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Progress in Seed Dormancy and Germination of Arabidopsis Mutants

Weiqing Wang,Hongyan Cheng,

植物学报 , 2006,
Abstract: Seed dormancy and germination are complicated processes, and their mechanisms to date are still unclear. However, some genes correlated with seed dormancy and germination have been identified from Arabidopsis mutants, which would be helpful in understanding the mechanisms of seed germination and dormancy. Gibberellic acid (GA) is one of the key factors promoting seed germination. Genes such as RGL, SPY, GCR, SLY and GAR are involved in the GA promotion of seed germination, whereas ABI1, ABI2, ABI3, ABI4, ABI5, FUS3, LEC, MARD and CIPK are relevant to the induction of abscisic acid (ABA) in seed dormancy. Research results involving the ethylene mutants of ein, etr, and ctr and the brassinosteroid mutants det and bri indicated that both ethylene and brassinosteroids promote seed germination via counteracting the inhibitory effects of ABA. The phytochromes PhyA, PhyB, PhyC, PhyD and PhyE are light receptors that regulate the expression of other germination-related genes by phosphorylation. Nitrogenous compounds could release dormancy in a way depending on nitric oxide.
A rapid and robust method for simultaneously measuring changes in the phytohormones ABA, JA and SA in plants following biotic and abiotic stress
Silvia Forcat, Mark H Bennett, John W Mansfield, Murray R Grant
Plant Methods , 2008, DOI: 10.1186/1746-4811-4-16
Abstract: Phytohormones play an important role in mediating host responses to various biotic and abiotic stresses such as pathogen challenge, insect herbivory, drought, cold and heat stress. Traditionally, salicylic acid (SA) and jasmonic acid (JA) have been, respectively, associated with resistance to biotrophic and necrotrophic pathogens (reviewed in [1,2]. Although classical SA and JA responsive molecular markers indicate that these phytohormones function antagonistically, recent studies suggest that both the timing and amplitude of hormonal signals play key roles in determining the final pathological phenotype [3,4].Emerging evidence suggests that a key strategy of plant pathogens is to modify plant hormone levels to promote pathogenicity. Consequently, pathogens have evolved complex repertoires of effector proteins whose functions include modulation of basal phytohormone levels during development of disease. For example, during foliar infection, the hemibiotrophic bacterial pathogen, Pseudomonas syringae pv. tomato DC3000, delivers ~30 effector proteins into the plant cell [5]. Experimental data suggest they act with a surprising degree of redundancy to modify host signalling pathways, and one clear strategy is to suppress or modify plant hormone responses [6,7].Recently, the stress hormone, abscisic acid (ABA), better known for its role in response to drought stress and maintenance of seed dormancy (reviewed by (8) has been demonstrated to influence plant pathogen interactions [9-12]. Emerging evidence suggests there are most likely antagonistic interactions between ABA and, JA/ET (ethylene) [13] or SA, signalling pathways depending upon the lifestyle of the infecting pathogen. Thus it is important to be able to measure changes in endogenous concentrations of these hormones at different stages of the infection process. Moreover there is an increasing interest in crosstalk between biotic and abiotic stress pathways [14], how plants prioritize their responses under a give
Sequence Variation and Expression Analysis of Seed Dormancy- and Germination-Associated ABA- and GA-Related Genes in Rice Cultivars  [PDF]
Fei Liu,Hangxiao Zhang,Gang Wu,Lili Hao,Jun Yu
Frontiers in Plant Science , 2011, DOI: 10.3389/fpls.2011.00017
Abstract: Abscisic acid (ABA) and Gibberellic acid (GA) play key roles in regulating seed dormancy and germination. First, when examining germination of different rice cultivars, we found that their germination timing and dormancy status are rather distinct, coupled with different GA/ABA ratio. Second, we studied genomic sequences of ABA and GA dormancy- and germination-associated genes in rice and discovered single nucleotide polymorphisms and insertions/deletions (Indels) in both coding and regulatory sequences. We aligned all these variations to the genome assemblies of 9311 and PA64s and demonstrated their relevance to seed dormancy both quantitatively and qualitatively based on gene expression data. Third, we surveyed and compared differentially expressed genes in dry seeds between 9311 and PA64s to show that these differentially expressed genes may play roles in seed dormancy and germination.
