Gibberellin-induced inhibition and promotion of sprouting in aerial tubers of Begonia evansiana Andr. in relation to photoperiodic treatment and tuber stage

Gibberellic-acid (GA₃) treatment, when applied within a period ranging from the start of short-day (SD) treatment until about 10 SD, GA₃ strongly inhibited formation of aerial tubers in response to SD and brought about sprouting of developing aerial tubers. In contrast, when applied after about 10 SD or more, GA₃ hastened the completion of the dormant state in the tubers and prolonged their dormancy. The dormancy-promoting effect of GA₃ on detached tubers increased with their degree of maturation. Application of growth retardants N-dimethylaminosuccinamic acid (B-9), 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine carboxylate methyl chloride (AMO-1618) and 2-chloroethyltrimethylammonium chloride (CCC) to the cuttings delayed the onset of dormancy in the aerial tuber. When the retardants were applied to detached aerial tubers, however, such a delay of dormancy was not observed, and GA₃ application did not inhibit sprouting in aerial tubers detached from CCC-treated cuttings.Abbreviations GA gibberellin - GA₃ gibberellic acid - SD short day(s) - LD long day(s) - SDP short-day plant - LDP long-day plant - CCC 2-chloroethyltrimethylammonium chloride - B-9 N-dimethylaminosuccinamic acid - AMO-1618 2-isopropyl-4-dimethyl-amino-5-methylphenyl-1-piperidine carboxylate methyl chloride     

The effect of low temperature and GA3 treatments on dormancy breaking and activity of antioxidant enzymes in Fritillaria meleagris bulblets cultured in vitro

We investigated the effect of low temperature and gibberellic acid (GA₃) treatment on dormancy in Fritillaria meleagris L. bulbs. Also, we studied the effect of dormancy breaking on the antioxidant enzymes activity. To overcome dormancy, bulbs require a period (4–8 weeks) of exposure to low temperature. Bulbs regenerated in vitro were grown in the dark on medium without growth regulators at the standard (24 °C) or at low temperatures (4 and 15 °C) for 4, 6, 8 and 10 weeks. Bulbs were collected after 3, 4 and 5 weeks of cooling at 4 °C. To investigate the influence of GA₃ on dormancy, bulbs were treated for 24 h with GA₃ solutions with 1, 2 and 3 mg l^?1 concentrations. During the period of growth of bulbs at 4 °C, regeneration of bulbs was very weak, while at 15 °C the number of regenerated bulbs increased significantly. Improved bulb sprouting was achieved by a short treatment with gibberellin. Low temperature also represents a kind of oxidative stress for the plant. The activity of superoxide dismutase, catalase (CAT) and peroxidase (POX) in bulbs of F. meleagris L. grown in vitro and ex vitro increased with decreasing temperature in contrast to glutathione reductase. POX showed generally lower activity than CAT which indicates that major role in the breaking dormancy and preparing bulbs for sprouting have catalases.     

沙葱萤叶甲卵滞育的转录组学分析

【目的】建立沙葱萤叶甲Galeruca daurica滞育卵转录组数据库,挖掘卵滞育相关的基因以及代谢和信号通路,在转录组水平探讨卵滞育的分子机制。【方法】采用Illumina NovaSeq6000高通量测序平台对沙葱萤叶甲滞育卵与解除滞育卵进行转录组测序,并进行生物信息学分析;利用DESeq软件分析沙葱萤叶甲滞育卵与解除滞育卵中的差异表达基因,对差异表达基因进行KEGG通路富集分析;利用qRT PCR技术对10个差异表达基因的表达模式进行验证。【结果】基于沙葱萤叶甲滞育卵与解除滞育卵转录组测序结果,共获得53 389个unigene,其中差异表达基因2 145个,24个差异表达基因与保幼激素信号及脂肪酸生物合成和降解相关。与解除滞育卵相比,滞育卵转录组中1 297个基因上调表达,富集于124条KEGG通路,其中核糖体通路显著富集;848个基因下调表达,富集于73条KEGG通路,其中MAPK信号通路和糖胺聚糖生物合成通路显著富集。qRT-PCR结果表明,随机选取的10个差异表达基因的表达趋势与RNA-Seq转录组测序结果完全一致。【结论】保幼激素,脂肪酸生物合成和降解,核糖体,MAPK信号及糖胺聚糖生物合成等通路可能在沙葱萤叶甲卵滞育调控中起着重要的作用。     

乙烯利对苦瓜幼苗内源激素代谢及相关调控基因表达的影响

以苦瓜常规品种“绿爵士”为试材,在日光温室内于幼苗3～4叶期叶面喷施乙烯利溶液,通过高效液相色谱串联质谱(HPLC-MS/MS)仪测定了相关内源激素的含量,并结合高通量测序技术对相关调控基因表达进行分析,探究外源乙烯利对苦瓜幼苗激素代谢的影响,获得苦瓜应对外源乙烯诱导的内源激素代谢靶点,初步明确相关调控基因的作用特点,为深入开展苦瓜类作物外源乙烯调控机制的研究奠定基础。结果表明：(1)在外源乙烯利作用下,苦瓜幼苗植株内源乙烯合成直接前体物质1-氨基环丙基-1-羧酸(ACC)含量和主要限速酶ACC合成酶(ACS)活性均表现为显著升高的趋势;内源生长素(IAA)和细胞分裂素(tZR)的含量同样显著升高,而其赤霉素(GA₃)的含量则显著降低。(2)经过Hi-seq测序,共获得1 234个差异表达基因(DEGs),功能富集分析显示有570个DEGs富集于118条代谢通路中。(3)对所有DEGs进行功能注释,鉴定了多个参与内源激素合成及信号转导的基因,包括乙烯代谢相关的ACS、ACO、HMT3、EIN3、ERFs基因,IAA代谢相关的ALDH、TAA1、UGT74B1、AU...     

