Higher Abscisic Acid Content Research Articles

Survival strategies of citrus rootstocks subjected to drought.

Two citrus rootstocks, Rangpur lime (RL) and Sunki Maravilha mandarin (SM), were analyzed either ungrafted or grafted with their reciprocal graft combinations or with shoot scions of two commercial citrus varieties: Valencia orange (VO) and Tahiti acid lime (TAL). All graft combinations were subjected to distinct watering regimes: well-watered, severe drought and rehydration. Growth and water relation parameters, gas exchange as well as sugar and hormone profiles were determined. Data indicated that RL adopted a dehydration avoidance strategy and maintained growth, whereas SM adopted a dehydration tolerance strategy focused on plant survival. Compared with RL, the leaves and roots of SM exhibited higher concentrations of abscisic acid and salicylic acid, which induced drought tolerance, and accumulation of carbohydrates such as trehalose and raffinose, which are important reactive oxygen species scavengers. SM rootstocks were able to transfer their survival strategy to the grafted shoot scions (RL, VO, TAL). Because of their contrasting survival strategies, RL reached the permanent wilting point more quickly than SM whereas SM recovered from prolonged droughts more efficiently than RL. This is one of the most complete studies of drought tolerance mechanisms in citrus crops and is the first to use reciprocal grafting to clarify scion/rootstock interactions.

Melatonin enhances cold tolerance in drought-primed wild-type and abscisic acid-deficient mutant barley.

Melatonin is involved in multiple plant developmental processes and various stress responses. To explore the roles of melatonin played as well as its association with abscisic acid (ABA) in a process of drought priming-induced cold tolerance (DPICT), a wild-type barley and its ABA-deficient mutant Az34 counterpart were selected for comparison, in which the effects of melatonin application (either foliarly or rhizospherically) and/or drought priming on the cold tolerance of both types of barleys were systematically investigated. It was demonstrated that the early drought priming induced an increase of endogenous melatonin production, which is not ABA dependent. In addition, exogenously applied melatonin resulted in higher ABA concentration in the drought-primed plants than in the nonprimed plants when exposed to cold stress, indicating that ABA responded in a drought-dependent manner. The interplay of melatonin and ABA leads to plants maintaining better water status. Drought priming-induced melatonin accumulation enhanced the antioxidant capacity in both chloroplasts and mitochondria, which sustained the photosynthetic electron transport in photosynthetic apparatus of the plants under cold stress. These results suggest that the exogenous melatonin application enhances the DPICT by modulating subcellular antioxidant systems and ABA levels in barley.

Loss of heterophylly in aquatic plants: not ABA-mediated stress but exogenous ABA treatment induces stomatal leaves in Potamogeton perfoliatus.

Heterophyllous aquatic plants produce aerial (i.e., floating and terrestrial) and submerged leaves—the latter lack stomata—while homophyllous plants contain only submerged leaves, and cannot survive on land. To identify whether differences in morphogenetic potential and/or physiological stress responses are responsible for variation in phenotypic plasticity between two plants types, responses to abscisic acid (ABA) and salinity stress were compared between the closely related, but ecologically diverse pondweeds, Potamogeton wrightii (heterophyllous) and P. perfoliatus (homophyllous). The ABA-treated (1 or 10 μM) P. wrightii plants exhibited heterophylly and produced leaves with stomata. The obligate submerged P. perfoliatus plants were able to produce stomata on their leaves, but there were no changes to leaf shape, and stomatal production occurred only at a high ABA concentration (10 μM). Under salinity stress conditions, only P. wrightii leaves formed stomata. Additionally, the expression of stress-responsive NCED genes, which encode a key enzyme in ABA biosynthesis, was consistently up-regulated in P. wrightii, but only temporarily in P. perfoliatus. The observed species-specific gene expression patterns may be responsible for the induction or suppression of stomatal production during exposure to salinity stress. These results suggest that the two Potamogeton species have an innate morphogenetic ability to form stomata, but the actual production of stomata depends on ABA-mediated stress responses specific to each species and habitat.Electronic supplementary materialThe online version of this article (doi:10.1007/s10265-016-0844-x) contains supplementary material, which is available to authorized users.

