外源GSH对盐胁迫下水稻叶绿体活性氧清除系统的影响

研究了外源GSH对盐胁迫下耐盐性不同的水稻品种Pokkali(耐盐)和Peta(盐敏感)叶绿体中抗氧化酶活性和抗氧化剂含量的影响.结果表明:盐胁迫下,外源GSH可以提高水稻叶绿体中活性氧清除系统中SOD、APX、GR的活性以及AsA、GSH的含量,降低叶绿体中H2O2和MDA的含量,从而降低了叶绿体膜脂过氧化的水平,缓解盐胁迫对叶绿体膜的伤害.外源GSH对盐胁迫下盐敏感品种Peta叶绿体中上述指标增加或减少的幅度大于耐盐品种Pokkali.     

核黄素参与水稻非生物胁迫响应的分析

为探究核黄素在水稻非生物胁迫响应中的作用,以粳稻Kitaake和籼稻T98B为试验材料,考察了核黄素对2种材料的盐、高温、渗透、碱和氧化胁迫响应的影响,重点测定了盐和高温胁迫下水稻体内核黄素合成基因的表达和相关生理指标。结果表明,(1)施加外源核黄素有效提高了2种水稻材料的盐和高温胁迫耐受性,降低了渗透胁迫耐受性,而其氧化和碱胁迫耐受性不受影响。(2)逆境胁迫均不同程度地促进了核黄素在2种水稻材料中的积累,尤其在盐和高温胁迫下促进效果最明显。(3)盐和高温胁迫均诱导了核黄素合成酶基因的表达,促进了核黄素的生物合成,改善了水稻的胁迫耐受性。研究表明,非生物逆境胁迫能促进核黄素在水稻体内的合成和积累,外源核黄素也能明显提高水稻对盐和高温胁迫的耐受性,但却降低了其对渗透胁迫的耐受性。     

外源一氧化氮对盐胁迫下黄瓜幼苗生长和渗透调节物质含量的影响

采用水培法,研究了外源一氧化氮(NO)对黄瓜幼苗生长和渗透调节物质含量的影响。结果表明:正常生长条件下添加外源NO能促进黄瓜幼苗生长,而添加NO信号传递途径关键酶——鸟苷酸环化酶抑制剂亚甲基蓝(MB-1)显著抑制了黄瓜幼苗的生长;盐胁迫条件下,添加外源NO明显缓解了盐胁迫对黄瓜幼苗生长的抑制,与单独盐处理比较,株高、茎粗、鲜质量、干质量显著增加,渗透调节物质如可溶性糖、可溶性蛋白和脯氨酸含量明显提高,而MB-1能够不同程度地消除NO的这些调节作用;NO对盐胁迫下黄瓜幼苗生长影响大于正常生长条件下黄瓜幼苗,NO的作用可能是通过鸟苷酸环化酶介导的。     

外源甜菜碱提高小麦幼苗抗盐性的研究

以小麦品系山农215953(SN215953)为材料,采用水培的方法,于幼苗期(两叶一心)根灌15mmol·L-1甜菜碱,研究了外源甜菜碱对盐胁迫下小麦幼苗水分状况、脯氨酸和可溶性糖含量及抗氧化酶活性的影响。结果表明:(1)外源甜菜碱可缓解盐渍造成的小麦幼苗叶片的水分损失,改善小麦幼苗的水分状况,并发现甜菜碱的这种作用主要是通过促进脯氨酸和可溶性糖的积累进而提高小麦叶片的渗透调节能力来实现。(2)外源甜菜碱可以维持盐胁迫下小麦幼苗叶片的抗氧化酶(SOD、APX、POD)活性,缓解盐渍造成的盐胁迫伤害,对盐胁迫下小麦幼苗生物膜的稳定性和完整性起到保护作用。     

外源亚精胺对盐胁迫下黄瓜幼苗体内抗氧化酶活性的影响

以不同耐盐性黄瓜品种“长春密刺”和“津春2号”为材料,采用营养液栽培,研究了外源亚精胺(Spd)对NaCl胁迫下黄瓜幼苗叶片与根系中超氧阴离子(O2-.)产生速率、超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性的影响。结果表明,外源Spd对未经盐胁迫处理(对照)黄瓜幼苗体内O2-.产生速率、SOD、CAT和POD活性均无显著性影响;盐胁迫处理提高了O2-.产生速率,SOD、POD和CAT活性都有不同程度的升高;外源Spd处理进一步提高了盐胁迫下SOD、POD和CAT活性,减缓了O2-.产生速率。与耐盐型“长春密刺”品种相比,盐胁迫对盐敏感型“津春2号”影响较大,外源Spd对盐敏感型黄瓜品种盐胁迫伤害的缓解作用较大。表明盐胁迫下外源Spd可缓解盐胁迫对膜的伤害,从而提高黄瓜幼苗的耐盐性。     