Cloning of 9-cis-epoxycarotenoid dioxygenase (NCED) gene encoding a key enzyme during abscisic acid (ABA) biosynthesis and ABA-regulated ethylene production in detached young persimmon calyx
Ping Leng,GuangLian Zhang,XiangXin Li,LiangHe Wang,ZhongMing Zheng
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0486-7
Abstract: Unlike the typical climacteric fruits, persimmons (Diospyros kaki Thunb.) produce higher levels of ethylene when they are detached from trees at a younger stage. In order to obtain detailed information on the role of abscisic acid (ABA) in ripening, we cloned the DKNCED1, DKACS2, and DKACO1 genes from the calyx. Water loss was first noted in the calyx lobe, and DKNCED1 was highly expressed 1 d after the fruits were detached, coinciding with an increase in the ABA content. Then, the DKACS2 and DKACO1 genes were expressed after some delay. In the calyx, the ABA peak was observed 2 d after the fruits were harvested, and this peak preceded the ethylene peak observed on day 3. The fruit firmness rapidly decreased on day 4, and the fruits softened completely 6 d after they were harvested. The increases in the expressions of ABA, ethylene, and the genes in the calyxes occurred earlier than the corresponding increases in the pulp, although the 3 increases occurred on different days. Exogenous ABA treatment increased ABA concentration, induced expression of both ACS and ACO, and promoted ethylene synthesis and young-fruit softening; by contrast, treatment with NDGA inhibited the gene expressions and ethylene synthesis and delayed young-fruit softening. These results indicate that ethylene biosynthesis in the detached young persimmon fruits is initially triggered by ABA, which is induced by water loss in the calyx, through the induction of DKACS2 and DKACO1 expressions. The ethylene produced in the calyx subsequently diffuses into the pulp tissue, where it induces autocatalytic ethylene biosynthesis, resulting in an abrupt increase in ethylene production.
ABI4 Regulates Primary Seed Dormancy by Regulating the Biogenesis of Abscisic Acid and Gibberellins in Arabidopsis  [PDF]
Kai Shu,Huawei Zhang,Shengfu Wang,Mingluan Chen,Yaorong Wu,Sanyuan Tang,Chunyan Liu,Yuqi Feng,Xiaofeng Cao,Qi Xie
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003577
Abstract: Seed dormancy is an important economic trait for agricultural production. Abscisic acid (ABA) and Gibberellins (GA) are the primary factors that regulate the transition from dormancy to germination, and they regulate this process antagonistically. The detailed regulatory mechanism involving crosstalk between ABA and GA, which underlies seed dormancy, requires further elucidation. Here, we report that ABI4 positively regulates primary seed dormancy, while negatively regulating cotyledon greening, by mediating the biogenesis of ABA and GA. Seeds of the Arabidopsis abi4 mutant that were subjected to short-term storage (one or two weeks) germinated significantly more quickly than Wild-Type (WT), and abi4 cotyledons greened markedly more quickly than WT, while the rates of germination and greening were comparable when the seeds were subjected to longer-term storage (six months). The ABA content of dry abi4 seeds was remarkably lower than that of WT, but the amounts were comparable after stratification. Consistently, the GA level of abi4 seeds was increased compared to WT. Further analysis showed that abi4 was resistant to treatment with paclobutrazol (PAC), a GA biosynthesis inhibitor, during germination, while OE-ABI4 was sensitive to PAC, and exogenous GA rescued the delayed germination phenotype of OE-ABI4. Analysis by qRT-PCR showed that the expression of genes involved in ABA and GA metabolism in dry and germinating seeds corresponded to hormonal measurements. Moreover, chromatin immunoprecipitation qPCR (ChIP-qPCR) and transient expression analysis showed that ABI4 repressed CYP707A1 and CYP707A2 expression by directly binding to those promoters, and the ABI4 binding elements are essential for this repression. Accordingly, further genetic analysis showed that abi4 recovered the delayed germination phenotype of cyp707a1 and cyp707a2 and further, rescued the non-germinating phenotype of ga1-t. Taken together, this study suggests that ABI4 is a key factor that regulates primary seed dormancy by mediating the balance between ABA and GA biogenesis.