Identification of Endogenous Gibberellins in Dormant Bulbils of Chinese Yam, Dioscorea opposita

It is known that dormancy of the genus Dioscorea is induced by application of gibberellin (GA) A₃. To understand the role of GAs in dormancy induction, endogenous GAs have been identified by Kovats retention indices and full mass spectra from capillary gas chromatography-mass spectrometry analysis of purified extract from dormant bulbils of Dioscorea opposita Thunb. These include GA₄, GA₉, GA₁₂, GA₁₉, GA₂₀, GA₂₄, GA₃₆, and GA₅₃; their presence suggests the occurrence of two biosynthetic pathways in D. opposita bulbils, the early 13-hydroxylation pathway and the non-13-hydroxylation pathway.     

Implication of Ethylene in the Release of Secondary Dormancy in Amaranthus caudatus L. Seeds by Gibberellins or Cytokinin

Ethephon (Eth), gibberellin A₃, A_{4 + 7} (GA₃, GA_{4 + 7}), and 6-benzyladenine (BA) removed secondary dormancy of Amaranthus caudatus seeds. The GAs and BA potentiated the effect of ethephon or 1-aminocyclopropane-1-carboxylic acid (ACC), an ethylene biosynthesis precursor, in terms of the rate or final percent of germination. Aminoethoxyvinylglycine (AVG), an ACC synthase activity inhibitor, was observed to simultaneously inhibit the release from dormancy effected by GA₃ or BA as well as the ethylene production stimulated by these regulators. Breaking of secondary dormancy by GA₃, GA_{4 + 7} or BA was prevented by 2,5-norbornadiene (NBD), an inhibitor of ethylene binding. Ethylene completely or markedly reversed the inhibitory effect of NBD. We thus conclude that the removal of secondary dormancy in Amaranthus caudatus seeds by gibberellin or benzyladenine involves ethylene biosynthesis and action.     

Dormancy in Garlic (Allium sativum L.) cv. Rosado Paraguayo I. Levels of Growth Substances in "Seed Cloves" under Storage

The period of dormancy in "seed cloves" of garlic (Allium sativumL.) under storage was determined by measuring the growth ofthe "first foliar leaf" and its sprouting capacity. The endogenouscontents of growth inhibitors and gibberellins were also measuredby bioassays. Dormancy of garlic bulbs can be characterizedby lack of gibberellin and a presence of moderate contents ofgrowth inhibitors. (Received October 26, 1982; Accepted August 25, 1983)     

Possible control of gibberellin-induced release of temperature-dependent primary dormancy in seeds of celery (Apium graveolens L.) by transmembrane ion fluxes

The temperature-dependent primary dormancy of cv Florida 683 celery seeds in darkness was broken by GA_4/7 (2 × 10^-4 M) alone but other growth regulators such as BA, ethephon or daminozide were necessary to break dormancy of cv Lathom Blanching seeds in the presence of GA_4/7 at this concentration. Although AgNO₃ partially inhibited both the ethephon- and BA- induced germination of cv Lathom Blanching seeds in the presence of GA_4/7 in the dark it did not affect the promotive action of daminozide. Ethephon did not overcome the inhibitory action of high concentrations of AgNO₃ in the light. The ethylene synthesis inhibitor aminoethoxyvinylglycine (AVG) did not inhibit the germination of cv Lathom Blanching seeds induced by growth regulators in the dark or in the absence of growth regulators in the light. Fusicoccin (FC) did not break celery seed dormancy unless applied in the presence of GA_4/7. Germination of cv Lathom Blanching celery seeds treated with GA_4/7 at 16°C in the dark was inhibited by the K⁺ ionophore benzo-18-crown-C-6 (18-C-6) and in the presence of Ca²⁺ by the Ca²⁺ ionophore A23187; the 18-C-6 inhibition was reversed by BA.It is concluded that the involvement of gibberellin in celery seed dormancy is not dependent on endogenous ethylene and is directly or indirectly controlled through the action of other hormones on transmembrane ion fluxes.     