Long-term effects of abscisic acid (ABA) on the grape berry phenylpropanoid pathway: Gene expression and metabolite content

ABA has been proposed as the main signal triggering the onset of the ripening process in grapes, and modulating the secondary metabolism in grape berry skins. To determine the effect of ABA on secondary metabolism in berries, clusters of Carménère were sprayed with 0 μLL−1 ABA; 50 μLL−1 ABA and 100 μLL−1 ABA during pre-véraison, and the gene expression of the transcription factors and enzymes of the phenylpropanoid pathway were assessed from véraison to 70 days after véraison (DAV). Additionally, flavonols, tannins and anthocyanins were assessed from véraison until harvest (110 DAV). ABA accelerated sugar and anthocyanin accumulation at véraison. The grape transcript abundance of VvDFR, VvANS, VvUFGT and VvMybA1, all peaking around véraison mimicked the concentration of ABA throughout the season. The highest anthocyanin concentration occurred 35 DAV for all treatments, but higher pigment concentrations were observed in ABA-treated berries at véraison and from 60 to 70 DAV to harvest. VvPAL was also increased by treatment at the higher concentration of ABA from véraison to 40 DAV. Regarding flavanol synthesis, VvLAR2 and VvMyb4A decreased from véraison until 40 DAV and then increased again until 70 DAV. Compared to the control, both ABA treatments resulted in a less-than-proportional reduction of the expression of both genes compared to the control and, after 40 DAV, in a more-than-proportional increase compared to the control, suggesting a long-term effect of the pre-véraison ABA spray on the berries. A concomitant increase in flavanols was observed in berries after 40 DAV, and this occurred at a higher extent in berries treated with the highest ABA concentration.

Expression analysis of ABA- and GA-related genes during four stages of bud dormancy in Japanese apricot (Prunus mume Sieb. et Zucc)

ABSTRACTSeasonal dormancy in deciduous fruit trees is a complex physiological state, which is regulated by many plant hormones and genes. Abscisic acid (ABA) and gibberellic acid (GA3) are known to be particularly important in controlling dormancy. We measured the concentrations of these two hormones in flower buds (collected during para-, endo-, and eco-dormancy, and at the dormancy-release stage) and vegetative buds (collected monthly from 20 November 2012 to 20 February 2013) of two cultivars of Japanese apricot (Prunus mume Sieb. et Zucc), ‘Bungo’ and ‘Taoxingmei’, using liquid chromatography and tandem mass spectrometry (LC–MS/MS). Levels of expression of two zinc-finger family genes CCCH and C2H2 and the GA20ox (gibberellin 20 oxidase) gene (GenBank Accession No. Pm013607), as candidates for dormancy-controlling genes, were analysed at each sampling time using real-time RT-quantitative PCR (RT-qPCR). Expression analyses indicated that both zinc-finger family genes exhibited high transcript levels in flower buds of both cultivars during para-dormancy, concomitant with high ABA concentrations. The zinc-finger family genes were relatively highly expressed in vegetative buds of both cultivars on 20 November 2012 (autumn). In addition, high concentration of GA3 in flower buds at the dormancy-release stage suggested that GA3 plays an important role in controlling the release of bud dormancy. High levels of expression of the GA20ox gene during eco-dormancy and at the dormancy-release stage might have a prominent effect on dormancy-release by regulating gibberellin (GA) signalling in Japanese apricot. These results will contribute to increasing our understanding of ABA- and GA-mediated seasonal dormancy mechanisms in Japanese apricot.

Determination of Abscisic Acid and its Relationship to Drought Stress Based on Cowpea Varieties with Different Capability of Drought Resistance

Cowpea (Vigna unguiculata L.) is one of the most important grain legume supplying necessarily dietary proteins. Although its can tolerate drought environment, still the severe condition can limit the growth and development of this plant. Abscisic acid (ABA) has a crucial function in stress physiology, but little information is available for methods describing ABA determination in cowpea and its relationship to drought stress based on cowpea varieties with different capability of drought resistance. Here, an effectual approach based on high-performance liquid chromatography (HPLC) method was established to separate and determine the endogenous abscisic acid in cowpea and further the cowpea varieties with different capability of drought resistance were used to explore relationships between ABA content and drought stress. The results potentially provided useful reference for the cultivation of cowpea crop. Results-This method showed good liner regression (R2 = 0.9998), coupled with high stability, precision and repeatability. The endogenous ABA decreased under drought treatment and the drought sensitive line had higher ABA content than drought resistant one, suggesting ABA performs a vital function in cowpea’s response and resistance to drought stress. The studies potentially provided useful reference for the cultivation and breeding of cowpea crop.

