种子发育与萌发过程中的程序性细胞死亡

禾谷类种子胚乳发育过程中的程序性细胞死亡(PCD)主要发生在种子成熟期的后期,并伴随着生物合成的停止和自然脱水;乙烯和活性氧促进胚乳发育中的PCD,而ABA起负调节作用。种子萌发过程中糊粉层降解的PCD被GA、Ca^2 和活性氧促进,被ABA和抗氧化剂抑制。种子人工老化和劣变种子萌发过程中可能存在PCD事件,其研究对延长种子的贮藏寿命和提高播种品质具有重要的意义。     

ABA对黑黄檀种子萌发的抑制作用以及其他植物激素对ABA的拮抗作用

以云南特有濒危树种黑黄檀(Dalbergia fusca)的种子为材料,研究了脱落酸(ABA)对种子萌发的抑制作用,以及种子萌发过程中吲哚乙酸(IAA)、赤霉酸(GA_3)、6-苄基腺嘌呤(6-BA)和乙烯利对ABA的拮抗作用.黑黄檀种子萌发的适宜温度为30℃.交替光照(14 h光照和10 h黑暗)以及黑暗对种子萌发没有明显的影响.0.001～0.1 mmol/L ABA不影响种子的萌发率,但降低种子的萌发进程;1 mmol/L和2.5mmol/L ABA显著地抑制种子的萌发率和萌发进程.种子的萌发率不被0.0001～1 mmol/L IAA和GA3、0.0001～0.1 mmol/L 6-BA、以及0.001～10 mmol/L 乙烯利(乙烯供体)的影响,但被1 mmol/L 6-BA抑制.1mmol/L ABA对种子萌发的抑制作用能被0.01～1 mmol/L IAA、0.01～1 mmol/L GA3、0.001～0.1 mmol/L 6-BA和0.1～10 mmol/L乙烯利所拮抗,而且这种拈扰作用与植物激素的类型和浓度有关.0.01 mmol/L 6-BA和0.1 mmol/L乙烯利对l mmol/L ABA抑制作用的拈抗不能被添加0.001 mmol/L IAA或者O.001 mmol/L GA3加成.但0.1 mmol/L 乙烯利对1 mmol/L ABA抑制作用的拮抗能够被添加O.01 mmol/L 6-BA或者0.1 mmol/L 6-BA加成,导致更高的萌发率和幼苗生长.     

科研成果在植物生理学实验教学中应用的一例

＂脱落酸（ABA）对种子发芽率的影响＂是植物生理学中必做的验证性实验,其目的是验证高浓度的ABA会抑制种子萌发。近年来,许多研究表明,盐胁迫下种子萌发受抑制,     

山茱萸种子的休眠原因与萌发条件

山茱萸种子的萌发受到种皮抑制物、胚生理后熟程度以及当年低温的阻抑。种子秋播后需经3个月高温(15～22℃)、2个月低温(5～16℃)的湿沙层积,才能完成生理后熟,于次年春天萌发。并研究了种子层积过程中氧的作用、种皮的单宁和ABA含量、胚乳转化、G6PDH(6—磷酸葡萄糖脱氢酶)和 6PGDH(6—磷酸葡萄糖酸脱氢酶)与萌发的关系。     

6-BA拮抗脱落酸缓解渗透胁迫对种子萌发的抑制

细胞分裂素促进细胞分裂、芽的分化,拮抗脱落酸抑制的种子萌发,而细胞分裂素合成基因Ipt84在种子萌发过程中发挥重要的作用。本文分别用120mmol·L-1 NaCl和240mmol·L-1 甘露醇模拟盐和干旱胁迫处理拟南芥种子,探讨6一BA拮抗ABA对其抑制种子萌发和萌发后生长的影响。结果表明,细胞分裂素合成相关突变体ipt6-1、ipt6-2、ipt8．1和ipt8-2的种子萌发和生长可被NaCl和甘露醇显著抑制;而ABA合成相关突变体aba2-1对相同浓度NaCl和甘露醇的处理表现相对不敏感。进一步研究发现添加外源6一BA可恢复ipt6-1、ipt6-2、ipt8-1和ipt8—2的相关敏感表型,并且随6-BA浓度的增加,恢复效果也愈趋明显。     

