Qualitative and Quantitative Analysis of Endogenous Gibberellins in Onion Plants and Their Effects on Bulb Development

Evidence has been reported that bulb development in onion plants (Allium cepa L.) is controlled by endogenous bulbing and anti-bulbing hormones, and that gibberellin (GA) is a candidate for anti-bulbing hormone (ABH). In this study, we identified a series of C-13-H GAs (GA₁₂, GA₁₅, GA₂₄, GA₉, GA₄, GA₃₄, and 3-epi-GA₄) and a series of C-13-OH GAs (GA₄₄, GA₂₀, GA₁ and GA₈) from the leaf sheaths including the lower part of leaf blades of onion plants (cv. Senshu-Chuko). These results suggested that two independent GA biosynthetic pathways, the early-non-hydroxylation pathway to GA₄ (active GA) and early-13-hydroxylation pathway to GA₁ (active GA), exist in onion plants. It was also suggested that GA₄ and GA₁ have almost the same ability to inhibit bulb development in onion plants induced by treatment with an inhibitor of GA biosynthesis, uniconazole-P. The endogenous levels of GA₁ and GA₄, and their direct precursors, GA₂₀ and GA₉, in leaf blades, leaf sheaths, and roots of 4-week-old bulbing and non-bulbing onion plants were measured by gas chromatography/selected ion monitoring with the corresponding [²H]labeled GAs as internal standards. In most cases, the GA levels in long-day (LD)-grown bulbing onion plants were higher than those of short-day (SD)-grown non-bulbing onion plants, but the GA₁ level in leaf blades of SD-grown onion plants was rather higher than that of LD-grown onion plants. Relationship between the endogenous GAs and bulb development in onion plants is discussed.     

Possible Involvement of Jasmonic Acid in Tuberization of Yam Plants

Jasmonic acid (JA) was isolated from yam leaves (Dioscorea batatas),with the guidance of assay for tuber-inducing activity whichwas carried out by cultures of single-node segments of potatostems in vitro, and identified by HPLC and mass spectrometry.The level of endogenous JA in the leaves of the plants, whichbeing 5 ? 10^–7 M at the first harvest, increased continuouslywith the growth of the plants. The effect of exogenous JA onthe tuberization of yam plants was examined in vitro, and itwas found to have strong tuber-inducing activity. The thresholdconcentration of JA for induction of yam tuberization was ca.10^–7M. These results suggest that tuberization of yamplants is controlled by JA. (Received February 25, 1991; Accepted April 15, 1991)     

茉莉酸生物合成的调控及其信号通路

茉莉酸类化合物作为一种细胞信号分子,在植物的生长发育、机械损伤、代谢调节及诱导防御相关基因表达等方面起着重要的作用。本文概述了茉莉酸的生物合成调控以及人们目前对茉莉酸信号通路的认识,并对该研究领域存在的问题及今后可能的研究方向进行展望。     

Regulation by Cytokinins of Endogenous Levels of Jasmonic and Salicylic Acids in Mechanically Wounded Tobacco Plants

Plants respond differentially to wounding and pathogens usingdistinct signaling pathways, so that wound signals are transmittedto jasmonic acid (JA) which induces basic pathogenesis-related(PR) proteins, whereas pathogenic signals cause, in additionto JA, accumulation of salicylic acid (SA) which stimulatesproduction of acidic PR proteins. Transgenic tobacco plantsexpressing a gene for a small GTP binding protein respond abnormallyto mechanical wounding to produce SA and consequently acidicPR proteins, suggesting that wound signals cross with pathogensignaling pathways [Sano et al. (1994) Proc. Natl. Acad. Sci.USA 91: 10556]. This unusual signal crossing is associated witha highly sensitive wound-response of transgenic plants which,upon wounding, produce JA at least eighteen hours earlier thanwild-type plants. When wildtype plants are wounded in the presenceof the synthetic cytokinin, benzylaminopurine, production ofJA begins six hours earlier than in untreated samples, and alsoSA begins to accumulate. The cytokinin antagonist, 2-chloro-4-cyclohexylamino-6-ethylamino-s-triazine,erases these effects. Because transgenic plants constitutivelyproduce four-to six-fold higher amounts of endogenous cytokininsthan wild-type plants, it is concluded that cytokinins are indispensablefor control of endogenous levels of SA and JA. (Received April 23, 1996; Accepted June 10, 1996)     