Differential Responses of Antioxidants, Abscisic Acid, and Auxin to Deficit Irrigation in Two Perennial Ryegrass Cultivars Contrasting in Drought Tolerance

Water deficit is a major limiting factor for grass culture in many regions with physiological mechanisms of tolerance not yet well understood. Antioxidant isozymes and hormones may play important roles in plant tolerance to water deficit. This study was designed to investigate antioxidant enzymes, isozymes, abscisic acid (ABA), and indole-3-acetic acid (IAA) responses to deficit irrigation in two perennial ryegrass (Lolium perenne L.) cultivars contrasting in drought tolerance. The plants were subjected to well-watered {100% container capacity, 34.4% ± 0.21% volumetric moisture content (VWC), or deficit irrigation [30% evapotranspiration (ET) replacement; 28.6% ± 0.15% to 7.5% ± 0.12% VWC]} conditions for up to 8 days and rewatering for 4 days for recovery in growth chambers. Deficit irrigation increased leaf malondialdehyde (MDA) content in both cultivars, but drought-tolerant Manhattan-5 exhibited lower levels relative to drought-sensitive Silver Dollar. Superoxide dismutase (SOD) activity declined and then increased during water-deficit treatment. ‘Manhattan-5’ had higher SOD activity and greater abundance of SOD1 isozyme than ‘Silver Dollar’ under water deficit. Deficit irrigation increased catalase (CAT) and ascorbate peroxidase (APX) activity in ‘Manhattan-5’, but not in ‘Silver Dollar’. ‘Manhattan-5’ had higher CAT, APX, and peroxidase (POD) activity than ‘Silver Dollar’ during water limitation. Deficit irrigation increased mRNA accumulation of cytosolic cupper/zinc SOD (Cyt Cu/Zn SOD), whereas gene expression of manganese SOD (Mn SOD) and peroxisome APX (pAPX) were not significantly altered in response to deficit irrigation. No differences in Cyt Cu/Zn SOD, Mn SOD, and pAPX gene expression were found between the two cultivars under deficit irrigation. Water limitation increased leaf ABA and IAA contents in both cultivars, with Silver Dollar having a higher ABA content than Manhattan-5. Change in ABA level may regulate stomatal opening and oxidative stress, which may trigger antioxidant defense responses. These results indicate that accumulation of antioxidant enzymes and ABA are associated with perennial ryegrass drought tolerance. Activity and isozyme assays of key antioxidant enzymes under soil moisture limitation can be a practical screening approach to improve perennial ryegrass drought tolerance and quality.

Impact of temperature and sunlight on the skin coloration of the ‘Kyoho’ table grape

We evaluated the impact of increased temperature and sunlight exposure, features of global warming, on the skin coloration of ‘Kyoho’ table grape berries. Skin coloration, anthocyanin accumulation, abscisic acid (ABA) content, and transcript levels of anthocyanin biosynthetic genes in the skins were examined during the ripening season under continuous 24°C, 27°C and 30°C temperatures together with a sun or shade treatment. Skin coloration and anthocyanin accumulation were sufficient in the berries of plants ripened at 24°C with a sun-exposure treatment. They also had higher ABA contents and anthocyanin biosynthetic gene transcript levels than grapes under higher temperatures. The skins of grapes ripened at 27°C or 30°C showed insufficient coloration and low levels of anthocyanin accumulation, ABA content, and anthocyanin biosynthetic gene transcripts levels, irrespective of the light conditions. These results suggest that temperatures exceeding 27°C during the ripening season lead to insufficient berry coloration as a result of low levels of ABA and anthocyanin biosynthetic gene expression levels.

Effects of abscisic acid on chemical components content and color of Glycyrrhiza uralensis

An experiment was conducted using cultivated Glycyrrhiza uralensis in age of one year to study the effects of abscisic acid (ABA) on chemical components content and color of G. uralensis. By using different concentrations of ABA spraying on leaves, the change of the chemical component content was analyzed within 45 d after ABA stimulation, and the effects on quality were studied combined with colorimetric analysis data. It turned out that in some sense the content of glycyrrhizic acid and liquiritin had increased within 45 d, especially for liquiritin. After high concentrations of ABA (3.96 mg · L(-1)) stimulating, the content of glycyrrhizic acid rose 52% while liquiritin up 392% within 30 d. Then they both showed a decline in the content of glycyrrhizic acid and liquiritin on 45 d. Color index values of a* and b* were all significantly higher than that of the control group within 45 d, which meant the color of powders turned toward red and yellow. The conclusion was that ABA (3.96 mg · L(-1)) stimulating could not only improve the quality in the traditional sense through the color of G. uralensis, but also in the modern sense by improving the content of glycyrrhizic acid and liquiritin.

Mechanisms for the influence of citrus rootstocks on fruit size.

To obtain insight into potential mechanisms underlying the influence of rootstock on fruit size, we performed a comparative analysis of 'Shatangju' mandarin grafted onto two rootstocks. The results demonstrated that trees grafted onto Canton lemon produced larger fruits through an enhancement of cell expansion in the ripening period. The difference in fruit size may be due to greater auxin levels in fruits from trees on Canton lemon, and different auxin levels may be produced by parent trees as the result of AUX1 upregulation. Rootstocks also modulate auxin signaling by affecting the transcription of several auxin response factor genes. There were higher abscisic acid concentrations in fruits of 'Shatangju'/Trifoliate orange, resulting in an inhibition of fruit growth and cell expansion through suppression of the synthesis of growth promoting hormones. Furthermore, expansins may be involved in the regulation of final fruit size by influencing cell expansion. Multiple pathways likely exist in citrus rootstocks that regulate fruit size.

