拟南芥紫色酸性磷酸酶基因(AtPAPs)对磷饥饿的响应

根据拟南芥基因组测序所获得的信息,对拟南芥2号染色 7个可能的紫色酸性磷酸酶基因进行了cDNA克隆、测序及生物信息学分析,并对其在磷饥饿状态下转录水平的表达模式进行了研究,发现大部分的AtPAPs都是组成性表达的,只有AtPAP9,AtPAP10是诱导表达的,其中AtPAP9的转录产物是磷饥饿重新诱导的,而AtPAP10是磷饥饿诱导增加的。     

High-Frequency Regeneration by Abscisic Acid (ABA) from Petiole Callus of Jatropha curcas

Jatropha curcas L. is attaining worldwide interest as an important biofuel crop. Experiments were conducted to improve the prevailing micropropagation technique as well as to develop a new ex vitro rooting method for J. curcas plant regeneration. Regeneration and ex vitro rooting efficiency was enhanced by augmenting the culture medium with abscisic acid (ABA). Different concentrations of 6-benzylaminopurine (BAP) and indole-3-butyric acid (IBA) were tested for callus generation from both in vitro and in vivo explants (leaf and petiole) on Murashige and Skoog (MS) medium. The best regenerative callus was achieved on MS medium supplemented with BAP (4.44 μM) and IBA (2.45 μM) from in vitro-cultured petioles. Highest regeneration (91%) was achieved by culturing petiole callus on MS medium supplemented with BAP (8.88 μM), IBA (0.49 μM), and ABA (1.9 μM), whereas 61% regeneration was obtained from in vitro leaf callus. Shoot proliferation and elongation was achieved on BAP (2.22 μM) and IAA (8.56 μM) with 10–13 shoots per explants. Highest rooting (65%) was achieved from M1 shoots (BAP, IAA, and ABA) on MS medium supplemented with IBA (2.45 μM), naphthaleneacetic acid NAA (0.54 μM), and 0.02% activated charcoal. Ex vitro rooting of 1-mo-old M1 shoots obtained from the charcoal-containing medium resulted optimum rooting (>72%) when transferred to polybags containing sterile sand. The plantlets were successfully acclimatized in soil with more than 98% survival rate in the greenhouse.     

Maternal Effects Govern Variable Dominance of Two Abscisic Acid Response Mutations in Arabidopsis thaliana

Three abscisic acid (ABA)-controlled responses (seed dormancy, inhibition of germination by applied ABA, and stomatal closure) were compared in wild-type versus homo- and heterozygotes of two Arabidopsis thaliana ABA-insensitive mutants, abi1 and abi2. We found that sensitivity of seeds to applied ABA is partially maternally controlled but that seed dormancy is determined by the embryonic genotype. The effects of the abi1 and abi2 mutations on ABA sensitivity of seed germination ranged from recessive to nearly fully dominant, depending on the parental source of the mutant allele. This maternal effect disappeared during vegetative growth. Stomatal regulation in heterozygotes showed substantial variability, but the average water loss was intermediate between that of homozygous mutants and wild type.     

三个拟南芥NAC同源基因突变体的ABA响应及下游基因表达分析

在获得拟南芥NAC同源基因(NAC019、NAC055和NAC072)双突变体和三突变体纯系的基础上,进一步分析它们对ABA响应的生理差异及其ABA诱导相关下游基因的表达变化,深入探讨它们与ABA响应的关系。结果表明,在种子绿胚建成的过程中,NAC055和NAC072基因与ABA响应相关;在根生长方面,三者在ABA响应中作用不明显。经ABA处理后,突变体nac072和nac055nac072与野生型比较,RAB18、RD29A和RD29B基因表达上调显著,推测在ABA响应的基因表达调控过程中,NAC072和NAC055起负调控协同作用,而NAC019则发挥拮抗作用。     

Control of the Co2 Responses of Stomata by Indol-3ylacetic Acid and Abscisic Acid

Previous studies of stomatal behaviour on detached epidermisof Commelina communis L. have suggested that abscisic acid (ABA)and C02 act independently to cause stomatal closure. Evidenceis presented here that if indol-3ylacetic acid (IAA) is addedto the medium used for incubating the epidermis, an interactionbetween ABA and Co₂ becomes apparent. Increasing concentrationsof IAA reduce the ability of the stomata to respond to CO₂,and ABA appears to antagonize this effect. Recognition of therole of IAA enables us to reconcile earlier conflicting reportsconcerning the interdependence of effects of ABA and Co₂on stomata.     