Qualitative and Quantitative Analysis of Endogenous Jasmonoids in Potato Plant (Solanum tuberosum L.)

Qualitative and quantitative analyses of endogenous jasmonoids were done by liquid chromatography/selected ion monitoring (LC-SIM) using deuterium-labeled compounds as internal standards. To prove the practicality of this way of analyzing the contents of endogenous jasmonoids in plants, the method was used for estimating jasmonoids in potato plants.     

Identification of Jasmonic Acid in Three Species of Higher Plants and Its Biological Activities

(–)-Jasmonic acid (JA) was isolated and characterizedfrom immature seeds of Phaseolus vulgaris L. as a growth inhibitoragainst rice seedlings. The presence of JA was also confirmedin both fresh leaves and insect galls of Castanea crenata Sieb.et Zucc. and immature seeds of Dolichos lablab L. by combinedgas chromatography-mass spectrometry analyses. The biologicalactivities of JA were evaluated in several bioassay systems,and it was shown that JA is a new type of plant growth regulator. (Received February 9, 1981; Accepted March 27, 1981)     

茉莉酸及其衍生物与植物有性生殖某些过程的关系

介绍茉莉酸(JA)及其衍生物与植物有性生殖某些过程的关系(JA及其衍生物在植物生殖器官中的分布以及它们与植物开花和植物有性生殖器官发育的关系),特别是它们对植物雄性器官发育影响的研究进展。     

碰伤富士苹果果实内源茉莉酸和主要保护酶活性的变化

以富士苹果为试验材料,采用自由落体将其从离地面40 cm和70 cm高处跌至大理石地面上,测定损伤后48 h内在室温贮藏条件下果实内源茉莉酸和主要保护酶活性的动态变化,探讨碰撞损伤对果实内源茉莉酸和主要保护酶活性的影响.结果显示:40 cm和70 cm高处摔伤两种处理的苹果果实的内源茉莉酸含量显著升高,乙烯释放速率、O(-)/(·)2产生速率和H2O2含量迅速增加,相应的保护酶(SOD、CAT、POD和PAL)活性也显著提高.研究表明,碰撞损伤后可以诱导富士苹果果实内源茉莉酸含量和乙烯释放速率迅速增加,以及主要保护酶活性提高,使活性氧代谢加强,并在一定程度上能引起苹果果实膜脂过氧化,进一步加重果实伤害.     

茉莉酸及其信号传导研究进展

茉莉酸及其衍生物茉莉酸甲酯等统称为茉莉酸盐,是广泛存在于植物中的一种生长调节物质,在植物细胞中起着非常重要的作用.茉莉酸作为信号分子广泛参与调节植物的生长发育和胁迫响应过程.本文主要就茉莉酸的生物合成、茉莉酸的信号传导途径和调控机制、茉莉酸的信号传导途径与乙烯、脱落酸、水杨酸和一氧化氮信号传导途径的相互关系进行了综述.     