Pulsing Treatments of Abscisic Acid and Sucrose for Improving Postharvest Quality of Cut Lily Flowers

Abscisic acid (ABA), as a senescence phytohormone, has been proved to be related to flower petal senescence in rose (Mayak and Halevy, 1972; Kumar et al., 2008) and carnation (Nowak and Veen, 1982). Higher ABA concentrations were found in short–lived cultivars compared to long–lived rose cultivars (Halevy and Mayak, 1975). Exogenous application of ABA leads to enhancement of aging–related process in daffodil petals (Hunter et al., 2004). ABA, as one of the preservation agents, was also applied in the fresh–keeping of cut roses (Kohl and Rundle, 1972), Baccara roses (Pompodakis and Joyce, 2003; Pompodakis et al., 2004) and Eustoma flowers (Shimizu–Yumoto and Ichimura, 2009). ABA prolongs the vase life of cut roses with leaves, but shortens the vase life of leafless cut roses (Halevy et al., 1974). ABA can regulate water balance of cut flower through controlling stomata opening, increase the postharvest quality, and extend the vase life of cut flowers (Kohl and Rundle, 1972; Pompodakis and Joyce, 2003; Pompodakis et al., 2004). On the other hand it has been reported that ABA regulates water balance through ways other than stomata opening regulation (Borohov et al., 1976), the application of ABA did not affect the transpiration (Ichimura and Shimizu–Yumoto, 2007). ABA treatment can alleviate the sucrose–induced leaf chlorosis and improve the quality of cut flowers (Pompodakis and Joyce, 2003; Shimizu–Yumoto and Ichimura, 2009). Lilies are the world famous cut flowers with high ornamental value. Yang et al. (1996) indicated that ABA probably is the main factor affecting senescence of cut lilies, because morphology of cut flowers showed senescence symptoms following the peak of ABA, while ethylene can accelerate the aging process only to a certain extent. But Li et al. (2012) indicated that the addition of lower concentrations of ABA with sucrose and 8–hydroxyquinoline citrate (8–HQC) induced the increase of fresh weight, and partly alleviate the sucrose–induced leaf yellowing. Based on the above researches, the preservation mechanism of ABA in cut lilies is still not clear. Lilium ‘Sorbonne’ (Oriental hybrid group) was used as an experimental material in this study to observe the preservation effect of ABA, and to confirm further the preservation mechanism of ABA by determining the physiological indices and ethylene release of cut ‘Sorbonnes’ petals during postharvest.

