拟南芥莲座叶芥子油苷含量对水分胁迫的响应

芥子油苷(glucosinolates)是十字花科植物中一类含氮、含硫的次生代谢产物,与其水解产物在植物防御功能中有重要意义且与环境因子关系密切.通过控制供水的方式对营养生长时期的拟南芥幼苗进行水分胁迫,观察了土壤自然干旱对营养生长时期拟南芥莲座叶芥子油苷含量及组成的影响.结果表明,土壤自然干旱处理下,拟南芥莲座叶的芥子油苷总量从处理3 d起低于对照,且随着处理天数的增加与对照组的差异逐渐增大,脂肪族芥子油苷的响应均比较明显,与芥子油苷总量的变化趋势基本一致,而吲哚族芥子油苷对水分胁迫则不敏感.脂肪族中的4-甲基亚磺酰丁基芥子油苷(4-methylsulphinylbutyl GS,4MSOB)占脂肪族芥子油苷的比例最大,它的含量变化成为影响莲座叶中芥子油苷组合模式的主导因素.     

机械损伤对拟南芥莲座叶芥子油苷含量和组成的影响

植物可以利用体内次生代谢产物的变化来抵御昆虫取食和机械损伤.芥子油苷是拟南芥的主要次生代谢产物.通过剪刀剪取叶片(40%面积)对温室培养的拟南芥幼苗莲座叶进行机械损伤处理,观察机械损伤后8个时间点拟南芥叶片中不同种类芥子油苷含量和组合模式的变化.结果表明机械损伤后3 h叶片中芥子油苷总含量开始明显上升,脂肪族和吲哚族芥子油苷含量在损伤后3 h也都显著高于损伤前.在检测到的12种芥子油苷中,4-甲基亚磺酰丁基芥子油苷(4-methylsulphinylbutyl GS,4MSOB)的含量最多,占芥子油苷总量的48.5%,并且在损伤3 h后含量增加.4MSOB含量的变化成为影响莲座叶中芥子油苷组合模式的主导因素.其它各种芥子油苷在损伤后不同时间点的变化也存在差异.     

COI1参与茉莉酸调控拟南芥吲哚族芥子油苷生物合成过程

芥子油苷是一类具有防御作用的植物次生代谢产物,外源激素茉莉酸对吲哚族芥子油苷的合成具有强烈的诱导作用,但茉莉酸调控吲哚族芥子油苷生物合成的分子机制并不清楚。以模式植物拟南芥(Arabidopsis thaliana)的野生型和coi1-22、coi1-23两种突变体为研究材料,通过茉莉酸甲酯(MeJA)处理,比较了拟南芥野生型和coi1突变体植株吲哚族芥子油苷含量、吲哚族芥子油苷合成前体色氨酸的生物合成基因(ASA1、TSA1和TSB1)、吲哚族芥子油苷生物合成基因(CYP79B2、CYP79B3和CYP83B1)及调控基因(MYB34和MYB51)的表达对MeJA的响应差异,由此确定茉莉酸信号通过COI1蛋白调控吲哚族芥子油苷生物合成,即茉莉酸信号通过信号开关COI1蛋白作用于转录因子MYB34和MYB51,进而调控吲哚族芥子油苷合成基因CYP79B2、CYP79B3、CYP83B1和前体色氨酸的合成基因ASA1、TSA1、TSB1。并且推断,COI1功能缺失后,茉莉酸信号可能通过其他未知调控因子或调控途径激活MYB34转录因子从而调控下游基因表达。     

flg22诱导的拟南芥转录组分析及芥子油苷代谢途径的变化

flg22是细菌鞭毛蛋白N端的一段保守性极高的区域,能够诱导植物天然的免疫反应,为全面了解植物在受到细菌性病原菌侵害后的系统响应,利用Illumina Hiseq2000对flg22处理和未处理的拟南芥幼苗进行转录组测序。对两组数据进行差异表达分析,共获得1 200个差异表达基因,包括290个下调基因和910个上调基因。对差异表达基因进行GO富集分析和KEGG pathway富集分析,结果显示,flg22处理后,拟南芥在能量代谢、氨基酸代谢及次生代谢产物的生物合成等方面产生了巨大变化。芥子油苷是一类在植物防御病原菌的天然免疫反应中起重要作用的次生代谢产物,因此对芥子油苷代谢途径的变化进行了深入分析。根据测序结果,Flg22处理后吲哚族芥子油苷合成途径的基因表达水平显著提高,而脂肪族芥子油苷代谢途径几乎没有变化,进一步对吲哚族芥子油苷合成途径的关键酶基因进行Real Time RT-PCR的分析,验证了测序结果的正确性,证明了吲哚族芥子油苷在植物抗病防御反应中的重要作用。这为深入理解病原菌诱导的植物防御性反应及吲哚族芥子油苷的抗病机制提供了大量参考数据。     

