Regulation of potato meristem development by jasmonic acid in vitro

The influence of jasmonic acid (JA) on differentiation of meristems of the potato,Solanum tuberosum cv. Vesna, was investigated in vitro. Meristems were grown on Murashige and Skoog (MS) medium supplemented with indole-3-acetic acid (IAA) (10 M), kinetin (10 M), gibberellic acid (3 M), as modified by Bang. Addition of JA in concentrations of 0.5–10 M increased the number of meristems that developed into buds, particularly in meristems isolated from shoots grown from tubers in the dark. JA had no noticeable effect on meristems from germs grown in light. All added concentrations of JA retarded callus and root formation. The inhibitory effect on rhizogenesis disappeared immediately after transfer of the developed buds to medium without JA.     

Exogenously applied jasmonic acid induces changes in apical meristem morphology of potato stolons

Hooked apex stolons and initial swelling stolons of potato plants were treated with 3 x 10-8 mol l-1 jasmonic acid (JA) to study the effect of this compound on histology, cell expansion and tissue differentiation. In hooked apex stolons, JA application increased the meristem thickness and reduced the length of the leaf primordia, whereas in initial swelling stolons narrowing of the apical region, absence of leaf primordia and swelling of the subapical meristem were evident. Early vascular tissue differentiation was observed in response to JA treatment, especially of xylem elements from regions proximal to the tunic. Protoxylem elements, such as tracheal elements, were present with thin primary cell walls. The cell area was measured in two zones: zone I, central mother cells situated immediately under the tunic; and zone II, rib meristem cells. JA caused a four- and six-fold increase in cell area in both zones in hooked apex stolons and initial swelling stolons, respectively. Thus, tuber formation is concluded to occur as a consequence of increased cell expansion, a reduction in the length of leaf primordia, enlargement of meristems, and early vascular tissue differentiation.     

Effect of jasmonic acid on in vitro explant growth and microtuberization in potato

The shoot fresh mass, root length and root numbers of two potato (Solanum tuberosum L.) cultivars Favorita and Helanwuhua were increased significantly by the application of 0.2 – 2 mg dm⁻³ jasmonic acid (JA) in the Murashige and Skoog medium. However, the growth of potato explants was inhibited by JA at high concentrations (20 – 50 mg dm⁻³). Chlorophyll content in explant leaves decreased with an increase in the concentration of JA. In leaves treated with 0.2 mg dm⁻³ JA acid peroxidase activity increased, while in the leaves treated with more than 2 mg dm⁻³ JA peroxidase activity decreased. Under the dark, the microtuber numbers, fresh mass and percentage of big microtubers of two potato cultivars were not promoted by the application of 0.2 – 50 mg dm⁻³ JA.     

Changes in the plastid apparatus of apical meristem cells of potato tubers upon growth regulation with jasmonic acid

A comparative ultramorphometric study of the effect of jasmonic acid (JA) on the plastid apparatus in apical cells of potato tubers varying in physiological state was performed. When tubers were treated with JA at forced rest, the plastid apparatus of apical cells decreased in area and plastid proliferation was suppressed. When treatment was performed during growth, the area of the plastid apparatus remained unchanged, division was suppressed, and plastid budding was stimulated in apical cells. There was also a common response to JA that was independent of the physiological state of tubers. JA stimulated the development of the internal membrane system in plastids, reduced the amount of protein inclusions, and increased the portion of plastids having cisterns of the granular endoplasmic reticulum (GER) around their envelopes. The ultrastructural changes in plastids made it possible to assume that JA increases the biosynthetic activity of the plastid apparatus in apical meristem cells of potato tubers.     

Phospholipid and phospholipase changes by jasmonic acid during stolon to tuber transition of potato

Potato tuber formation starts with the stolon swelling and is regulated by jasmonates. The cascade of events leading to tuber formation is not completely understood. The aim of this study was to evaluate phospholipid composition and phospholipase activities during four stages of stolon-to-tuber transition of Solanum tuberosum L., cv. Spunta, and involvement of phosphatidic acid (PA) in stolon cell expansion during early stages. Effects of jasmonic acid (JA) treatment on phospholipid content and activation of phospholipase D (PLD) (EC 3.1.4.4) and phosphatidylinositol-4,5-bisphosphate-specific phospholipase C (PIP₂-PLC) (EC 3.1.4.3) were studied in the early stages (first stage, hooked apex stolon; second stage, initial swelling stolon) of tuberization. All the phospholipid species identified, phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), PA, and cardiolipin (CL), decreased as tuber formation progressed. PLD and PLC were activated in control tissues at an early stage. JA treatment caused a decrease of PC and PS in first stage stolons, accumulation of PA in second stage stolons, and modification of PLD and PLC activities. PA increased stolon cell area in the first and second stages. These findings indicate that phospholipid catabolism is activated from the early stages of tuber formation, and that JA treatment modifies the pattern of phospholipid (PC, PS, and PA) composition and phospholipase (PLD and PLC) activity. These phospholipids therefore may play a role in activation of an intracellular mechanism that switches the developmental fate of stolon meristem cells, causing differentiation into a tuber.     

