).(2)不同萌发时期种子的α-淀粉酶活性均明显高于β-淀粉酶.(3)超氧化物歧化酶(SOD)活性在S5 期最高,S1 期最低;过氧化物酶(POD)和过氧化氢酶(CAT)活性随种子萌发进程总体呈上升趋势,可溶性蛋白含量随种子萌发进程先下降后升高.(4)吲哚乙酸(IAA)、赤霉素(GA3)、脱落酸(ABA)和水杨酸(SA)含量随种子萌发进程整体呈下降趋势;1-氨基环丙烷羧酸(ACC)、茉莉酸(JA)、油菜素内酯(BRs)随种子萌发进程整体呈上升趋势;细胞分裂素类(CTKs)含量无显著变化;IAA/ABA和GA3/ABA随种子萌发进程呈先下降后上升趋势,而 CTKs/ABA 则不断升高.(5)ABA、IAA、GA3含量与胚率呈负相关,而ACC、JA、BRs、POD、CAT、β-淀粉酶活性与胚率呈正相关.综上认为,七叶一枝花在不同时期种子内源激素含量及相关酶活性各不相同,其中α-淀粉酶活性、POD活性可能与种胚胚根伸长有关,GA3可能影响种胚形成,而ABA则可能抑制种胚的生长发育.

Plant growth and development are intricately regulated by hor-mones such as auxins,gibberellins,jamonates,cytokinins,and brassinosteroids(BRs).BRs are a group of plant steroid hor-mones that play a vital role in plant growth and response to the environment.

Cytokinins influence many aspects of plant growth and development.Although cytokinin biosynthesis and signaling have been well studied in planta,little is known about the regulatory effects of epigenetic mod-ifications on the cytokinin response.Here,we reveal that mutations to Morf Related Gene(MRG)proteins MRG1/MRG2,which are readers of trimethylated histone H3 lysine 4 and lysine 36(H3K4me3 and H3K36me3),result in cytokinin hyposensitivity during various developmental processes,including callus induction and root and seedling growth inhibition.Similar to the mrg1 mrg2 mutant,plants with a defective AtTCP14,which belongs to the TEOSINTE BRANCHED,CYCLOIDEA,AND PROLIFERATING CELL FACTOR(TCP)transcription factor family,are insensitive to cytokinin.Furthermore,the transcription of several genes related to cytokinin signaling pathway is altered.Specifically,the expression of Arabidopsis thaliana HISTIDINE-CONTAINING PHOSPHOTRANSMITTER PROTEIN 2(AHP2)decreases significantly in the mrg1 mrg2 and tcp14-2 mutants.We also confirm the interaction between MRG2 and TCP14 in vitro and in vivo.Thus,MRG2 and TCP14 can be recruited to AHP2 after recognizing H3K4me3/H3K36me3 markers and promote the histone-4 lysine-5 acetylation to further enhance AHP2 expression.In summary,our research elucidate a previously unknown mechanism mediating the effects of MRG proteins on the magnitude of the cytokinin response.

叶片是植物重要的营养器官,叶缘锯齿(裂刻)在生产实践中有多种优势,叶缘锯齿调控研究对作物育种、生产实践具有指导意义.本文梳理了叶缘锯齿形成的调控机制,植物激素、基因表达、miRNA等协同作用调控叶缘锯齿形成.生长素(Auxin)在叶缘的不平衡积累能促进锯齿产生,细胞分裂素(CK,cytokinins)依赖Auxin在叶缘的积累促进叶形复杂度,而赤霉素(GA,gibberellin)负调控叶形复杂度.归纳了植物激素与基因参与叶缘锯齿形成的3条主要作用通路:TCP-CUC-PIN1-Auxin、KNOX-GA/CK、LMIl-CK.miR164、miR319、polycomb group表观遗传修饰和a-1,2糖基转移酶等也参与叶缘锯齿形成.研究表明环境因子温度和光强通过KNOX-GA通路调控叶片发育,高温和低光强均能降低叶形复杂度.不同植物控制叶缘锯齿性状的遗传机制存在较大差异.叶缘锯齿相关基因发掘以经济作物研究较多,未来果树育种应着手推进赏食兼用研究.

Several herbivorous insects and plant-associated microorganisms control the phytohormonal balance,thus enabling them to successfully exploit the plant by inhibiting plant defenses and withdrawing plant resources for their own benefit.The leaf-mining moth Phyllonorycter blancardella modifies the cytokinin (CK) profile of mined leaf-tissues,and the insect symbiotic bacteria Wolbachia is involved in the plant manipulation to the benefit of the insect host.To gain a deeper understanding into the possible origin and dynamics of CKs,we conducted an extensive characterization of CKs in larvae and in infected apple leaves.Our results show the enhanced CK levels in mines,both on green and yellow leaves,allowing insects to control their nutritional supply under fluctuating environmental conditions.The spatial distribution of CKs within the mined leaves shows that hormone manipulation is strictly limited to the mine suggesting the absence of CK translocation from distant leaf areas toward the insect feeding site.Mass spectrometry analyses reveal that major CK types accumulating in mines and larvae are similar to what is observed for most gall-inducers,suggesting that strategies underlying the plant manipulation may be shared between herbivorous insects with distinct life histories.Results further show that CKs are detected in the highest levels in larvae,reinforcing our hypothesis that CKs accumulating in the mines originate from the insect itself.Presence of bacteriaspecific methylthio-CKs is consistent with previous results suggesting that insect bacterial symbionts contribute to the observed phenotype.Our study provides key findings toward the understanding of molecular mechanisms underlying this intricate plant-insect-microbe interaction.

