Synthetic gibberellin synergists in elongation of shoot growth ofOryza sativa L.

Previous studies showed that 2-ethyl-3-methoxycarbonyl-1-(p-tolylcarbamoyl) isourea acts as a potent GA₃-synergist in stimulating shoot growth of rice seedlings. Studies with several structurally related compounds show that the alkoxycarbonylcarbamoyl-isourea or -isothiourea skeleton is required for biological activity. Any chemical deletion from this skeleton causes complete loss of activity. From present and previous data it seems that alkoxycarbonylcarbamoyl-isourea or -isothiourea is converted by intramolecular cyclization in the rice seedlings into the corresponding triazinone that serves as the active form.     

Gibberellin biosynthetic pathway and the physiologically active gibberellin in the shoot ofCucumis sativus L.

[²H₂]Gibberellin A₂₄ (GA₂₄) and [²H₄]-GA₉ were applied to the apices of normal-type cucumber (Cucumis sativus L. cv. Yomaki) seedlings treated with uniconazole, an inhibitor of GA biosynthesis. The metabolites from these feeds were identified by full-scan gas chromatography-mass spectrometry (GC-MS) to confirm the conversions of [²H₂]GA₂₄ to [²H₂]GA₉ and of [²H₄]GA₉ to [²H₄]GA₄. The results show that GA₄ is biosynthesized from GA₂₄ via GA₉. In a cucumber hypocotyl elongation bioassay using cv. Yomaki, prohexadione (DOCHC), an inhibitor of 2-oxoglutaratedependent dioxygenase, inhibited the hypocotyl elongation caused by application of GA₉, while DOCHC enhanced the elongation caused by application of GA₄. These results indicate that GA₄ is a physiologically active GA and that the activity of GA₉ is due to its conversion to GA₄ in cucumber shoots.     

The transfer RNA genes in Oryza sativa L. ssp. indica

The availability of the draft genome sequence of Oryza sativa L. ssp. indica has made it possible to study the rice tRNA genes. A total of 596 tRNA genes, including 3 selenocysteine tRNA genes and one suppressor tRNA gene are identified in 127551 rice contigs. There are 45 species of tRNA genes and the revised wobble hypothesis proposed by Guthrie and Abelson is perfectly obeyed. The relationship between codon usage and the number of corresponding tRNA genes is discussed. Redundancy may exist in the present list of tRNA genes and novel ones may be found in the future. A set of 33 tRNA genes is discovered in the complete chloroplast genome of Oryza sativa L. ssp. indica. These tRNA genes are identical to those in ssp. japonica identified by us independently from the origional annotation.     

Elicitation studies in cell suspension cultures of Cannabis sativa L.

Cannabis sativa L. plants produce a diverse array of secondary metabolites. Cannabis cell cultures were treated with biotic and abiotic elicitors to evaluate their effect on secondary metabolism. Metabolic profiles analysed by ¹H NMR spectroscopy and principal component analysis (PCA) showed variations in some of the metabolite pools. However, no cannabinoids were found in either control or elicited cannabis cell cultures. Tetrahydrocannabinolic acid (THCA) synthase gene expression was monitored during a time course. Results suggest that other components in the signaling pathway can be controlling the cannabinoid pathway.     

Evaluation of cadmium genotoxicity in Lactuca sativa L. using nuclear microsatellites

Cadmium (Cd) is a non-essential element and is a widespread environmental pollutant. Exposure to cadmium can result in cytotoxic, carcinogenic and mutagenic effects. Mutagenesis is indicative of genetic instability and can be assayed using microsatellites. Microsatellites or simple sequence repeats (SSRs) are composed of tandem repeats of short sequence motifs (1–6 bp) that are polymorphic, mainly in the number of tandem repeated units. Therefore, chromosomic mutations like inversion, deletion or translocation and point mutations can be detected by this type of molecular marker. In this study we have evaluated the mutagenic/genotoxic effects of cadmium in lettuce (Lactuca sativa L.). Five-week-old lettuce plants grown in a modified Hoagland's medium were exposed for a further 14 days to a medium containing 100 μM Cd(NO₃)₂. Genomic DNA was extracted from lettuce leaves and roots, harvested at days 0, 1, 3, 7 and 14, and nine SSRs were tested, amplified and analysed to evaluate microsatellite instability (MSI). Mutagenic effects of cadmium on microsatellite DNA loci were assessed and no MSI was observed in the used markers.     

紫花苜蓿逆境响应转录因子MsNAC3基因克隆及表达分析

该研究利用RT-PCR和RACE技术,克隆了1个紫花苜蓿NAC类转录因子新基因,命名为MsNAC3(GenBank登录号为KC491186)。多重比对发现,MsNAC3蛋白与蒺藜苜蓿MtNAC和鹰嘴豆CarNAC5蛋白的同源性较高,其N端含有典型的NAC保守结构域,C端高度变异;进化树聚类分析表明,MsNAC3与紫花苜蓿MsNAC2和油菜BnNAC3亲缘关系较近,属于NAC蛋白的ATAF亚家族。洋葱亚细胞定位分析表明,MsNAC3定位于细胞核。转录水平表达分析表明,MsNAC3受盐、干旱、ABA和冷害胁迫诱导而显著升高,并且MsNAC3在根中的表达量要明显高于叶中。研究表明,MsNAC3基因可能作为一个正向调控因子在逆境胁迫信号转导过程中发挥重要作用。     