Sucrose and jasmonic acid interact in photosynthetic pigment metabolism and development of potato (Solanum tuberosum L. cv. Sante) grown in vitro

Potato (Solanum tuberosum L., cv. Sante) plantlets grown from stem node culture on medium supplemented with 90 mM sucrose accumulated lower amounts of photosynthetic pigments per mg dry weight in comparison to those grown on 30 mM sucrose. Addition of 0.1, 1 or 10 µM jasmonic acid (JA) to the medium resulted in a decrease of chlorophylls and carotenoids in the plantlets grown on either sucrose concentration. JA treatment induced de-epoxidation of violaxanthin to antheraxanthin and zeaxanthin only in those plantlets grown on a higher amount of sucrose in which hyperhydric symptoms were observed. The synergistic effect of JA and sucrose was clearly demonstrated in the plantlets grown on 90 mM sucrose and 1 µM JA. This was possibly due to overaccumulation of sucrose, the consequence of the most developed root system, and/or to stimulated water and solute transport by other mechanisms.     

Stimulatory effects of jasmonic acid on potato stem node and protoplast culture

The effect of jasmonic acid (JA), in a wide range of concentrations (0.01–100 M), on the development of potato plantlets (Solanum tuberosum L.cv. Vesna) was investigated in order to discriminate between physiological and supraoptimal effects of this growth regulator in vitro. Concentrations from 0.1–1 M significantly increased the length of developed plants. Application of JA in these concentrations resulted in a very well differentiated root system with many lateral branches. With increasing JA concentrations, the main roots shortened and thickened. Concentrations higher than 10 M led to the compaction of the stem, roots, and root hairs, giving a stunted appearance to the plants. The effect of JA on cell wall regeneration and callus formation was observed in potato leaf protoplast culture. JA at concentrations from 0.01–1 M stimulated cell division and microcalli development.     

Overexpression of jasmonic acid carboxyl methyltransferase increases tuber yield and size in transgenic potato

Jasmonates control diverse plant developmental processes, such as seed germination, flower, fruit and seed development, senescence and tuberization in potato. To understand the role of methyl jasmonate (MeJA) in potato tuberization, the Arabidopsis JMT gene encoding jasmonic acid carboxyl methyltransferase was constitutively overexpressed in transgenic potato plants. Increases in tuber yield and size as well as in vitro tuberization frequency were observed in transgenic plants. These were correlated with JMT mRNA level––the higher expression level, the higher the tuber yield and size. The levels of jasmonic acid (JA), MeJA and tuberonic acid (TA) were also higher than those in control plants. Transgenic plants also exhibited higher expression of jasmonate-responsive genes such as those for allene oxide cyclase (AOC) and proteinase inhibitor II (PINII). These results indicate that JMT overexpression induces jasmonate biosynthesis genes and thus JA and TA pools in transgenic potatoes. This results in enhanced tuber yield and size in transgenic potato plants.     

Regulation of extent of vegetative development of the maize shoot meristem

In maize plants ( Zea mays L.), the extent of vegetative development in the shoot is precisely regulated such that the apical meristem produces a predictable number of leaves before converting to tassel development. In previous experiments using shoot apex culture, we showed that the developmental program that limits vegetative development in maize is not intrinsic to the shoot apical meristem. Rather, the meristem receives information from elsewhere in the plant and responds by either continuing leaf initiation or becoming determined for determinate growth and forming an inflorescence, the tassel. Here we examine leaf primordia as potential sources for that information using shoot apex culture. Our results show that the presence of the four to six youngest leaf primordia on the shoot apex is sufficient to provide such information. The ability to reset shoot development by meristem culture also allows us to examine the basis for expression of a specific phenotype at a particular developmental stage. We found that the mutation hcf106 , which is typically expressed only during seedling stages, is not re-expressed when the shoot morphogically has regained a juvenile phase.     