金银花容器苗对干旱胁迫下接种根际促生细菌的生理响应

PDF HTML阅读 XML下载 导出引用 引用提醒 金银花容器苗对干旱胁迫下接种根际促生细菌的生理响应 DOI: 10.5846/stxb201402180282 作者: 作者单位: 山东省林业科学研究院 作者简介: 通讯作者: 中图分类号: Q945; S718.83 基金项目: 山东省科技发展计划专项资助(2010GSF10621, 2014GNC113006) Physiological responses of Lonicera japonica container seedlings to plant growth- promoting rhizobacteria inoculation under drought stress Author: Affiliation: Shandong Academy of Forest,Shandong Engineering Research Center for Ecological Restoration of Forest Vegetation Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在盆栽试验条件下,以金银花容器苗为试材,研究了不同干旱强度下接种蜡样芽孢杆菌(Bacillus cereus)L90对植物生理特征的影响。结果表明:随着干旱胁迫强度的增加,金银花容器苗的光合速率和气孔导度逐渐降低;而干旱环境下接种L90可显著提高气孔导度,缓解干旱胁迫对净光合速率的抑制;且干旱强度增加,缓解效果增强。接种B. cereus L90可显著抑制干旱胁迫下金银花容器苗PSⅡ最大光化学效率、实际光化学效率和光化学猝灭系数的降低,抑制非光化学猝灭系数的升高。虽然L90并没有提高对照处理中光合色素的绝对含量,但可显著抑制干旱环境下金银花叶片中光合色素的分解。干旱显著降低了金银花叶片中细胞分裂素含量,增加了脱落酸(ABA)的含量;在干旱胁迫下,接种L90可显著提高叶片中细胞分裂素的含量,并可促使根部产生的ABA运输到叶片中。干旱胁迫程度较轻时,L90对金银花容器苗的相对含水量和相对电导率影响不显著;而在重度干旱时,同对照相比,干旱及接种L90处理的相对含水量分别降低20.56%和10.21%,相对电导率分别提高31.42%和16.08%,接种L90处理的变化幅度明显较小。因此,干旱生境下接种B. cereus L90,可增加叶片中细胞分裂素含量,抑制光合色素的分解及光合能力的下降,提高金银花容器苗在干旱环境中的适应能力。 Abstract:Plant growth-promoting rhizobacteria (PGPR) are rhizosphere inhabitants that promote plant growth and suppress diseases. One of the proposed mechanisms through which PGPR enhance plant growth is the production of plant growth regulators, especially cytokinin. However, little information is available about the effects of cytokinin-producing PGPR inoculation on the drought stress response. Soil water availability is a crucial determining factor of plant yield, because drought stress inhibits stem elongation, leaf expansion, and stomatal movement. Therefore, a strain of rhizobacteria with a high rate of cytokinin production, Bacillus cereus L90, was selected for use in this investigation. The bacteria were obtained from the rhizosphere of a walnut tree, where water is limited and frequent dry periods occur. Serial dilution and a bioassay for the detection of cytokinin production were both used to isolate and screen the bacterial strain from the soil sample. This study investigated how PGPR affects the physiological characteristics of Lonicera japonica Thunb. under different drought stress treatments (light, moderate, severe, and a control). The combined effects of B. cereus L90 inoculation and various levels of drought stress on the photosynthetic characteristics, chlorophyll fluorescence parameters, photosynthetic pigment, cytokinin and ABA(abscisic acid) concentrations, relative water content, and relative electrolyte leakage were studied using the pot method. The results showed that the net photosynthetic rate and stomatal conductance decreased with increasing drought stress. However, B. cereus L90 inoculation was associated with an increase in stomatal conductance and net photosynthetic rate in plants under drought stress. B. cereus L90 inoculation reduced the negative impact of drought stress on the maximum photochemical efficiency of PSⅡ, the actual photochemical efficiency of PSⅡ, and the photochemical quenching coefficient. B. cereus L90 inoculation also prevented the non-photochemical quenching coefficient from increasing. Although no significant difference was observed under well-watered conditions, the leaves of inoculated drought-stressed L. japonica seedlings had higher photosynthetic pigments contents compared to those of non-inoculated seedlings. The roots of inoculated L. japonica seedlings had higher ABA content compared to non-inoculated seedlings. The elevated levels of cytokinins in L. japonica leaves and the higher concentration of ABA are both associated with drought stress. B. cereus L90 inoculation significantly increased the cytokinin content of drought-stressed L. japonica leaves, and improved the rate of transportation of ABA from the roots to the leaves. No significant differences in relative water content and relative electrical conductance were observed between inoculated and non-inoculated seedlings under light drought stress. Compared to the irrigated control, under severe drought stress, the relative water content of non-inoculated seedlings decreased by 20.56%, while that of inoculated seedlings decreased by 10.21%. However, the relative electrical conductance of inoculated and non-inoculated seedlings under severe drought stress increased by 31.42% and 16.08%, respectively. These results demonstrate that inoculation of B. cereus L90 under drought stress increases the cytokinin content of L. japonica leaves, and interferes with the suppression of photosynthetic pigments and net photosynthetic rate. Thus, B. cereus L90 inoculation could improve the adaptability ability of L. japonica seedlings to drought conditions. In conclusion, inoculation of cytokinin-producing PGPR could be used to alleviate drought stress and interfere with the suppression of physiological processes, showing real potential for practical use in arid environments as a drought stress inhibitor. 参考文献 相似文献 引证文献