Abscisic Acid and Gibberellin-in Three Ungrafted Apple (Malus sylvestris) Rootstock Clones

ABA and gibberellin-like substances were extracted from roots, shoots, and leaves of most dwarfing M9, semi-dwarfing MM 106, and least dwarfing MM111 apple rootstock plants. Among tissues, the roots contained the largest and the shoots the smallest amounts of all the phytohormones studied. Plants of M9 contained the highest and MM111 the lowest ABA-like substances in all tissues tested. Gibberellin₄₊₇-like compounds were at the highest levels in the roots of MM111 and lowest in the roots of M9, whereas GA₃-like substance was in the reverse order. All three gibberellin-like compounds were highest in the shoots and leaves of MM111 and lowest in the respective tissues of M9 clone. Role of these phytohormones in the dwarfing mechanism is discussed.     

Structural Requirements of Abscisic Acid (ABA) and its Impact on Water Flow During Radial Transport of ABA Analogues Through Maize Roots

The effect of (+) (ABA) and (?)-abscisic acid and nine ABA metabolites, precursors or derivatives on radial water movement through maize roots, was investigated using a suction technique (Freundl and others 1998). (+)-ABA, (+)- and (?)-abscisyl aldehyde, (+)-8?-hydroxymethyl ABA, (+)-8?-methylene, and (+)-8?-acetylene ABA stimulated radial water transport. (?)-ABA, phaseic acid, and (+)-8?-acetylene methyl ABA were ineffective. ELISA analysis for ABA detected and apparent increase of free ABAxyl in xylem sap of excised root systems that were perfused with either (+)-abscisyl aldehyde, (+)-8?-methylene, (+)8?-acetylene-ABA, or ABA-glucose ester. The analogues (+)-8?-hydroxymethyl ABA and (?)-abscisyl aldehyde passed the cortex of maize roots without changing the ABAxyl. The data from this study permit conclusions about the structural requirements for hormonal regulation of hydraulic conductivity.     

高效液相色谱法同时测定银凤桃中的赤霉素和脱落酸

赤霉素(GA3)和脱落酸(ABA)是果实组织中的两个重要激素,本试验用SymmetryC18色谱柱(4.6mm×150mm),以乙腈和1.8%乙酸[V(CH3CN)∶V(1.8%CH3COOH)=1∶1]为流动相,流速为0.5mL·min-1,Wa-ters2487UV-检测器,在检测波长254nm,柱温25℃的条件下,同时分离并测定了银凤桃中的GA3和ABA。GA3和ABA的分离效果理想,回收率分别达到100.1%和99.8%,该方法测量灵敏度达10-2ng·g-1,精密度RSD%<0.1。     

The Effect of Abscisic Acid (ABA) on the Respiration and Uptake of Inorganic Phosphate by Potato Pith Discs

Abscisic acid (ABA) stimulates the oxygen uptake and inhibits the uptake of inorganic phosphate of discs of potato pith. It is assumed that ABA acts as an uncoupler of the oxydative phosphorylation in agreement with what was shown earlier for β inhibitor from resting potato peelings. The effect is probably not directly related to growth phenomena.     