Changes in jasmonic acid concentration during early development of apple fruit

Apple fruits ( Malus domestica Borkh.) were harvested from 24 to 136 days after full bloom (DAFB) and endogenous jasmonic acid was analyzed by GC-MS. There were two isomers of jasmonic acid in apple fruit with a ratio of 37:63 ( cis:trans ). The cis:trans ratio remained relatively constant throughout this period of fruit development. The endogenous jasmonic acid concentration was 138 ng g⁻¹ fresh weight 24 DAFB and decreased as fruit developed. Changes in jasmonic acid concentration were coincident with those of respiration, ethylene production, and anthocyanin accumulation in patterns consistent with the reported responses to exogenous jasmonates. Possible roles for jasmonic acid during early fruit development are discussed.     

茉莉酸诱导番茄对烟粉虱发育、存活与繁殖的影响

【背景】目前,烟粉虱已成为世界性的入侵害虫,对我国的农业生产造成了严重损失。由于烟粉虱抗药性增长迅速,以非化学防治为主的综合防治措施,成为控制烟粉虱的重要手段。近年来,茉莉酸作为与损伤相关的植物激素和信号分子,已被发现广泛存在于植物体内,外施茉莉酸可激活植物的防御系统,诱导其产生次生防御物质,从而影响包括烟粉虱在内的多种害虫的生长发育、繁殖与存活等。【方法】在温度（26±1）℃、相对湿度（75±5）％、光照L：D=14：10的条件下,通过在番茄根部和叶部外施茉莉酸,研究茉莉酸诱导的番茄上烟粉虱的生长发育和繁殖等生物学特性。【结果】在茉莉酸诱导的番茄上,烟粉虱的发育历期以叶部诱导（shootJA．induced,SJA）的番茄上最长,平均历期为27．3d,与对照组（control,CON）番茄上的25．7d和根部诱导（root JA-induced,RJA）番茄上的25．8d差异显著;在SJA和CON番茄上,烟粉虱的世代存活率分别为47．17％和55．57％,而在RJA番茄上烟粉虱的存活率为81．13％,后者与前两者差异达到显著水平;烟粉虱成虫在CON、RJA和SJA番茄上的平均寿命分别为25．1、23．6和18．7d,即在JA诱导的番茄上烟粉虱成虫的平均寿命明显缩短;在产卵量方面,对照番茄上发育的烟粉虱平均单雌产卵量最大,为132．8粒,SJA番茄上发育的烟粉虱平均单雌产卵量最小,为107．9粒,两者差异显著;RJA番茄上发育的烟粉虱平均单雌产卵量为118．1粒,与前两者无显著差异。【结论与意义】利用茉莉酸诱导番茄可对烟粉虱的发育、繁殖和存活产生不同程度的影响,且诱导部位不同产生的影响也有很大差异。本结果对探索烟粉虱等刺吸式害虫的防治新策略有一定的参考价值。     

Abscisic acid and jasmonic acid activate wound-inducible genes in potato through separate, organ-specific signal transduction pathways

Mechanical damage to leaf tissue causes an increase in abscisic acid (ABA) which in turn activates the biosynthesis of jasmonic acid (JA). The resulting higher endogenous JA levels subsequently activate the expression of wound-inducible genes. This study shows that JA induces the expression of different sets of genes in roots and leaves of potato plants. When roots of intact plants were treated with JA, high levels of proteinase inhibitor II (pin2), cathepsin D inhibitor, leucine aminopeptidase and threonine deaminase mRNAs accumulated in the systemic leaves. However, in the treated roots, very low, if any, expression of these genes could be detected. In contrast, a novel, root-specific pin2 homologue accumulated in the JA-treated root tissue which could not be detected in leaves, either systemic or those directly treated with JA. Application of okadaic acid and staurosporine revealed that a protein phosphorylation step is involved in the regulation of this differential response. In leaves, a protein phosphatase is required for the JA-induced expression of pin2 and the other genes analysed. This phosphatase activity is not necessary for the JA-induced expression of a pin2 homologue in roots, suggesting the existence of different transduction pathways for the JA signal in these organs. The requirement of a protein phosphatase activity for JA-mediated gene induction has enabled identification of a JA-independent pathway for ABA induction of pin2 and the other wound-inducible genes. This alternative pathway involves a protein kinase, and appears to be selective for wound-inducible genes. Our data suggest the presence of a complex, organ-specific transduction network for regulating the effects of the plant hormones ABA and JA on gene expression upon wounding.     