The Role of Growth Substances in the Regulation of Onion Bulb Dormancy

The correlation between sprouting and changes in endogenousgrowth substances was investigated in stored onion bulbs (Alliumcepa c.v. Rijnsburger and Lancastrian). In the main experimentsbulbs were removed from store at approximately fortnightly intervals,samples were assessed for percentage sprouting and non-sproutingbulbs were either extracted for hormone assay or treated withgrowth substances in an attempt to induce sprouting. In otherexperiments the hormone content of bulbs at different stagesof sprouting was assessed. Growth-inhibitor and gibberellinactivity decreased before sprouting, but there was an increasein gibberellin and auxin activity as sprouting commenced. Gibberellinactivity was highest in bulbs with well-developed sprouts whereasauxin activity occurred mainly in bulbs in which early sproutdevelopment was visible only on their being cut open. Therewas no conclusive evidence that bulb dormancy could be brokenby application of the gibberellins GA₃ and GA_4/7, or the auxin1-naphthylacetic acid (NAA). Maleic hydrazide (MH) completelyinhibited root and sprout development but the growth retardant(2-chloroethyl)trimethylammonium chloride (CCC) was mainly effectivein reducing root development and sprouting was only slightlyinhibited.     

Low temperature, gibberellin and acid lipase activity in removal of apple seed dormancy

The activity of acid lipase and the level of gibberellin A₄ (GA₄) were determined in apple embryos excised from seeds after different time periods of stratification and subsequently cultured in darkness at 4°C or at 25°C. Enzyme activity and GA₄ content were higher at 4°C. Exogenous gibberellin stimulated lipase activity, while AMO-1618, an inhibitor of gibberellin biosynthesis, inhibited, to the same degree, both the enzyme activity and the GA₄ accumulation. The involvement of GA₄ and lipolytic enzymes in cold-mediated removal of embryonal dormancy has been discussed and compared with the role of these two factors in light-stimulated germination of dormant apple embryos, described earlier (Smoleńska and Lewak 1974).     

Germination dimorphism in Suaeda acuminata: A new combination of dormancy types for heteromorphic seeds

Desert annual Suaeda acuminata produces two morphologically distinct types of seeds on the same plant. The main aims of our study were to compare germination characteristics of the dimorphic seeds, ascertain their dormancy types and give the hormonal explanation. The two seed types of S. acuminata absorbed water at different rates with brown seeds imbibing water faster. Germination percentages of brown seeds were significantly higher than those of black seeds in all temperature and light regimes tested. Eight weeks of cold stratification did not break dormancy of black seeds, whereas exogenous GA₃ promoted germination. Excised embryos of untreated black seeds produced normal seedlings. Contents of ZR, GA₃ and ABA of brown seeds were significantly higher than that of black seeds; while contents of IAA of black seeds were significantly higher than that of brown seeds. Brown seeds of S. acuminata are non-dormant, whereas black seeds have intermediate physiological dormancy (PD). Interaction among ZR, ABA and GA₃ may play an important role in dormancy status of both seed types. This is the first report of non-dormancy and intermediate PD in a heteromorphic species.     

Gibberellins and Subapical Cell Divisions in Relation to Bud Set and Bud Break in Salix pentandra

In young plants of Salix pentandra, a temperate zone deciduous woody species, elongation growth ceases and a terminal bud is formed at day lengths shorter than a critical length. This is the first step in dormancy development, making survival under harsh winter conditions possible. Early studies strongly indicate that gibberellin is involved in the photoperiodic control of bud set and bud break. GA₁ action was studied by application under short days to plants where cessation of shoot elongation had occurred, followed by subsequent anatomic investigations of shoot tips. Under short days the frequency of cell division decreased rapidly along with the earlier observed decrease in GA₁ levels. Application of GA₁ to short-day–induced terminal buds rapidly stimulated cell division in apices several days before visible shoot elongation in response to this treatment was observed. One day after GA₁ application a fourfold increase in cell division frequency in apices was observed, increasing to a maximum of sevenfold 2 days after application. Long-day treatment leading to induction of bud break after about 4–6 days was followed by slowly increasing frequency of cell divisions. In earlier studies of this species, short days and gibberellins had no effect on cell elongation. These data show that increased GA₁ content, by application or long-day treatment, results in increased frequency of mitosis. This strongly indicates that GA₁ affects stem elongation in connection with bud set and bud break primarily by affecting cell divisions in subapical tissues. Received February 26, 1999; accepted October 8, 1999     

三峡库区消落带野生狗牙根对水淹适生性的转录组分析

为探究狗牙根对水淹环境的适生性机制,取长势一致的狗牙根分为未水淹对照组(A1)和30 cm沉水处理组(A2),A2水淹15 d后两组同时采样,提取样本总RNA作转录组测序。A1和A2测序数据经de novo组装分别获得128031和83363条高质量Unigene;A1和A2对比发现28844条差异表达基因(differentially expressed genes, DEGs),其中11858条DEGs上调表达,16986条DEGs下调表达;功能注释显示,这些DEGs主要集中在转录、翻译、碳水化合物代谢和环境适应等途径;信号通路富集显示,包括植物对病原体的防御、物质代谢、光合作用、形态发育和抗氧化等过程的103个信号通路与狗牙根对水淹生境的适生性有关;随机挑选4个DEGs作qRT-PCR分析,荧光定量结果与测序数据基本一致,说明基于转录组分析DEGs的表达情况较为可靠。该工作或可为进一步挖掘与狗牙根水淹适生性相关的调控基因和功能基因提供基础。