外源激素ABA影响新疆荒漠盐生植物异子蓬异型种子萌发机制初探

PDF HTML阅读 XML下载 导出引用 引用提醒 外源激素ABA影响新疆荒漠盐生植物异子蓬异型种子萌发机制 DOI: 10.5846/stxb201405130978 作者: 作者单位: 新疆大学生命科学与技术学院/新疆生物资源基因工程重点实验室,新疆大学生命科学与技术学院/新疆生物资源基因工程重点实验室,新疆大学生命科学与技术学院/新疆生物资源基因工程重点实验室,新疆大学生命科学与技术学院/新疆生物资源基因工程重点实验室,新疆大学生命科学与技术学院/新疆生物资源基因工程重点实验室,新疆大学生命科学与技术学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31260037,31060027);新疆自治区优秀青年科技人才培养项目(2013721013);新疆生物资源基因工程重点实验室开放基金(XJDX0201-2011-03) Effects of exogenous abscisic acid on heteromorphic seed germination of Suaeda aralocaspica, a typical halophyte of Xinjiang desert region Author: Affiliation: Xinjiang Key Laboratory of Biological Resources and Genetic Engineering,College of Life Science and Technology,Xinjiang University,Xinjiang Key Laboratory of Biological Resources and Genetic Engineering,College of Life Science and Technology,Xinjiang University,Xinjiang Key Laboratory of Biological Resources and Genetic Engineering,College of Life Science and Technology,Xinjiang University,Xinjiang Key Laboratory of Biological Resources and Genetic Engineering,College of Life Science and Technology,Xinjiang University,Xinjiang Key Laboratory of Biological Resources and Genetic Engineering,College of Life Science and Technology,Xinjiang University,Xinjiang Key Laboratory of Biological Resources and Genetic Engineering,College of Life Science and Technology,Xinjiang University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以新疆荒漠盐生植物异子蓬(Suaeda aralocaspica)异型种子为材料,通过外源ABA直播(长时间)与浸种(短时间)处理分别研究不同浓度(0、0.5、1.0、5.0、10.0 μmol/L)ABA对异型种子萌发、幼苗生长的影响,并通过定量PCR技术分析与萌发相关的ABC转运蛋白基因、丝裂原活化蛋白激酶激酶基因和DNA修复和转录因子基因在5.0 μmol/L ABA处理下的表达规律,探讨外源ABA影响异子蓬异型种子萌发差异的机制。结果显示:(1)外源ABA直播处理下,褐色种子萌发及幼苗生长均受到明显抑制,黑色种子的萌发和幼苗生长在低浓度被促进,较高浓度被显著抑制;短时间浸种处理,能够同时促进异型种子的萌发及幼苗生长,且随ABA浓度增加促进效应增强。(2)直播萌发后,褐色种子中3个基因的表达量与对照相比均不变或降低表达(除了DNA修复和转录因子基因在8 h显著升高),黑色种子与对照相比均上调表达(除了ABC转运蛋白基因在8h显著下调);短时间浸种萌发后,褐色种子中3个基因的表达量均比对照显著升高,黑色种子中升高不明显。基因表达规律与种子萌发结果趋势一致,暗示ABA浸种可能触发了异子蓬种子萌发内在机制并对随后的萌发过程产生促进作用。而黑色种子对ABA处理表现出较好的萌发响应,可能是其幼苗能抵御荒漠地区逆境环境的重要原因。 Abstract:In order to examine the effects of exogenous abscisic acid (ABA) on germination and seedling growth of heteromorphic Suaeda aralocaspica seeds, we either directly sowed (long-term treatment) or presoaked (short-term treatment) the two seed morphs under different concentrations (0, 0.5, 1.0, 5.0, 10.0 μmol/L) of ABA. To further understand the molecular mechanism of exogenous ABA effects on different germination characteristics of heteromorphic seeds of S. aralocaspica, we examined the expression of three genes with known functions in seed germination:ABC transporter family protein, mitogen-activated protein kinase kinase, and DNA repair and transcription factor. Gene expression was analyzed using quantitative PCR on directly sown and presoaked seeds treated with 5.0 μmol/L ABA. The results revealed two findings:(1) For directly sown seeds, different concentrations of exogenous ABA inhibited germination and seedling growth of brown seeds significantly, while these processes in black seeds were accelerated by lower concentrations of ABA, rather than by higher concentrations. In contrast, pre-soaking promoted germination and seedling growth of both types of seed, and this effect increased at higher concentrations of ABA. (2) Quantitative PCR revealed that, for directly sown brown seeds, only the expression level of the gene for DNA repair and transcription factor increased significantly at 8 h compared to that of control seeds. In black seeds, the genes for DNA repair and transcription factor and for mitogen-activated protein kinase kinase were significantly up regulated compared to those in the control. For pre-soaked seeds, treatment with ABA markedly increased the expression levels of all three genes in brown seeds rather than in black seeds. Expression patterns of the three genes were consistent with the results of seed germination. These results suggest that presoaking with ABA may trigger the internal germination mechanism of S. aralocaspica seeds and accelerate the subsequent germination process. The stronger response of black seeds to ABA treatment may be an important adaptation to the harsh and unpredictable environment of Xinjiang desert region. 参考文献 相似文献 引证文献

Overexpression of EsMcsu1 from the halophytic plant Eutrema salsugineum promotes abscisic acid biosynthesis and increases drought resistance in alfalfa (Medicago sativa L.).