盐胁迫盐芥和拟南芥褪黑素含量及合成相关基因表达模式分析

盐生植物盐芥（Eutrema salsugineum）耐盐适应性强且具备模式植物特征,是研究植物逆境适应机理的理想材料。作为一种多功能的激素信号分子,褪黑素在盐芥耐盐性中的作用仍不清楚。本研究以盐芥为主要材料,以拟南芥做对比,主要通过褪黑素酶联免疫以及实时荧光定量PCR分析,比较了二者在不同组织中褪黑素的积累和在响应盐胁迫过程中褪黑素合成、相关基因的表达模式以及外源褪黑素处理对其盐应答表型的影响。结果显示,两种植物的褪黑素合成均在幼叶中最高,盐芥本底褪黑素合成水平显著高于拟南芥,且盐胁迫诱导了两种植物中的褪黑素含量,但不同于盐芥,拟南芥在处理7 d后褪黑素合成明显下降。通过序列比对发现在不同植物中,盐芥和拟南芥褪黑素合成相关基因的亲缘关系较近。盐应答表达分析显示,盐芥SNAT1、ASMT和COMT在盐处理3 d表达上调,而拟南芥中的相关基因在处理1 d和3 d后受盐诱导,7 d后拟南芥中表达下降而盐芥中则无明显变化,表明两种植物相关基因响应盐信号的表达变化存在差异。此外,外源褪黑素处理明显缓解了两种植物在盐逆境下的胁迫表型。综上,褪黑素有效贡献于盐芥抗盐性,参与调节盐芥和拟南芥的耐盐适...     

植物激素与芥子油苷在生物合成上的相互作用

植物激素在植物的生长发育中起着关键性作用,芥子油苷是一类重要的次生代谢物质。植物激素与芥子油苷之间存在复杂的相互作用。生长素与吲哚类芥子油苷在生物合成上存在着相互作用。植物防卫信号分子与芥子油苷之间也存在相互作用,茉莉酸强烈诱导吲哚类芥子油苷生物合成相关基因CYP7982和CYP7983的表达,从而诱导吲哚-3-甲基芥子油苷和N-甲氧吲哚-3-甲基芥子油苷等吲哚类芥子油苷的生成,水杨酸和乙烯则能轻度诱导4-甲氧吲哚-3-甲基芥子油苷的生成。植物防卫信号转导途径相互作用以精细调节不同种类吲哚类芥子油苷的生成。     

NaCl胁迫对盐芥质膜和液泡膜ATPase活性的影响

以盐生植物盐芥和中生植物拟南芥幼苗为材料,研究了盐胁迫对它们叶片和根质膜、液泡膜H+-ATPase、Ca2+-ATPases和K+-ATPase活性以及H+-ATPase、Na+/H+ 逆向转运蛋白表达的影响.结果显示:在NaCl胁迫下,盐芥叶片和根质膜的H+-ATPase活性分别比对照显著升高41%～212%和35%～53%,液泡膜的H+-ATPase分别显著升高281%～373%和4%～38%,而拟南芥却比相应对照都显著降低;相同盐浓度胁迫下,盐芥叶片的H+-ATPase活性比根部高4～8倍,盐芥根也远高于拟南芥.在NaCl胁迫下,盐芥叶片和根的液泡膜H+-ATPase蛋白质β亚基含量变化与其酶活性变化趋势一致,质膜Na+/H+ 逆向转运蛋白的表达量与Na+含量变化趋势一致.盐胁迫下盐芥根中Ca2+-ATPases和K+-ATPase活性的增加与根中Ca2+和K+含量呈显著正相关.研究发现,在盐胁迫条件下,盐芥能有效增强H+-ATPase蛋白和Na+/H+逆向转运蛋白表达,显著提高其根系与叶片质膜和液泡膜的H+-ATPase、Ca2+-ATPase和K+-ATPase活性,维持细胞质中较高的Ca2+和K+水平,从而缓解盐胁迫的伤害,增强耐盐性.     