8[prime]-Methylene Abscisic Acid (An Effective and Persistent Analog of Abscisic Acid)

We report here the synthesis and biological activity of a new persistent abscisic acid (ABA) analog, 8[prime]-methylene ABA. This ABA analog has one additional carbon atom attached through a double bond to the 8[prime]-carbon of the ABA molecule. (+)-8[prime]-Methylene ABA is more active than the natural hormone (+)-ABA in inhibiting germination of cress seed and excised wheat embryos, in reducing growth of suspension-cultured corn cells, and in reducing transpiration in wheat seedlings. The (+)-8[prime]-methylene analog is slightly weaker than (+)-ABA in increasing expression of ABA-inducible genes in transgenic tobacco, but is equally active in stimulating a transient elevation of the pH of the medium of corn cell cultures. In corn cells, both (+)-ABA and (+)-8[prime]-methylene ABA are oxidized at the 8[prime] position. ABA is oxidized to phaseic acid and (+)-8[prime]-methylene ABA is converted more slowly to two isomeric epoxides. The alteration in the ABA structure causes the analog to be metabolized more slowly than ABA, resulting in longer-lasting and more effective biological activity relative to ABA.     

Abscisic Acid Control of Lectin Accumulation in Wheat Seedlings and Callus Cultures : Effects of Exogenous ABA and Fluridone

Wheat germ agglutinin is found in wheat embryos and a similar lectin is present in the roots of older plants. We report here that 10 micromolar abscisic acid (ABA) produces an average two to three-fold enhancement in the amount of lectin in the shoot base and the terminal portion of the root system of hydroponically grown wheat seedlings. Although ABA stunts seedling growth, a similar growth inhibition produced by ancymidol is not accompanied by elevated lectin levels. To further clarify the role of ABA, wheat callus cultures were employed. Callus derived from immature embryos was grown on growth medium containing various combinations of ABA and 2,4-dichlorophenoxyacetic acid. Those grown in the presence of 10 micromolar ABA exhibit the largest increases in lectin compared to material grown on other regimes. The involvement of ABA in lectin accumulation was further probed with fluridone, an inhibitor of carotenoid synthesis which has also been linked to depressed levels of endogenous ABA. Wheat seedlings grown in the presence of 1 or 10 milligrams per liter fluridone have few or no carotenoids, and wheat germ agglutinin levels in the shoot base and roots are lower compared to controls. The greatest effect (a 39% reduction in the shoot base) is produced at an herbicide concentration of 10 milligrams per liter. Exogenous 10 micromolar ABA greatly stimulates lectin accumulation in the presence of fluridone, but the levels are not as high as those produced by ABA alone. These results indicate that lectin synthesis is under ABA control in both wheat embryos and adult plants.     

Abscisic acid (ABA) inhibition of lateral root formation involves endogenous ABA biosynthesis in Arachis hypogaea L.

ABA has been found to play a significant role in post-embryonic developmental in peanut seedlings. The results from the current study indicate that in the presence of exogenous 10 μmol l⁻¹ ABA, lateral roots (LRs) number decreased and seedling development was delayed. This effect was eliminated by 25 μmol l⁻¹ naproxen, an inhibitor of ABA biosynthesis. The Arabidopsis mutant deficient in ABA biosynthesis, nced3, displays a phenotype with more and longer LRs. We found that ABA decreased root-branching in peanut in a dose-dependent way. ABA-treated seedlings showed higher endogenous ABA levels than the control and naproxen-treated seedlings. RT-PCR results indicated that the expression of AhNCED1, a key gene in the ABA biosynthetic pathway, was significantly up-regulated by exogenous ABA in peanut. The mRNA levels of AhNCED1 began to increase 2 days after ABA treatment. The results from the current study show that ABA inhibits peanut LR development by increasing endogenous ABA contents.     