He-Ne激光对盐胁迫下水稻幼苗抗氧化活性的影响

为减轻盐胁迫对植物造成的伤害,本研究采用He-Ne激光对盐胁迫下的水稻进行辐照处理,选用水稻9311作为对照、耐盐海稻86作为研究对象,以0.5%的氯化钠进行盐胁迫,He-Ne激光(辐照计量5 m W·mm-2,波长632.8 nm)进行照射。设置了对照组(CK),盐胁迫组、盐胁迫和激光复合处理组(分别为L、BL组),进行了水稻抗氧化活性方面的研究。结果表明:与对照组(CK)比较,He-Ne激光对水稻的盐胁迫有一定的缓解作用,其中对水稻9311的作用最明显,表现为激光处理提高了水稻幼苗中过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)的活性和减缓了丙二醛(MDA)含量的增速;同时也说明新选育的海稻86耐盐性高于水稻9311。因此,一定剂量的He-Ne激光可以提高了水稻的耐盐性,这为抗盐胁迫及耐盐植物的育种提供了途径和理论依据。     

盐胁迫下外源NO对苜蓿幼苗生长及氮代谢的影响

为探寻增强苜蓿耐盐能力的调控途径,以甘农4号苜蓿品种为材料,采用NO供体硝普钠、NO清除剂c-PTIO及硝普钠类似物亚铁氰化钠处理苜蓿幼苗,研究盐胁迫下外源NO对苜蓿幼苗生长、光合特征、氮同化酶活性和氮代谢物含量的影响.结果表明: 外源NO能明显缓解盐胁迫对苜蓿幼苗生长及光合作用的抑制,单株干质量、叶绿素含量、净光合速率、蒸腾速率和可溶性蛋白含量增加;外源NO能增强硝酸还原酶、谷氨酰胺合成酶和谷氨酸合酶活性,抑制蛋白水解酶和谷氨酸脱氢酶活性, 降低叶片中游离氨基酸含量,提高硝态氮含量,加快铵的同化.NO供体SNP的类似物亚铁氰化钠对盐胁迫下苜蓿幼苗生长及氮代谢无调控作用;施用NO清除剂c-PTIO加剧了盐胁迫对苜蓿幼苗生长和氮代谢的抑制,添加外源NO能缓解c-PTIO的抑制效应.盐胁迫下,外源NO和内源NO均参与了苜蓿幼苗氮代谢的调控.     

外源褪黑素对盐胁迫下银杏幼苗渗透调节和抗氧化能力的影响

以4年生银杏幼苗为材料,进行不同浓度盐胁迫(50、100、200 mmol·L^-1)处理,叶片喷施和土壤浇灌外源褪黑素溶液(0、0.02、0.1、0.5 mmol·L^-1),研究外源褪黑素对盐胁迫下银杏幼苗渗透调节和抗氧化能力的影响。结果表明：盐胁迫显著抑制银杏幼苗渗透调节和抗氧化能力,而在盐胁迫下施用适宜浓度(0.02、0.1 mmol·L^-1)的外源褪黑素能够促进植株生长,降低电解质外渗率,减少黄酮和丙二醛含量,促进叶片中过氧化物酶、超氧化物歧化酶(SOD)活性的提高,但高浓度(0.5 mmol·L^-1)外源褪黑素会进一步加剧氧化胁迫和渗透胁迫。0.02和0.1 mmol·L^-1外源褪黑素处理缓解了盐胁迫下银杏幼苗的渗透胁迫和氧化胁迫,且0.02 mmol·L^-1外源褪黑素处理对盐胁迫缓解效果最佳。地径、枝条宽度、枝条长度、电解质外渗率、SOD活性和黄酮含量可作为快速鉴定银杏受盐胁迫程度的关键指标。     