Suppression of a vegetative MADS box gene of potato activates axillary meristem development

Potato MADS box 1 (POTM1) is a member of the SQUAMOSA-like family of plant MADS box genes isolated from an early stage tuber cDNA library. The RNA of POTM1 is most abundant in vegetative meristems of potato (Solanum tuberosum), accumulating specifically in the tunica and corpus layers of the meristem, the procambium, the lamina of new leaves, and newly formed axillary meristems. Transgenic lines with reduced levels of POTM1 mRNA exhibited decreased apical dominance accompanied by a compact growth habit and a reduction in leaf size. Suppression lines produced truncated shoot clusters from stem buds and, in a model system, exhibited enhanced axillary bud growth instead of producing a tuber. This enhanced axillary bud growth was not the result of increased axillary bud formation. Tuber yields were reduced and rooting of cuttings was strongly inhibited in POTM1 suppression lines. Both starch accumulation and the activation of cell division occurred in specific regions of the vegetative meristems of the POTM1 transgenic lines. Cytokinin levels in axillary buds of a transgenic suppression line increased 2- to 3-fold. These results imply that POTM1 mediates the control of axillary bud development by regulating cell growth in vegetative meristems.     

The influence of jasmonic acid on biophysical properties of potato leaf protoplasts and roots

Summary Jasmonic acid (JA) and its derivatives are a novel group of plant endogenous growth regulators. In our experiments some new data about the physiological effects of JA were obtained using electron paramagnetic resonance spectroscopy. Experiments were performed on potato plants (Solanum tuberosum L. cv. Vesna) grown in vitro. Different quantities of JA (0.1–10 M) were added to the growth medium. Root samples of plants grown on media supplemented with JA showed a more rapid spin probe N-oxyl-2,2,6,6-tetramethyl piperidine reduction than the control plants, which is a possible indicator of altered root permeability. Samples of leaf protoplasts were probed with methyl ester of 5-doxyl-haxadecanoic acid. We observed a membrane fluidity decrease in protoplasts isolated from plants grown on higher concentrations of JA (1 and 10 M).Abbreviations JA jasmonic acid - Me-JA methyl jasmonate - EPR electron paramagnetic resonance - RubisCO ribulose-1,5-biphosphate carboxylase/oxigenase - MeFASL(10,3) methyl ester of 5-doxyl-hexadecanoic acid - MES (2(N-morpholino)ethanesulfonic acid) - TEMPO N-oxyl-2,2,6,6-tetramethyl piperidine     

Regulation of SUP expression identifies multiple regulators involved in arabidopsis floral meristem development

During the course of flower development, floral homeotic genes are expressed in defined concentric regions of floral meristems called whorls. The SUPERMAN (SUP, also called FLO10) gene, which encodes a C2H2-type zinc finger protein, is involved in maintenance of the stamen/carpel whorl boundary (the boundary between whorl 3 and whorl 4) in Arabidopsis. Here, we show that the regulation of SUP expression in floral meristems is complex, consisting of two distinct phases, initiation and maintenance. The floral meristem identity gene LEAFY (LFY) plays a role in the initiation phase through at least two pathways, which differ from each other in the involvement of two homeotic genes, APETALA3 (AP3) and PISTILLATA (PI). AP3, PI, and another homeotic gene, AGAMOUS (AG), are further required for SUP expression in the later maintenance phase. Aside from these genes, there are other as yet unidentified genes that control both the temporal and spatial patterns of SUP expression in whorl 3 floral meristems. SUP appears to act transiently, probably functioning to trigger a genetic circuit that creates the correct position of the whorl 3/whorl 4 boundary.     

Regulation of jasmonic acid biosynthesis by silicon application during physical injury to Oryza sativa L.

We investigated the effects of silicon (Si) application on rice plants (Oryza sativa L.) and its responses in the regulation of jasmonic acid (JA) during wounding stress. Endogenous JA was significantly higher in wounded rice plants than in non-wounded. In contrast, Si treatment significantly reduced JA synthesis as compared to non-Si applications under wounding stress. mRNA expression of O. sativa genes showed down-regulation of lipoxygenase, allene oxide synthase 1, allene oxide synthase 2, 12-oxophytodienoate reductase 3, and allene oxide cyclase upon Si application and wounding stress as compared to non-Si-treated wounded rice plants. The physical injury-induced-oxidative stress was modulated by Si treatments, which resulted in higher catalase, peroxidase, and polyphenol oxidase activities as compared with non-Si-treated plants under wounding stress. The higher Si accumulation in rice plants also reduced the level of lipid peroxidation, which helped the rice plants to protect it from wounding stress. In conclusion, Si accumulation in rice plants mitigated the adverse effects of wounding through regulation of antioxidants and JA.