水稻是我国最主要的粮食作物,在国民经济和生活中占据重要地位.在水稻的周年生产中,病虫害的控制最为关键.因此,了解水稻与病虫害的互作机理,对水稻的育种和生产具有重要指导意义.植物激素是在植物生命活动中必不可少,调控植物生长、发育、衰老等主要生理过程的一类有机分子.近年来,大量实验证据表明,在植物与病原物互作过程中,植物内源激素也发挥着重要作用.随着水稻抗病和感病的机理解析越来越多,有关植物激素所扮演的重要功能角色也愈发清晰.其中,水杨酸、茉莉酸和乙烯研究最为广泛,它们之间的相互拮抗或协同效应决定了植物对病原物的防御反应强度.其它激素如:油菜素内酯、赤霉素、生长素、细胞分裂素、脱落酸等,单独或者通过调控水杨酸、茉莉酸和乙烯信号分子转导网络也参与植物与病原物互作过程.本研究综述了各大植物激素在水稻抗病或感病中作用,并对其未来研究进行展望,以便为水稻病害的防治提供理论依据.

Studies on natural variation are an important tool to unravel the genetic basis of quantitative traits in plants. Despite the significant roles of phytohormones in plant development,including root architecture,hardly any studies have been done to investigate natural variation in endogenous hormone levels in plants.Therefore,in the present study a range of hormones were quantified in root extracts of thirteen Arabidopsis thaliana accessions using a ultra performance liquid chromatography triple quadrupole mass spectrometer. Root system architecture of the set of accessions was quantified, using a new parameter (mature root unit) for complex root systems,and correlated with the phytohormone data.Significant variations in phytohormone levels among the accessions were detected,but were remarkably small,namely less than three-fold difference between extremes. For cytokinins,relatively larger variations were found for ribosides and glucosides, as compared to the free bases. For root phenotyping, length-related traits—lateral root length and total root length—showed larger variations than lateral root number-related ones. For root architecture, antagonistic interactions between hormones,for example,indole-3-acetic acid to trans-zeatin were detected in correlation analysis. These findings provide conclusive evidence for the presence of natural variation in phytohormone levels in Arabidopsis roots, suggesting that quantitative genetic analyses are feasible.

试验采用RACE技术克隆了团头鲂( Megalobrama amblycephala)G蛋白偶联受体43(GPR43)基因的cDNA序列,并探究了不同组织中的GPR43 mRNA表达量及黄连素对其表达量的影响.结果显示,克隆得到的团头鲂GPR43基因的cDNA序列全长为2026 bp, 含有1个长度为 981 bp的开放阅读框, 编码了326个氨基酸.RT-PCR检测发现GPR43在团头鲂的肠道、肌肉、鳃和肝胰腺中具有较高的表达.为期8周的养殖试验选取均重为(80.00±0.90) g的团头鲂320尾, 随机分于16个网箱中, 饲喂4种不同的试验日粮, 分别为正常日粮(脂肪含量为5%)、正常日粮+50 mg/kg黄连素、高脂日粮(脂肪含量为10%)、高脂日粮+50 mg/kg黄连素.结果显示:在肠道组织中,与正常日粮组相比,高脂组的GPR43表达量降低,添加黄连素能够显著升高其表达水平(P＜0.05).与正常日粮组相比, 高脂组的胆固醇(CHO)含量以及细胞分裂素蛋白激酶(p38)的表达量均呈现了显著上升(P＜0.05)的趋势, 添加黄连素后其含量及表达量显著下降(P＜0.05).肝胰腺组织和肌肉组织中的多不饱和脂肪酸(PUFA)含量变化也有着相似的趋势, 而肉碱棕榈酰基转移酶Ⅰ(CPT Ⅰ)、过氧化物酶体增值因子α&β (PPARα&β)、AMP依赖性蛋白激酶(AMPK)的表达量以及2个组织中的饱和脂肪酸(SFA)和单不饱和脂肪酸(MUFA)含量呈现出了相反的趋势.此外, 在正常日粮中添加黄连素并不能对上述各指标产生明显的调控效应,有时反而会导致轻微的负调控效应.综上结果表明,黄连素能够显著上调GPR43在高脂抑制下的表达量, 同时能够缓解高脂诱导的团头鲂肝胰腺脂肪沉积, 改善其脂肪代谢性能.黄连素对于脂肪代谢的调控作用可能通过GPR43受体来实现.

The phenomenon of plant root tips sensing moisture gradient in soil and growing towards higher water potential is designated as root hydrotropism,which is critical for plants to survive when water is a limited factor.Molecular mechanisms regulating such a fundamental process,however,are largely unknown.Here we report our identification that cytokinins are key signaling molecules directing root growth orientation in a hydrostimulation (moisture gradient) condition.Lower water potential side of the root tip shows more cytokinin response relative to the higher water potential side.Consequently,two cytokinin downstream type-A response regulators,ARR16 and ARR17,were found to be up-regulated at the lower water potential side,causing increased cell division in the meristem zone,which allows the root to bend towards higher water potential side.Genetic analyses indicated that various cytokinin biosynthesis and signaling mutants,including the arr16 arr17 double mutant,are significantly less responsive to hydrostimulation.Consistently,treatments with chemical inhibitors interfering with either cytokinin biosynthesis or cell division completely abolished root hydrotropic response.Asymmetrically induced expression of ARR16 or ARR17 effectively led to root bending in both wild-type and miz1,a previously known hydrotropism-defective mutant.These data demonstrate that asymmetric cytokinin distribution is a primary determinant governing root hydrotropism.