外源壳聚糖对NaCl胁迫下菜用大豆光合作用及荧光特性的影响

采用蛭石栽培,以耐盐性不同的2个菜用大豆[Glycine max(L.)Merr.]品种为试材,研究外源壳聚糖对NaCl胁迫下幼苗叶片光合及叶绿素荧光参数的影响,探讨外源壳聚糖调控菜用大豆光合作用的生理机制。结果显示:(1)外源壳聚糖通过诱导非气孔因素显著缓解了盐敏感品种‘理想高产95-1’(LX)在胁迫第6、9、12天时净光合速率(Pn)的下降,但胁迫第15天该作用消失;通过同时诱导气孔因素和非气孔因素缓解了耐盐品种‘绿领特早’(LL)在胁迫第3、6天时Pn的下降,其后Pn下降的缓解则主要通过诱导非气孔因素实现,且LL的Pn较盐处理的增幅均高于同期的LX。(2)外源壳聚糖阻止了LX在盐胁迫第12天、LL在胁迫第15天时非光化学猝灭系数(NPQ)的下降;外源壳聚糖显著缓解了LL在盐胁迫第15天时光化学猝灭系数(qP)、实际光化学效率(ФPSⅡ)的下降。(3)无盐条件下,外源壳聚糖在处理早期通过诱导气孔导度(Gs)、qP及ФPSⅡ等气孔和非气孔因素显著提高了两品种菜用大豆的Pn,但中、后期该作用消失。研究表明,菜用大豆具有潜在的抗逆性,外源壳聚糖在NaCl胁迫下对菜用大豆的作用与无盐条件下不同;壳聚糖只有在菜用大豆受到盐胁迫伤害时才可诱导其潜在的抗盐性,但其诱导途径、诱导时效、诱导效果因品种耐盐性不同而异;耐盐品种LL具有较强、持久且多元的潜在抗逆能力,这可能是其经壳聚糖诱导后能维持相对较高Pn的重要原因之一。     

外源蔗糖和Ca2+对荞麦幼苗耐盐性的影响

以盐敏感荞麦品种‘TQ-0808’为实验材料,在100mmol·L-1NaCl胁迫下研究添加不同浓度蔗糖和Ca2+处理对荞麦幼苗耐盐性的影响。不同浓度的外源蔗糖和Ca2+处理均能明显降低盐胁迫下荞麦叶片的质膜透性和丙二醛(MDA)含量,明显增加荞麦叶片的超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)活性及净光合速率,且外源Ca2+处理的增加效果明显好于外源蔗糖处理。说明外源蔗糖和Ca2+处理能明显改善盐胁迫下荞麦幼苗的耐盐性,对盐胁迫具有较好的缓解作用,外源蔗糖和Ca2+处理的最适浓度分别为6mmol·L-1和20mmol·L-1。     

Protective role of exogenous polyamines on salinity-stressed rice (Oryza sativa) plants

Salt-tolerant Pokkali rice plants accumulate higher polyamines (PAs) such as spermidine (Spd) and spermine (Spm) in response to salinity stress, while the sensitive cultivar M -1–48 is unable to maintain high titres of these PAs under similar conditions. The effects of the triamine Spd and the tetramine Spm on physiological and biochemical changes in 12-day-old rice seedlings were investigated during salinity stress to determine whether they could protect the sensitive plants from stress effects. At physiological concentrations Spd and Spm significantly prevented the leakage of electrolytes and amino acids from roots and shoots induced by salinity stress. To different degrees they also prevented chlorophyll loss, inhibition of photochemical reactions of photosynthesis as well as downregulation of chloroplast-encoded genes like psbA , psbB , psbE and rbcL , indicating a positive correlation between salt tolerance and accumulation of higher PAs in rice. The inhibitory effect of salinity stress and its reversal by exogenous PAs were more pronounced in the salt-sensitive M -1–48 plants than in the tolerant Pokkali plants.     

Identification and characterization of salt responsive miRNA-SSR markers in rice (Oryza sativa)

Salinity is an important abiotic stress that affects agricultural production and productivity. It is a complex trait that is regulated by different molecular mechanisms. miRNAs are non-coding RNAs which are highly conserved and regulate gene expression. Simple sequence repeats (SSRs) are robust molecular markers for studying genetic diversity. Although several SSR markers are available now, challenge remains to identify the trait-specific SSRs which can be used for marker assisted breeding. In order to understand the genetic diversity of salt responsive-miRNA genes in rice, SSR markers were mined from 130 members of salt-responsive miRNA genes of rice and validated among the contrasting panels of tolerant as well as susceptible rice genotypes, each with 12 genotypes. Although 12 miR-SSRs were found to be polymorphic, only miR172b-SSR was able to differentiate the tolerant and susceptible genotypes in 2 different groups. It had also been found that miRNA genes were more diverse in susceptible genotypes than the tolerant one (as indicated by polymorphic index content) which might interfere to form the stem-loop structure of premature miRNA and their subsequent synthesis in susceptible genotypes. Thus, we concluded that length variations of the repeats in salt responsive miRNA genes may be responsible for a possible sensitivity to salinity adaptation. This is the first report of characterization of trait specific miRNA derived SSRs in plants.     