ABA 对黑黄檀种子萌发的抑制作用以及其他植物激素对ABA 的拮抗作用

以云南特有濒危树种黑黄檀( Dalbergia fusca) 的种子为材料, 研究了脱落酸(ABA) 对种子萌发的抑制作用, 以及种子萌发过程中吲哚乙酸( IAA) 、赤霉酸(GA3 )、6-苄基腺嘌呤(6-BA) 和乙烯利对ABA的拮抗作用。黑黄檀种子萌发的适宜温度为30℃。交替光照(14 h 光照和10 h 黑暗) 以及黑暗对种子萌发没有明显的影响。0 . 001～0 . 1 mmol/L ABA 不影响种子的萌发率, 但降低种子的萌发进程; 1 mmol􊄯L 和2 . 5mmo􊄯l L ABA 显著地抑制种子的萌发率和萌发进程。种子的萌发率不被0 . 0001 ～ 1 mmo􊄯l L IAA 和GA3 、0 . 0001～0 . 1 mmol/L 6-BA、以及0 . 001～10 mmol/L 乙烯利( 乙烯供体) 的影响,但被1 mmol􊄯L 6-BA 抑制。1mmol/L ABA 对种子萌发的抑制作用能被0 . 01～1 mmol/L IAA、0 . 01～1 mmol/L GA3 、0 . 001～0 .1 mmol/L 6-BA 和0 . 1～10 mmol􊄯L 乙烯利所拮抗, 而且这种拮抗作用与植物激素的类型和浓度有关。0. 01 mmol/L 6-BA 和0 . 1 mmol/L 乙烯利对1mmol/L ABA 抑制作用的拮抗不能被添加0 . 001 mmol/L IAA 或者0 .001 mmol/L GA3 加成。但0 . 1mmol/L 乙烯利对1 mmol/L ABA 抑制作用的拮抗能够被添加0 . 01 mmol/L 6-BA 或者0 .1 mmol/L 6-BA 加成, 导致更高的萌发率和幼苗生长。     

脱落酸调控种子萌发和休眠的研究进展

脱落酸(abscisic acid,ABA)是重要的植物激素之一。在促进种子休眠、抑制种子萌发的过程中,ABA发挥着举足轻重的调节作用。种子的萌发始于种子的吸水膨胀,止于胚轴的伸长,是高等植物生命周期中最为关键的阶段。在新生个体萌动的阶段,ABA与其他激素协同互作调控着这一重要的发育过程。现围绕ABA在种子休眠、萌发以及萌发后幼苗生长过程中的信号转导机制,着重从ABA与细胞分裂素和赤霉素等相互作用调控种子萌发的角度,概述相关的最新研究进展,并对今后的研究方向作出展望。     

过表达VHA-c3基因拟南芥对黑暗、ABA与糖的响应

为研究液泡H+-ATPase c亚基基因(VHA-c3)在植物生长发育及非生物胁迫应答过程中的作用,构建了VHA-c3过表达载体转化拟南芥,获得过表达VHA-c3的转基因纯合体植株,采用半定量RT-PCR技术分析了转基因拟南芥中VHA-c3的表达量,然后对转基因拟南芥进行暗培养、ABA和糖处理。结果获得6个T2代株系转基因纯合体株系,其m RNA表达量均高于对照;黑暗条件下,5个VHA-c3转基因株系的根长变短;在正常光照下,3个转基因株系主根伸长和子叶的展开以及5个转基因株系的种子萌发对ABA的抑制不敏感;分别有5个和6个转基因株系的种子萌发对葡萄糖和蔗糖的抑制不敏感。推测VHA-c3可能影响根细胞的扩展,并可能参与ABA和糖介导的信号转导途径。     

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

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、10.0μmol/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5.0μmol/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。     

光信号与激素调控种子休眠和萌发研究进展

休眠是种子植物在长期进化过程中产生的适应性性状, 通过抑制种子在不适宜的环境中萌发进而保证植物能够在逆境中生存。此外, 休眠有助于种子的长距离运输和扩散, 因此休眠对种子延续和物种保存具有重要意义。种子由休眠向萌发的发育转变不仅关系到物种的繁衍, 而且对保证农业生产中作物的产量和品质也具有重要作用。种子的休眠和萌发受到内源激素和外源光信号的共同调控。其中, 外源光信号主要通过调控内源ABA和GA的生物合成及信号转导进而调控种子休眠和萌发。该文系统综述了外源光信号和内源激素调控种子休眠和萌发的作用通路以及两类信号通路之间的交互作用, 旨在为农业生产中利用光和激素调控种子休眠与萌发提供参考。     

The regulator of G-protein signaling proteins involved in sugar and abscisic acid signaling in Arabidopsis seed germination