Ethylene-induced nitric oxide production and stomatal closure in Arabidopsis thaliana depending on changes in cytosolic pH
Jing Liu,GuoHua Liu,LiXia Hou,Xin Liu
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-010-4033-3
Abstract: We investigated changes in cytosolic pH and nitric oxide (NO) during ethylene-induced stomatal closure in Arabidopsis thaliana using pharmacological, laser scanning confocal microscopy (LSCM), and spectrophotography techniques. Treatment with ethephon (a direct source of ethylene when applied to plants) and 1-aminocycloaminopropane-1-carboxylic acid (ACC, an ethylene precursor) resulted in a rapid accumulation of NO and cytosolic alkalinization in guard cells. Acetic acid (a weak acid) and sodium orthovanadate (NaVO3; a plasmalemma H+-ATPase inhibitor) reduced stomatal closure induced by ethylene and blocked ethylene-induced activity of nitrate reductase. However, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), a NO scavenger, had no effect. These results suggest that NO production is downstream of the rise in cytosolic pH in A. thaliana.
Compound stress response in stomatal closure: a mathematical model of ABA and ethylene interaction in guard cells
Mariano Beguerisse-D?az, Mercedes C Hernández-Gómez, Alessandro M Lizzul, Mauricio Barahona, Radhika Desikan
BMC Systems Biology , 2012, DOI: 10.1186/1752-0509-6-146
Abstract: Toshed light on this unexplained behaviour, we have collected time course measurements of stomatal aperture and hydrogen peroxide production in Arabidopsis thaliana guard cells treated with abscisic acid, ethylene, and a combination of both. Our experiments show that stomatal closure is linked to sustained high levels of hydrogen peroxide in guard cells. When treated with a combined dose of abscisic acid and ethylene, guard cells exhibit increased antioxidant activity that reduces hydrogen peroxide levels and precludes closure. We construct a simplified model of stomatal closure derived from known biochemical pathways that captures the experimentally observed behaviour.Our experiments and modelling results suggest a distinct role for two antioxidant mechanisms during stomatal closure: a slower, delayed response activated by a single stimulus (abscisic acid ‘or’ ethylene) and another more rapid ‘and’ mechanism that is only activated when both stimuli are present. Our model indicates that the presence of this rapid ‘and’ mechanism in the antioxidant response is key to explain the lack of closure under a combined stimulus.Stomata are tiny pores located mainly in the lower epidermis of plant leaves. Each stoma is formed by two guard cells attached to each other by their extremes. When the guard cells are turgid, due to their vacuoles being full of water, the pore opens (Figure 1A). When the vacuoles are emptied and water exits the cells, the guard cells become flaccid and the pore closes (Figure 1B) [1]. Loss of turgor pressure (and the resulting closure of the stomatal pore) is a consequence of the efflux of ions out of the cell. Ion efflux may be caused by a variety of stimuli including different light conditions and atmospheric carbon dioxide (CO2) levels, or signalling hormones such as abscisic acid (ABA) and ethylene [2,3]. Open pores allow the plant to absorb CO2 from the air to perform photosynthesis and to release oxygen and water into the atmosphere. If the por
Relationship between ABA and ethylene content and fruit ripening during fig fruit development

- , 2016,
Abstract: 为研究无花果果实发育过程中ABA和乙烯含量与果实成熟的关系,以玛斯义陶芬(Masui dauphine)无花果果实为试材,对果实发育过程中呼吸速率和乙烯释放量及可溶性糖、淀粉和ABA含量进行了研究。结果表明:无花果果实发育分3个时期,第1个快速生长期(时期Ⅰ)、缓慢生长期(时期Ⅱ)和第2个快速生长期(时期Ⅲ),在缓慢生长期和第2个快速生长期之间为果实发育的转折期“始熟期”。始熟期后果实淀粉分解,大量积累葡萄糖和果糖,果实快速进入成熟期。无花果果实发育过程中ABA含量整体呈下降趋势,乙烯释放量随着果实发育逐渐增加,在始熟期和呼吸速率同步出现一个高峰。结果表明无花果果实是呼吸跃变型果实,乙烯诱导果实发生一系列生理生化变化,促使无花果果实成熟。
To study the relationship between ABA and ethylene content and fruit ripening during the development of fig fruit,fig (Ficus carica L.) cultivar ‘Masui Dauphine’ was used in this study.The changes of respiratory rate,soluble sugar content,starch content,ABA level and ethylene production level were examined.The results showed that:The development of fig fruit was comprised of three phases,phase Ⅰ (the first rapid growth stage),phase Ⅱ (the lag phase of growth),and phase Ⅲ (the second rapid growth stage).The transition from phase Ⅱ to phase Ⅲ was the onset of ripening.After the onset of ripening,starch content of fig fruit was decreased,but a large amount of glucose and fructose were accumulated,and the fruit matured quickly.There was an decrease in ABA content during ripening of fig fruits.But there was an increase in ethylene production during fig fruits ripening,and during the onset of ripening a respiratory climacteric rise was concomitant with a sudden burst of endogenous ethylene production.These results suggested that fig fruit is a typical climacteric fruit.Ethylene initiated a chain of metabolic and physiological events which lead to fig fruit ripening.