盐芥响应盐胁迫的分子机制研究进展

盐生植物盐芥是拟南芥的近缘物种,具有极强的耐盐能力,是很有研究前景的新兴耐盐模式植物.该文主要从离子平衡(Na+的吸收、外排、区隔化)、渗透平衡和过氧化物清除3个方面对近年来国内外有关盐芥耐盐分子机制的研究进展进行综述,以阐述盐芥植物对于盐胁迫反应的生理及分子机制.     

盐胁迫对盐芥生长及硝酸还原酶活性的影响

盐胁迫处理导致盐芥植株鲜重、干重、含水量、肉质化程度和根冠比都下降;根中有机物含量上升,而无机物含量下降,叶的变化与根的相反;渗透调节能力、Na 含量和根系活力上升;硝酸还原酶活性显著增加;超氧阴离子(O2-)含量先降低后升高.表面扫描电镜图像显示:盐芥叶片表面没有盐腺或盐囊泡,所以它不是泌盐盐生植物.盐芥生长状况、Na 含量和Na X-ray微区分析结果表明:盐芥也不是拒盐盐生植物,而很可能是稀盐盐生植物.     

植物中的吲哚族芥子油苷与生长素代谢途径的关系

文章介绍了植物中的吲哚族芥子油苷代谢与生长素合成途径相互关系的研究进展。     

Efficiency of biochemical protection against toxic effects of accumulated salt differentiates Thellungiella halophila from Arabidopsis thaliana

Thellungiella halophila and Arabidopsis thaliana were irrigated with medium containing NaCl at various concentrations. The salt treatment resulted in a restriction of rosette biomass deposition in both species. In A. thaliana leaves, this inhibition was stronger than for T. halophila and was associated with strong inhibition of both leaf initiation and leaf expansion. At highest medium salinity, A. thaliana accumulated Na(+) and Cl(-) at higher levels than T. halophila, but similar leaf dehydration was observed in the two species. Proline accumulation, which increased with NaCl concentration, did not differentiate the two species. The magnitude of the electrolyte leakage and the level of lipid peroxidation (assessed through hydroxy fatty acid content) were modest in T. halophila and quite marked in A. thaliana. The detrimental effects of the salt on photosynthetic activity and stomatal conductance of A. thaliana leaves were much more important than in T. halophila leaves. The abundance of the CDSP32 thioredoxin, a critical component of the defence system against oxidative damage and lipid peroxidation, was found to be higher in T. halophila than in A. thaliana under control conditions and salt treatment. These results suggest that the rosette leaves of T. halophila exhibit more efficient protective mechanisms against Na(+) metabolic toxicity than those of A. thaliana.     

Effects of NaCl on the growth, ion accumulation and photosynthetic parameters of Thellungiella halophila

Thellungiella halophila seedlings grown on a solid substrate for 25 days on standard medium were challenged with NaCl. Growth, tissue hydration, ion accumulation, photosynthesis, lipid peroxidation and antioxidant enzymatic activities were studied on rosette leaves. Three accessions of Arabidopsis thaliana were cultivated under the same conditions. During the first two weeks of salt treatment, the growth of T. halophila leaves was restricted by NaCl. No significant difference appeared between T. halophila and A. thaliana concerning biomass deposition, or hydric and ionic parameters. However, all A. thaliana plants displayed foliar damage, and died during the third week of salt (50mM NaCl) treatment. Almost all (94%) T. halophila plants remained alive, but did not display any sign of altered physiological condition. Tissue hydration, chlorophyll content, stomatal conductance, photosynthetic quantum yield, and photosynthetic rate were very similar to those of control plants. Lipid peroxidation, estimated from thermoluminescence, was very low and insensitive to salt treatment. Only slight changes occurred in antioxidant enzymatic activities (SOD, several peroxidases, and catalase). From the absence of physiological disorder symptoms, we infer that salt was efficiently compartmentalized in leaf vacuoles. In salt-treated A. thaliana, the photosynthetic quantum yield was diminished, and lipid peroxidation was augmented. These observations reinforce the conclusion that T. halophila could accumulate salt in its leaves without damage, in contrast to A. thaliana.     