The regulator of G-protein signaling (RGS) proteins, recently identified in Arabidopsis (Arabidopsis thaliana; named as AtRGS1), has a predicted seven-transmembrane structure as well as an RGS box with GTPase-accelerating activity and thus desensitizes the G-protein-mediated signaling. The roles of AtRGS1 proteins in Arabidopsis seed germination and their possible interactions with sugars and abscisic acid (ABA) were investigated in this study. Using seeds that carry a null mutation in the genes encoding RGS protein (AtRGS1) and the alpha-subunit (AtGPA1) of the G protein in Arabidopsis (named rgs1-2 and gpa1-3, respectively), our genetic evidence proved the involvement of the AtRGS1 protein in the modulation of seed germination. In contrast to wild-type Columbia-0 and gpa1-3, stratification was found not to be required and the after-ripening process had no effect on the rgs1-2 seed germination. In addition, rgs1-2 seed germination was insensitive to glucose (Glc) and sucrose. The insensitivities of rgs1-2 to Glc and sucrose were not due to a possible osmotic stress because the germination of rgs1-2 mutant seeds showed the same response as those of gpa1-3 mutants and wild type when treated with the same concentrations of mannitol and sorbitol. The gpa1-3 seed germination was hypersensitive while rgs1-2 was less sensitive to exogenous ABA. The different responses to ABA largely diminished and the inhibitory effects on seed germination by exogenous ABA and Glc were markedly alleviated when endogenous ABA biosynthesis was inhibited. Hypersensitive responses of seed germination to both Glc and ABA were also observed in the overexpressor of AtRGS1. Analysis of the active endogenous ABA levels and the expression of NCED3 and ABA2 genes showed that Glc significantly stimulated the ABA biosynthesis and increased the expression of NCED3 and ABA2 genes in germinating Columbia seeds, but not in rgs1-2 mutant seeds. These data suggest that AtRGS1 proteins are involved in the regulation of seed germination. The hyposensitivity of rgs1-2 mutant seed germination to Glc might be the result of the impairment of ABA biosynthesis during seed germination.     

AtMKK1 and AtMPK6 are involved in abscisic acid and sugar signaling in <Emphasis Type="Italic">Arabidopsis</Emphasis> seed germination

Abscisic acid (ABA) and sugars have been well established to be crucial factors controlling seed germination of Arabidopsis. Here we demonstrate that AtMKK1 and AtMPK6 are both critical signals involved in ABA and sugar-regulated seed germination. Wild type plants depended on stratification and after-ripening for seed germination, whereas this dependence on either stratification or after-ripening was not required for mutants of mkk1 and mpk6 as well as their double mutant mkk1 mpk6. While seed germination of wild type plants was sensitively inhibited by ABA and glucose, mkk1, mpk6 and mkk1 mpk6 were all strongly resistant to ABA or glucose treatments, and in contrast, plants overexpressing MKK1 or MPK6 were super-sensitive to ABA and glucose. Glucose treatment significantly induced increases in MKK1 and MPK6 activities. These results clearly indicate that MKK1 and MPK6 are involved in the ABA and sugar signaling in the process of seed germination. Further experiments showed that glucose was capable of inducing ABA biosynthesis by up-regulating NCED3 and ABA2, and furthermore, this up-regulation of NCED3 and ABA2 was arrested in the mkk1 mpk6 double mutant, indicating that the inhibition of seed germination by glucose is potentially resulted from sugar-induced up-regulation of the ABA level. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Ectopic expression of ABSCISIC ACID 2/GLUCOSE INSENSITIVE 1 in Arabidopsis promotes seed dormancy and stress tolerance