The stress phytohormone abscisic acid (ABA) plays pivotal roles in plants' adaptive responses to adverse environments. Molybdenum cofactor sulfurases influence aldehyde oxidase activity and ABA biosynthesis. In this study, we isolated a novel EsMcsu1 gene encoding a molybdenum cofactor sulfurase from Eutrema salsugineum. EsMcus1 transcriptional patterns varied between organs, and its expression was significantly upregulated by abiotic stress or ABA treatment. Alfalfa plants that overexpressed EsMcsu1 had a higher ABA content than wild-type (WT) plants under drought stress conditions. Furthermore, levels of reactive oxygen species (ROS), ion leakage, and malondialdehyde were lower in the transgenic plants than in the WT plants after drought treatment, suggesting that the transgenic plants experienced less ROS-mediated damage. However, the expression of several stress-responsive genes, antioxidant enzyme activity, and osmolyte (proline and total soluble sugar) levels in the transgenic plants were higher than those in the WT plants after drought treatment. Therefore, EsMcsu1 overexpression improved drought tolerance in alfalfa plants by activating a series of ABA-mediated stress responses.

Abscisic Acid Promotion of Arbuscular Mycorrhizal Colonization Requires a Component of the PROTEIN PHOSPHATASE 2A Complex

Legumes can establish intracellular interactions with symbiotic microbes to enhance their fitness, including the interaction with arbuscular mycorrhizal (AM) fungi. AM fungi colonize root epidermal cells to gain access to the root cortex, and this requires the recognition by the host plant of fungus-made mycorrhizal factors. Genetic dissection has revealed the symbiosis signaling pathway that allows the recognition of AM fungi, but the downstream processes that are required to promote fungal infection are poorly understood. Abscisic acid (ABA) has been shown to promote arbuscule formation in tomato (Solanum lycopersicum). Here, we show that ABA modulates the establishment of the AM symbiosis in Medicago truncatula by promoting fungal colonization at low concentrations and impairing it at high concentrations. We show that the positive regulation of AM colonization via ABA requires a PROTEIN PHOSPHATASE 2A (PP2A) holoenzyme subunit, PP2AB'1. Mutations in PP2AB'1 cause reduced levels of AM colonization that cannot be rescued with permissive ABA application. The action of PP2AB'1 in response to ABA is unlinked to the generation of calcium oscillations, as the pp2aB'1 mutant displays a normal calcium response. This contrasts with the application of high concentrations of ABA that impairs mycorrhizal factor-induced calcium oscillations, suggesting different modes of action of ABA on the AM symbiosis. Our work reveals that ABA functions at multiple levels to regulate the AM symbiosis and that a PP2A phosphatase is required for the ABA promotion of AM colonization.

Drought priming at vegetative growth stages improves tolerance to drought and heat stresses occurring during grain filling in spring wheat

Plants of spring wheat (Triticum aestivum L. cv. Vinjett) were exposed to moderate water deficit at the vegetative growth stages six-leaf and/or stem elongation to investigate drought priming effects on tolerance to drought and heat stress events occurring during the grain filling stage. Compared with the non-primed plants, drought priming could alleviate photo-inhibition in flag leaves caused by drought and heat stress episodes during grain filling. In the primed plants, drought stress inhibited photosynthesis mainly through decrease of maximum photosynthetic electron transport rate, while decrease of the carboxylation efficiency limited photosynthesis under heat stress. The higher saturated net photosynthetic rate of flag leaves coincided with the lowered non-photochemical quenching rates in the twice-primed plants under drought stress and in the primed plants during stem elongation under heat stress. Compared to the non-priming treatment, drought priming either applied once or twice alleviated the grain yield reduction by drought stress during grain filling, and priming during the stem elongation stage alleviated yield loss by heat stress at grain filling. The higher concentration of abscisic acid in primed plants under drought stress could contribute to higher grain yield compared to the non-primed plants. Taken together, the results indicate that drought priming during vegetative stages improved tolerance to both drought and heat stress events occurring during grain filling in wheat.

TREE JOINTING AND BRANCH BENDING INFLUENCE ENDOGENOUS LEVELS OF HORMONES AND FLOWERING IN JAPANESE PLUM 'KIYO'

The joint tree training system was developed in Japan as a horticultural intervention to promote flower induction (FI) in fruit trees. In this system, the apical tip of one tree is artificially grafted into the bent main stem of another in a row of three or more trees. The system reportedly facilitates faster establishment of the tree framework leading to faster FI and high productivity of the orchard earlier than those utilizing traditional systems. Plant hormones are putative bio regulators of flower induction and development. However, changes in phytohormone levels as a result of this cultural intervention have not been reported. To investigate this, 5-year old trees of 'Kiyo' Japanese plum (Prunus salicina) in containers were either bent and jointed into a row of three trees (Bent-Joint group), or individually bent (Bent group). Upright individual trees served as control. Young leaves were analyzed for phytohormone content by ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). Our results showed that both the Bent and Bent-Joint groups have significantly lower concentrations of the bioactive gibberellins (i.e., GA1, GA3 and GA4), but higher abscisic acid (ABA) content compared to the control. Consistent with the implicated role of GA as suppressor, and ABA as inducer of FI, both the Bent and Bent-Joint groups registered high flowering rates. Fruit-set was also observed in these groups, while the control had none. The number of new shoots did not significantly vary across treatment groups. Yet control trees, having relatively high bioactive GAs and low ABA contents, exhibited the most vigorous shoot elongation. These findings suggest that the joint tree training system appear to favor FI and fruit-set over vegetative growth that may have resulted from the observed low levels of bioactive GAs and high ABA content.