基于核磁共振波谱的盐芥盐胁迫代谢组学分析

以甲醇/水(1∶1)作为溶剂,利用高分辨核磁共振氢谱分析了盐生模式植物盐芥(Thellungiella salsuginea)代谢组对盐胁迫的响应。根据1H核磁共振(NMR)波谱,在盐芥莲座叶中准确鉴定出23种代谢产物,包括11种氨基酸、4种糖类、6种有机酸和2种其他代谢产物。主成分分析表明,150、300 mmol/L NaCl处理盐芥的代谢组与对照均有显著差异(P<0.05),两种浓度的NaCl处理对盐芥代谢组的影响也不相同。盐胁迫处理以后,盐芥23种代谢产物含量均发生显著变化,除天冬氨酸、延胡索酸受盐胁迫诱导含量下降以外,其余代谢物含量均不同程度升高。这些代谢物主要参与了糖类代谢途径、氨基酸合成途径、三羧酸循环和甜菜碱合成途径,这些代谢途径在盐芥响应盐胁迫过程中有重要作用。     

盐胁迫下盐桦生理响应的变化分析

对组织培养获得的盐桦（Belula halophila）苗在盐胁迫下的生理指标和解剖结构进行了分析,结果显示,随着盐浓度的增加,植物叶片相对含水量逐渐降低;脯氨酸（Pro）含量逐渐增加;叶片丙二醛（MDA）含量和过氧化氢酶（CAT）活性大小存在相关性,在50～200mmol／L盐胁迫下,植物的CAT活性是递增的,200mmol／LNaCl处理时达到最高,同时叶片MDA含量在50～200mmol／L盐处理时变化不明显;CAT活性在300mmol／LNaCl处理时突然降低,此时叶片MDA含量大;植物叶片和根的离子含量测定表明,在盐胁迫下K^＋／Na^＋比值逐渐降低,叶片中K^＋含量始终高于Na^＋含量;石蜡切片和扫描电镜发现盐桦茎、叶中有晶体状物质存在,通过X-ray分析表明这种晶体含有C,O,Ca元素,相关的细胞成分化学实验进一步确定其结晶体的成分。     

Low unidirectional sodium influx into root cells restricts net sodium accumulation in Thellungiella halophila, a salt-tolerant relative of Arabidopsis thaliana

Thellungiella halophila is a useful model species for research into plant salt tolerance. It is closely related to Arabidopsis thaliana, but shows considerably higher salt tolerance. Comparative analysis of ion homeostasis in the two species allows the identification of ion transport pathways that are critical for salt tolerance and provides the basis for future studies into their molecular features. Previous studies indicated that salt tolerance in T. halophila is accompanied by low accumulation of Na in the leaves. Kinetic analysis of net ion uptake over three days confirmed lower Na uptake and K loss in T. halophila compared with A. thaliana. Differential net Na uptake rates were still apparent after 6 weeks of salt treatment. To assess the contribution of unidirectional Na fluxes to net Na uptake, kinetic studies of (22)Na fluxes were carried out in both species. The results show that unidirectional root Na influx is significantly lower in salt-grown T. halophila plants than in A. thaliana exposed to the same level of salinity (100 mM). Quantitative comparison of unidirectional influx and net Na accumulation suggests that both species operate efficient Na efflux, which partly compensates for Na influx. Kinetic analysis of (22)Na efflux indicated higher root Na efflux in A. thaliana than in T. halophila. Thus A. thaliana appears to spend more energy on Na export while nevertheless accumulating more Na than T. halophila. It is proposed that limitation of Na influx is the main mechanism by which T. halophila secures low net Na accumulation in saline conditions. This strategy provides the basis for a positive balance between growth and net Na uptake rates, which is essential for survival in high salt.     

NaCl和Na2CO3胁迫对桑树幼苗生长和光合特性的影响

以1年生“青龙桑”幼苗为试验材料,研究了中性盐(NaCl)和碱性盐(Na2CO3)胁迫下桑树幼苗的生长和叶片光合特性.结果表明:盐胁迫明显降低了桑树幼苗的株高、叶片数、生物量和叶片的光合能力.随着Na+浓度的增加,桑树叶片的气孔导度、蒸腾速率、净光合速率、实际光化学效率、电子传递速率和光化学猝灭系数明显降低,过剩光能以非光化学猝灭形式耗散的比例增加,桑树叶片的光能转化效率和光合能力下降.在Na+浓度＜150 mmol·L-1时,桑树幼苗的光合能力和生长受到的抑制较小,通过增加根冠比进一步适应盐胁迫,但这种保护机制随着盐浓度的增加逐渐降低.在Na2CO3胁迫下,＞50 mmol·L-1 Na+浓度对桑树的生长和光合能力表现出较强的抑制作用,并随Na+浓度的增加,抑制程度加大.在NaCl＜ 150mmol·L-1时,桑树的光合能力主要依赖植株形态和光合代谢双重途径适应中性盐逆境,而在NaC1浓度＞150 mmol·L-1和碱性盐胁迫下,其主要依赖光合代谢来适应逆境.