Abscisic acid (ABA) is an important phytohormone that plays a critical role in seed development, dormancy, and stress tolerance. 9-cis-Epoxycarotenoid dioxygenase is the key enzyme controlling ABA biosynthesis and stress tolerance. In this study, we investigated the effect of ectopic expression of another ABA biosynthesis gene, ABA2 (or GLUCOSE INSENSITIVE 1 [GIN1]) encoding a short-chain dehydrogenase/reductase in Arabidopsis (Arabidopsis thaliana). We show that ABA2-overexpressing transgenic plants with elevated ABA levels exhibited seed germination delay and more tolerance to salinity than wild type when grown on agar plates and/or in soil. However, the germination delay was abolished in transgenic plants showing ABA levels over 2-fold higher than that of wild type grown on 250 mm NaCl. The data suggest that there are distinct mechanisms underlying ABA-mediated inhibition of seed germination under diverse stress. The ABA-deficient mutant aba2, with a shorter primary root, can be restored to normal root growth by exogenous application of ABA, whereas transgenic plants overexpressing ABA2 showed normal root growth. The data reflect that the basal levels of ABA are essential for maintaining normal primary root elongation. Furthermore, analysis of ABA2 promoter activity with ABA2::beta-glucuronidase transgenic plants revealed that the promoter activity was enhanced by multiple prolonged stresses, such as drought, salinity, cold, and flooding, but not by short-term stress treatments. Coincidently, prolonged drought stress treatment led to the up-regulation of ABA biosynthetic and sugar-related genes. Thus, the data support ABA2 as a late expression gene that might have a fine-tuning function in mediating ABA biosynthesis through primary metabolic changes in response to stress.     

AhCYCB1基因的克隆和在ABA抑制花生侧根发生过程中的表达

根据水稻、拟南芥和玉米等植株的CYCB基因序列设计引物,以花生根系成熟区总RNA逆转录得到的cDNA为模板,用PCR扩增克隆花生CYCB1基因片段,命名为AhCYCB1（GenBank登录号为GQ868755）。该基因编码的蛋白具有CYCB1蛋白序列的特征区,与拟南芥的AtCYCB1蛋白聚类关系最近。半定量RT-PCR分析表明,ABA处理后,侧根起始部位的AhCY-CB1基因表达水平降低,ABA合成抑制剂萘普生（naproxen）处理使AhCYCB1基因表达水平明显上调。推测ABA抑制侧根发生与其降低侧根发生部位由G2期进入M期的细胞数目有关。     

Molecular identification of zeaxanthin epoxidase of Nicotiana plumbaginifolia, a gene involved in abscisic acid biosynthesis and corresponding to the ABA locus of Arabidopsis thaliana.

Abscisic acid (ABA) is a plant hormone which plays an important role in seed development and dormancy and in plant response to environmental stresses. An ABA-deficient mutant of Nicotiana plumbaginifolia, aba2, was isolated by transposon tagging using the maize Activator transposon. The aba2 mutant exhibits precocious seed germination and a severe wilty phenotype. The mutant is impaired in the first step of the ABA biosynthesis pathway, the zeaxanthin epoxidation reaction. ABA2 cDNA is able to complement N.plumbaginifolia aba2 and Arabidopsis thaliana aba mutations indicating that these mutants are homologous. ABA2 cDNA encodes a chloroplast-imported protein of 72.5 kDa, sharing similarities with different mono-oxigenases and oxidases of bacterial origin and having an ADP-binding fold and an FAD-binding domain. ABA2 protein, produced in Escherichia coli, exhibits in vitro zeaxanthin epoxidase activity. This is the first report of the isolation of a gene of the ABA biosynthetic pathway. The molecular identification of ABA2 opens the possibility to study the regulation of ABA biosynthesis and its cellular location.     

Proteomic analysis of seed dormancy in Arabidopsis

The mechanisms controlling seed dormancy in Arabidopsis (Arabidopsis thaliana) have been characterized by proteomics using the dormant (D) accession Cvi originating from the Cape Verde Islands. Comparative studies carried out with freshly harvested dormant and after-ripened non-dormant (ND) seeds revealed a specific differential accumulation of 32 proteins. The data suggested that proteins associated with metabolic functions potentially involved in germination can accumulate during after-ripening in the dry state leading to dormancy release. Exogenous application of abscisic acid (ABA) to ND seeds strongly impeded their germination, which physiologically mimicked the behavior of D imbibed seeds. This application resulted in an alteration of the accumulation pattern of 71 proteins. There was a strong down-accumulation of a major part (90%) of these proteins, which were involved mainly in energetic and protein metabolisms. This feature suggested that exogenous ABA triggers proteolytic mechanisms in imbibed seeds. An analysis of de novo protein synthesis by two-dimensional gel electrophoresis in the presence of [(35)S]-methionine disclosed that exogenous ABA does not impede protein biosynthesis during imbibition. Furthermore, imbibed D seeds proved competent for de novo protein synthesis, demonstrating that impediment of protein translation was not the cause of the observed block of seed germination. However, the two-dimensional protein profiles were markedly different from those obtained with the ND seeds imbibed in ABA. Altogether, the data showed that the mechanisms blocking germination of the ND seeds by ABA application are different from those preventing germination of the D seeds imbibed in basal medium.