茉莉酸信号转导突变体ber15的分离和基因克隆表明油菜素内酯的合成影响茉莉酸信号转导

bestatin是一种氨肽酶抑制剂,能够激活茉莉酸信号转导途径而诱导抗性相关基因的表达,从而为用化学遗传学手段解析茉莉酸途径提供了一个有效的工具。ber15是我们鉴定到的一个对bestatin不敏感的拟南芥突变体,随后的研究表明该突变体对外源茉莉酸的敏感性也明显降低,表明相应的野生型基因BER15在茉莉酸信号转导中起重要作用。图位克隆结果表明BER15编码一个细胞色素P450单加氧酶,是植物激素油菜素内酯合成途径中的一个关键酶。对BER15基因功能的深入研究将会为了解油菜素内酯的合成与茉莉酸信号途径间的互作关系提供证据。     

茉莉酸信号转导突变体ber15 的分离和基因克隆表明油菜素内酯的合成影响茉莉酸信号转导

bestatin是一种氨肽酶抑制剂, 能够激活茉莉酸信号转导途径而诱导抗性相关基因的表达, 从而为用化学遗传学手段解析茉莉酸途径提供了一个有效的工具。ber15是我们鉴定到的一个对bestatin不敏感的拟南芥突变体, 随后的研究表明该突变体对外源茉莉酸的敏感性也明显降低, 表明相应的野生型基因BER15在茉莉酸信号转导中起重要作用。图位克隆结果表明BER15编码一个细胞色素P450单加氧酶, 是植物激素油菜素内酯合成途径中的一个关键酶。对BER15基因功能的深入研究将会为了解油菜素内酯的合成与茉莉酸信号途径间的互作关系提供证据。     

Jasmonate-Inducible Genes Are Activated in Rice by Pathogen Attack without a Concomitant Increase in Endogenous Jasmonic Acid Levels

The possible role of the octadecanoid signaling pathway with jasmonic acid (JA) as the central component in defense-gene regulation of pathogen-attacked rice was studied. Rice (Oryza sativa L.) seedlings were treated with JA or inoculated with the rice blast fungus Magnaporthe grisea (Hebert) Barr., and gene-expression patterns were compared between the two treatments. JA application induced the accumulation of a number of pathogenesis-related (PR) gene products at the mRNA and protein levels, but pathogen attack did not enhance the levels of (-)-JA during the time required for PR gene expression. Pathogen-induced accumulation of PR1-like proteins was reduced in plants treated with tetcyclacis, a novel inhibitor of jasmonate biosynthesis. There was an additive and negative interaction between JA and an elicitor from M. grisea with respect to induction of PR1-like proteins and of an abundant JA-and wound-induced protein of 26 kD, respectively. Finally, activation of the octadecanoid signaling pathway and induction of a number of PR genes by exogenous application of JA did not confer local acquired resistance to rice. The data suggest that accumulation of nonconjugated (-)-JA is not necessary for induction of PR genes and that JA does not orchestrate localized defense responses in pathogen-attacked rice. Instead, JA appears to be embedded in a signaling network with another pathogen-induced pathway(s) and may be required at a certain minimal level for induction of some PR genes.     

Interplay Between Abscisic Acid and Jasmonic Acid and its Role in Water-oxidative Stress in Wild-type, ABA-deficient, JA-deficient, and Ascorbate-deficient Arabidopsis Plants

The interplay between jasmonic acid (JA) and abscisic acid (ABA) in plant responses to water stress and in water-stress-enhanced oxidative stress was investigated in Arabidopsis thaliana plants subjected to water stress by water deprivation. For this purpose a drought assay was conducted using Arabidopsis mutants impaired in ABA (aba2), JA (aos), and ascorbate (vtc1) biosynthesis. Our results show an interaction between ABA and JA during their biosynthesis. Moreover, the coordinated action of ABA and JA protected wild-type, aba2, and aos plants from the effects of stress. However, this effect was not observed in the vtc1 mutant, which showed a distinct decrease in the F _v/F _m ratio, concomitant with a marked fall in relative water content (RWC), despite high endogenous concentrations of JA and ABA. This finding indicates the relevance of ascorbate metabolism in plant acclimation to stress. Despite the interaction between the two phytohormones, drought-associated stomatal closure is regulated mainly by ABA and weakly by JA, whereas JA plays a role in the formation of antioxidants regulating ascorbate and glutathione metabolism. A time course analysis revealed the relevance of plant age and stress duration in the responses of the mutants compared to wild-type plants. Here we discuss the relationship between ABA, JA, ascorbate, and glutathione in plants under water stress.     