Abscisic acid inhibits root growth in Arabidopsis through ethylene biosynthesis.

When first discovered in 1963, abscisic acid (ABA) was called abscisin II because it promotes abscission. Later, researchers found that ABA accelerates abscission via ethylene. In Arabidopsis, previous studies have shown that high concentrations of ABA inhibit root growth through ethylene signaling but not ethylene production. In the present study in Arabidopsis, we found that ABA inhibits root growth by promoting ethylene biosynthesis. The ethylene biosynthesis inhibitor L-α-(2-aminoethoxyvinyl)-glycine reduces ABA inhibition of root growth, and multiple mutants of ACS (1-aminocyclopropane-1-carboxylate synthase) are more resistant to ABA in terms of root growth than the wild-type is. Two ABA-activated calcium-dependent protein kinases, CPK4 and CPK11, phosphorylate the C-terminus of ACS6 and increase the stability of ACS6 in ethylene biosynthesis. Plants expressing an ACS6 mutant that mimics the phosphorylated form of ACS6 produce more ethylene than the wild-type. Our results reveal an important mechanism by which ABA promotes ethylene production. This mechanism may be highly conserved among higher plants.

Inhibition of germination of dormant barley (Hordeum vulgare L.) grains by blue light as related to oxygen and hormonal regulation

Germination of primary dormant barley grains is promoted by darkness and temperatures below 20 °C, but is strongly inhibited by blue light. Exposure under blue light at 10 °C for periods longer than five days, results in a progressive inability to germinate in the dark, considered as secondary dormancy. We demonstrate that the inhibitory effect of blue light is reinforced in hypoxia. The inhibitory effect of blue light is associated with an increase in embryo abscisic acid (ABA) content (by 3.5- to 3.8-fold) and embryo sensitivity to both ABA and hypoxia. Analysis of expression of ABA metabolism genes shows that increase in ABA mainly results in a strong increase in HvNCED1 and HvNCED2 expression, and a slight decrease in HvABA8'OH-1. Among the gibberellins (GA) metabolism genes examined, blue light decreases the expression of HvGA3ox2, involved in GA synthesis, increases that of GA2ox3 and GA2ox5, involved in GA catabolism, and reduces the GA signalling evaluated by the HvExpA11 expression. Expression of secondary dormancy is associated with maintenance of high embryo ABA content and a low HvExpA11 expression. The partial reversion of the inhibitory effect of blue light by green light also suggests that cryptochrome might be involved in this hormonal regulation.

Cytokinin-producing, plant growth-promoting rhizobacteria that confer resistance to drought stress in Platycladus orientalis container seedlings

One of the proposed mechanisms through which plant growth-promoting rhizobacteria (PGPR) enhance plant growth is the production of plant growth regulators, especially cytokinin. However, little information is available regarding cytokinin-producing PGPR inoculation on growth and water stress consistence of forest container seedlings under drought condition. This study determined the effects of Bacillus subtilis on hormone concentration, drought resistance, and plant growth under water-stressed conditions. Although no significant difference was observed under well-watered conditions, leaves of inoculated Platycladus orientalis (oriental thuja) seedlings under drought stress had higher relative water content and leaf water potential compared with those of noninoculated ones. Regardless of water supply levels, the root exudates, namely sugars, amino acids and organic acids, significantly increased because of B. subtilis inoculation. Water stress reduced shoot cytokinins by 39.14 %. However, inoculation decreased this deficit to only 10.22 %. The elevated levels of cytokinins in P. orientalis shoot were associated with higher concentration of abscisic acid (ABA). Stomatal conductance was significantly increased by B. subtilis inoculation in well-watered seedlings. However, the promoting effect of cytokinins on stomatal conductance was hampered, possibly by the combined action of elevated cytokinins and ABA. B. subtilis inoculation increased the shoot dry weight of well-watered and drought seedlings by 34.85 and 19.23 %, as well as the root by 15.445 and 13.99 %, respectively. Consequently, the root/shoot ratio significantly decreased, indicative of the greater benefits of PGPR on shoot growth than root. Thus, inoculation of cytokinin-producing PGPR in container seedlings can alleviate the drought stress and interfere with the suppression of shoot growth, showing a real potential to perform as a drought stress inhibitor in arid environments.