Germination profiling of lentil genotypes subjected to salinity stress

• Salinity is one of the most severe environmental stresses, negatively affecting productivity of salt‐sensitive crop species. Given that germination is the most critical phase in the plant life cycle, the present study aimed to determine seed germination potential and associated traits under salt stress conditions as a simple approach to identify salt‐tolerant lentil genotypes.
• The genetic material consisted of six lentil genotypes whose adaptation to various agroclimatic conditions is not well elucidated. Salinity stress was applied by addition of NaCl at three different levels of stress, while non‐stressed plants were included as controls. Evaluation of tolerance was performed on the basis of germination percentage, seed water absorbance, root and shoot length, seedling water content, seedling vigour index and number of seedlings with an abnormal phenotype.
• Overall, our findings revealed that salinity stress substantially affects all traits associated with germination and early seedling growth, with the effect of salinity being dependent on the level of stress applied. It is noteworthy, however, that genotypes responded differently to the varying salinity levels. In this context, Samos proved the most salt‐tolerant genotype, indicating its possible use for cultivation under stress conditions.
• In conclusion, the determination of seed germination and early growth potential may be exploited as an efficient strategy to reveal genetic variation in lentil germplasm of unknown tolerance to salinity stress. This approach allows selection of desirable genotypes at early growth stages, thus enabling more efficient application of various breeding methods to achieve stress‐tolerant lentil genotypes.

     

ABA Inducible Rice Protein Phosphatase 2C Confers ABA Insensitivity and Abiotic Stress Tolerance in Arabidopsis

Arabidopsis PP2C belonging to group A have been extensively worked out and known to negatively regulate ABA signaling. However, rice (Oryza sativa) orthologs of Arabidopsis group A PP2C are scarcely characterized functionally. We have identified a group A PP2C from rice (OsPP108), which is highly inducible under ABA, salt and drought stresses and localized predominantly in the nucleus. Genetic analysis revealed that Arabidopsis plants overexpressing OsPP108 are highly insensitive to ABA and tolerant to high salt and mannitol stresses during seed germination, root growth and overall seedling growth. At adult stage, OsPP108 overexpression leads to high tolerance to salt, mannitol and drought stresses with far better physiological parameters such as water loss, fresh weight, chlorophyll content and photosynthetic potential (Fv/Fm) in transgenic Arabidopsis plants. Expression profile of various stress marker genes in OsPP108 overexpressing plants revealed interplay of ABA dependent and independent pathway for abiotic stress tolerance. Overall, this study has identified a potential rice group A PP2C, which regulates ABA signaling negatively and abiotic stress signaling positively. Transgenic rice plants overexpressing this gene might provide an answer to the problem of low crop yield and productivity during adverse environmental conditions.     

Overexpression of Rice Sphingosine-1-Phoshpate Lyase Gene OsSPL1 in Transgenic Tobacco Reduces Salt and Oxidative Stress Tolerance

Sphingolipids, including sphingosine-1-phosphate (S1P), have been shown to function as signaling mediators to regulate diverse aspects of plant growth, development, and stress response. In this study, we performed functional analysis of a rice (Oryza sativa) S1P lyase gene OsSPL1 in transgenic tobacco plants and explored its possible involvement in abiotic stress response. Overexpression of OsSPL1 in transgenic tobacco resulted in enhanced sensitivity to exogenous abscisic acid (ABA), and decreased tolerance to salt and oxidative stress, when compared with the wild type. Furthermore, the expression levels of some selected stress-related genes in OsSPL1-overexpressing plants were reduced after application of salt or oxidative stress, indicating that the altered responsiveness of stress-related genes may be responsible for the reduced tolerance in OsSPL1-overexpressing tobacco plants under salt and oxidative stress. Our results suggest that rice OsSPL1 plays an important role in abiotic stress responses.     

Overexpression of <Emphasis Type="Italic">OsiSAP8</Emphasis>, a member of stress associated protein (SAP) gene family of rice confers tolerance to salt,drought and cold stress in transgenic tobacco and rice

We describe here the isolation and characterization of OsiSAP8, a member of stress Associated protein (SAP) gene family from rice characterized by the presence of A20 and AN1 type Zinc finger domains. OsiSAP8 is a multiple stress inducible gene, induced by various stresses, namely heat, cold, salt, desiccation, submergence, wounding, heavy metals as well as stress hormone Abscisic acid. OsiSAP8 protein fused to GFP was localized towards the periphery of the cells in the epidermal cells of infiltrated Nicotiana benthamiana leaves. Yeast two hybrid analysis revealed that A20 and AN1 type zinc-finger domains of OsiSAP8 interact with each other. Overexpression of the gene in both transgenic tobacco and rice conferred tolerance to salt, drought and cold stress at seed germination/seedling stage as reflected by percentage of germination and gain in fresh weight after stress recovery. Transgenic rice plants were tolerant to salt and drought during anthesis stage without any yield penalty as compared to unstressed transgenic plants. OsiSAP8 is deposited in the Genbank with the Accession number AY345599.