A Set of Three Genes Regulates Photoperiodic Responses of Flowering in Rice (Oryza sativa)

Differentiation in photoperiodic response of flowering has been key to the evolution and wide geographic distribution of rice, an essentially short-day plant. Crosses were made such that the hybrid F1 plants flower later than the late-flowering parents to investigate the genetic basis underlying this differentiation. From initial experiments, three major genes for flowering time were identified from four naturally occurring variants under natural long-day conditions. An F2-derived trigenic mutant line bred-true for a day-neutral response was selected and used as the recipient to synchronize the genetic background for the major genes. Experiments conducted under various daylengths indicated that these genes are responsible for photoperiodic sensitivity and the trihybrid has a critical daylength between 13.5 and 14 h. The three genes regulate photoperiodic responses qualitatively and quantitatively through complementary and other epistatic effects, respectively. The complementation suggests that the three genes act in a linear manner to repress the transition from the vegetative to reproductive phases under long daylengths. This set of genes also provides a model to understand the genetic mechanism underlying the elongated vegetative growth period in the F1 generation, which is usually an obstacle to the use of heterosis, and the selection for early maturation in rice breeding.     

Exogenous Catalase and Ascorbate Modify the Effects of Abscisic Acid (ABA) on Root Hydraulic Properties in Phaseolus vulgaris L. Plants

Abscisic acid (ABA) modifies the hydraulic properties of roots by increasing root water flux (J_v). The role of reactive oxygen species (ROS) in this ABA-induced process was evaluated. At the same time, some antioxidant enzyme activities in root tissues were measured. Phaseolus vulgaris plants were grown hydroponically, and different concentrations of ABA in combination with catalase enzyme or ascorbate were added to the nutrient solution. Catalase treatment had no effect by itself (no ABA) and had little or only a small stimulatory effect at ABA concentrations of 1, 50, and 100 μM, but it partially inhibited the ABA effect at 5 μM. Ascorbate by itself doubled J_v and root hydraulic conductance over the control value. In the presence of ABA, ascorbate partially or, at 100 μM, completely inhibited that ABA stimulation of J_v. These results are discussed in relationship to the possibility that ABA signaling in the roots involves ROS.     

Stomatal Responses of Pearl Millet (Pennisetum americanum (L.) Leeke) Genotypes, in Relation to Abscisic Acid and Water Stress

Stomatal responses to water stress and to applied (±)-abscisicacid (ABA) were examined in genotypes of pearl millet (Pennisetumamericanum (L.) Leeke) known to differ in amounts of endogenousABA accumulating during drought. In both a pot and a field experiment,Serere 39, a genotype with a high capacity to accumulate ABA,showed a higher stomatal sensitivity to water stress than didthe ‘low’ ABA accumulator, BJ 104. In the fieldexperiment, a third genotype, B282, accumulating least amountsof ABA, also had the lowest stomatal sensitivity to water stress. There were no significant differences between these genotypesin stomatal response to applied (±)-ABA, or in the relationshipsbetween leaf conductance and levels of endogenous ABA. It isconcluded that the differences in accumulation of endogenousABA by these genotypes of pearl millet are of functional significance,and that endogenous ABA generated during a water stress whichdevelops over days or weeks mediates stomatal responses to suchstress.     

Abscisic Acid Structure-Activity Relationships in Barley Aleurone Layers and Protoplasts (Biological Activity of Optically Active,Oxygenated Abscisic Acid Analogs)

Optically active forms of abscisic acid (ABA) and their oxygenated metabolites were tested for their biological activity by examining the effects of the compounds on the reversal of gibberellic acid-induced [alpha]-amylase activity in barley (Hordeum vulgare cv Himalaya) aleurone layers and the induction of gene expression in barley aleurone protoplasts transformed with a chimeric construct containing the promoter region of an albumin storage protein gene. Promotion of the albumin storage protein gene response had a more strict stereochemical requirement for elicitation of an ABA response than inhibition of [alpha]-amylase gene expression. The naturally occurring stereoisomer of ABA and its metabolites were more effective at eliciting an ABA-like response. ABA showed the highest activity, followed by 7[prime]-hydroxyABA, with phaseic acid being the least active. Racemic 8[prime]-hydroxy-2[prime],3[prime]-dihydroABA, an analog of 8[prime]-hydroxyABA, was inactive, whereas racemic 2[prime],3[prime]-dihydroABA was as effective as ABA. The differences in response of the same tissue to the ABA enantiomers lead us to conclude that there exists more than one type of ABA receptor and/or multiple signal transduction pathways in barley aleurone tissue.