Analysis of Plant-Bacteria Interactions in Their Native Habitat: Bacterial Communities Associated with Wild Tobacco Are Independent of Endogenous Jasmonic Acid Levels and Developmental Stages

Jasmonic acid (JA) mediates defense responses against herbivores and necrotrophic pathogens but does it influence the recruitment of bacterial communities in the field? We conducted field and laboratory experiments with transformed Nicotiana attenuata plants deficient in jasmonate biosynthesis (irAOC) and empty vector controls (EV) to answer this question. Using both culture-dependent and independent techniques, we characterized root and leaf-associated bacterial communities over five developmental stages, from rosette through flowering of plants grown in their natural habitat. Based on the pyrosequencing results, alpha and beta diversity did not differ among EV and irAOC plants or over ontogeny, but some genera were more abundant in one of the genotypes. Furthermore, bacterial communities were significantly different among leaves and roots. Taxa isolated only from one or both plant genotypes and hence classified as ‘specialists’ and ‘generalists’ were used in laboratory tests to further evaluate the patterns observed from the field. The putative specialist taxa did not preferentially colonize the jasmonate-deficient genotype, or alter the plant''s elicited phytohormone signaling. We conclude that in N. attenuata, JA signaling does not have a major effect on structuring the bacterial communities and infer that colonization of plant tissues is mainly shaped by the local soil community in which the plant grows.     

The Role of Endogenous Abscisic Acid in the Response of Plants to Stress

When a continuous stream of warm air (38°C) was directedon to the leaves of dwarf bean seedlings they wilted and thengradually regained turgor. This process of adaptation was accompaniedby an increasing abscisic acid (ABA) level in the leaves andan increase in leaf resistance (R_L). It is suggested that theleaf-water deficit induced by the warm-air treatment causedthe increase in ABA level and that the latter was responsiblefor stimulating stomatal closure, enabling the plants to regainfull turgor. A similar type of adaptation, brought about byan increased level of ABA in the leaves, is believed to occurin tomato, dwarf bean, and wheat plants when they are flooded.Predictably, in rice, a species adapted to a flooded environment,seedlings showed no increase in ABA level as a result of flooding. It is proposed that adaptation may involve the formation ofan equilibrium between ABA and its conjugate form (i. e. theglucose ester). The ABA-conjugate was observed to disperse slowlyfrom leaves recovering from a water deficit and therefore itmay act as a metabolic ‘back-stop’, enabling the‘free’ ABA level to remain high for a period evenwhen the leaves have regained turgor. Abscisic acid appears to be responsible for alleviating theeffects of water stress in plants, making it possible for plantsto pass through periods of stress with little harm.     

在伤信号传导中茉莉酸与水杨酸的关系

近年来,发现茉莉酸和水杨酸都是植物体对外界伤害作出反应,表达抗性基因的信号分子。水杨酸可抑制茉莉酸类的合成及其所诱导的蛋白基因的表达;茉莉酸能阻止病原侵染后所产生的水杨酸的增加。茉莉酸信号转导途径和水杨酸信号转导途径存在着交叉,小GTP结合蛋白和细胞分裂素可能起着信号开关的作用。     

在伤信号传导中茉莉酸与水杨酸的关系

近年来,发现茉莉酸和水杨酸都是植物体对外界伤害作出反应,表达抗性基因的信号分子。水杨酸可抑制茉莉酸类的合成及其所诱导的蛋白基因的表达;茉莉酸能阻止病原侵染后所产缮乃钏岬脑黾印＼岳蛩嵝藕抛纪揪逗退钏嵝藕抛纪揪洞嬖谧沤徊妫。牵裕薪岷蛋白和细胞分裂素可能起着信号开关的作用。