Hydrogen sulfide induced by nitric oxide mediates ethylene-induced stomatal closure of Arabidopsis thaliana
Jing Liu,LiXia Hou,GuoHua Liu,Xin Liu,XueChen Wang
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4819-y
Abstract: Pharmacological, laser scanning confocal microscopic (LSCM), real-time PCR and spectrophotographic approaches are used to study the roles of hydrogen sulfide (H2S) and nitric oxide (NO) in signaling transduction of stomatal movement response to ethylene in Arabidopsis thaliana. In the present study, inhibitors of H2S synthesis were found to block ethylene-induced stomatal closure of Arabidopsis. Treatment with ethylene induced H2S generation and increased L-/D-cysteine desulfhydrase (pyridoxalphosphate-dependent enzyme) activity in leaves. Quantitative PCR analysis showed AtL-CDes and AtD-CDes transcripts were induced by ethylene. It is suggested that ethylene-induced H2S levels and L-/D-cysteine desulfhydrase activity decreased when NO was compromised. The data clearly show that ethylene was able to induce H2S generation and stomatal closure in Atnoa1 plants, but failed in the Atnia1,nia2 mutant. Inhibitors of H2S synthesis had no effect on ethylene-induced NO accumulation and nitrate reductase (NR) activity in guard cells or leaves of Arabidopsis, whereas ethylene was able to induce NO synthesis. Therefore, we conclude that H2S and NO are involved in the signal transduction pathway of ethylene-induced stomatal closure. In Arabidopsis, H2S may represent a novel downstream indicator of NO during ethylene-induced stomatal movement.
Disturbed Local Auxin Homeostasis Enhances Cellular Anisotropy and Reveals Alternative Wiring of Auxin-ethylene Crosstalk in Brachypodium distachyon Seminal Roots  [PDF]
David Pacheco-Villalobos,Martial Sankar,Karin Ljung,Christian S. Hardtke
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003564
Abstract: Observations gained from model organisms are essential, yet it remains unclear to which degree they are applicable to distant relatives. For example, in the dicotyledon Arabidopsis thaliana (Arabidopsis), auxin biosynthesis via indole-3-pyruvic acid (IPA) is essential for root development and requires redundant TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1 (TAA1) and TAA1-RELATED (TAR) genes. A promoter T-DNA insertion in the monocotyledon Brachypodium distachyon (Brachypodium) TAR2-LIKE gene (BdTAR2L) severely down-regulates expression, suggesting reduced tryptophan aminotransferase activity in this mutant, which thus represents a hypomorphic Bdtar2l allele (Bdtar2lhypo). Counterintuitive however, Bdtar2lhypo mutants display dramatically elongated seminal roots because of enhanced cell elongation. This phenotype is also observed in another, stronger Bdtar2l allele and can be mimicked by treating wild type with L-kynerunine, a specific TAA1/TAR inhibitor. Surprisingly, L-kynerunine-treated as well as Bdtar2l roots display elevated rather than reduced auxin levels. This does not appear to result from compensation by alternative auxin biosynthesis pathways. Rather, expression of YUCCA genes, which are rate-limiting for conversion of IPA to auxin, is increased in Bdtar2l mutants. Consistent with suppression of Bdtar2lhypo root phenotypes upon application of the ethylene precursor 1-aminocyclopropane-1-carboxylic-acid (ACC), BdYUCCA genes are down-regulated upon ACC treatment. Moreover, they are up-regulated in a downstream ethylene-signaling component homolog mutant, Bd ethylene insensitive 2-like 1, which also displays a Bdtar2l root phenotype. In summary, Bdtar2l phenotypes contrast with gradually reduced root growth and auxin levels described for Arabidopsis taa1/tar mutants. This could be explained if in Brachypodium, ethylene inhibits the rate-limiting step of auxin biosynthesis in an IPA-dependent manner to confer auxin levels that are sub-optimal for root cell elongation, as suggested by our observations. Thus, our results reveal a delicate homeostasis of local auxin and ethylene activity to control cell elongation in Brachypodium roots and suggest alternative wiring of auxin-ethylene crosstalk as compared to Arabidopsis.
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