紫花苜蓿赤霉素受体基因的克隆及表达分析

赤霉素受体(GID)是赤霉素信号转导途径的重要成员,直接影响着赤霉素对植物体效应的发挥。该研究利用同源克隆的方法,首次从紫花苜蓿中克隆得到1个赤霉素受体基因,命名为MsGID1b。序列分析发现,MsGID1b基因开放阅读框长度为1 053bp,编码350个氨基酸,推测其蛋白质分子量为39.839kD,是一个无信号肽和跨膜结构的亲水性蛋白。序列比对结果表明,MsGID1b基因与蒺藜苜蓿MtGID1b基因的核苷酸序列相似性为98%,氨基酸序列相似性为99%,且具有HSL家族典型的HGG和GXSXG保守结构域及GA、DELLA蛋白结合位点。荧光定量PCR分析表明,MsGID1b基因在紫花苜蓿各组织中的表达丰度依次为:根盛花初花茎叶荚果;经GA3、ABA、NaCl、PEG和黑暗诱导后该基因表达上调,尤其是在GA3诱导下,MsGID1b基因的表达量一直维持在较高水平,表明MsGID1b基因可能参与紫花苜蓿的抗逆调控。     

紫花苜蓿UV-B光受体基因MsUVR8的克隆及功能研究北大核心CSCD

该研究采用RACE扩增技术克隆了一个紫花苜蓿UV-B光受体基因(MsUVR8),在生物信息学分析基础上,采用农杆菌介导法获得了该基因过表达愈伤组织,并对UV-B辐射处理后MsUVR8过表达愈伤组织及其野生型中的类黄酮、黄酮醇、花青素、过氧化氢(H_(2)O_(2))、超氧阴离子(O_(2)^(-·))含量以及UV-B信号通路相关基因的表达进行检测分析,以探讨MsUVR8基因的生物学功能,为揭示植物响应UV-B胁迫的分子机制奠定理论基础。结果表明:(1)成功克隆获得紫花苜蓿MsUVR8基因CDS序列834 bp,且MsUVR8与蒺藜苜蓿MtUVR8基因序列相似度高达95%以上;MsUVR8蛋白形成了不完整的β-折叠结构,系统发育分析显示其与鹰嘴豆属于同一分支。(2)对MsUVR8过表达系检测发现,紫花苜蓿MsUVR8过表达愈伤组织(UVR8-OE)中类黄酮含量较野生型愈伤组织(WT)明显升高,而且经UV-B辐射后的UVR8-OE类黄酮物质含量较WT进一步显著升高。(3)DPBA荧光标记实验发现,UV-B辐射大大促进了细胞中黄酮醇的合成,且UV-B辐射后的UVR8-OE中黄酮醇含量最高。(4)DAB和NBT染色显示,UV-B处理后WT中活性氧(H_(2)O_(2)和O_(2)^(-·))的积累增加,而在UV-B辐射处理与未处理的UVR8-OE中H_(2)O_(2)和O_(2)^(-·)的积累无明显差异,表明MsUVR8可增强植物组织细胞的抗氧化性能,并可降低UV-B胁迫引起的氧化损伤。(5)UV-B辐照后,WT中PAL、CHS和FLS表达被激活而显著提高,UVR8-OE中的4种基因表达均达到最大,且较其他3个处理组均显著增强。研究认为,紫花苜蓿MsUVR8被UV-B激活后,促进了类黄酮合成相关基因的表达,并激活了类黄酮合成关键酶的活性,从而提高了类黄酮物质的合成效率,增强了UV-B胁迫条件下植物愈伤组织的抗氧化能力。     

苹果MAX1基因的克隆和表达及启动子分析

MAX1(MORE AXILLARY GROWTH1)是独脚金内酯(Strigolactones,SLs)合成途径中的关键基因,为了研究MAX1在苹果分枝调控中的功能,以苹果‘长富2号’(Malus domestica‘Nagafu 2’)腋芽为材料,采用PCR方法,克隆MdMAX1基因,进行生物信息学和表达水平分析;采用瞬时表达转化烟草,进行GUS染色,分析MdMAX1启动子活性。结果表明:(1)成功克隆得到苹果MAX1,其开放阅读框(ORF)1620 bp,编码539个氨基酸;系统进化和基序分析表明,MdMAX1和已知的A1型MAX1相似。(2)qRT-PCR分析表明,MAX1基因在‘长富2号’嫁接苗茎中高表达,并在腋芽本身有表达;RNA-seq分析表明,细胞分裂素(6-BA)处理苹果腋芽96 h后MAX1基因的表达水平显著降低。(3)成功克隆获得‘长富2号’MAX1启动子序列片段(1500 bp),顺式作用元件预测显示MdMAX1启动子序列中存在光响应元件,GUS活性分析表明光照处理能够减弱MAX1启动子的活性。该研究为进一步研究苹果MAX1参与SLs合成、调控苹果分枝的功能奠定了基础。     

水稻MITEs类转座子mPing研究进展

Miniature Ping(mPing)是小型反向重复转座子(Miniature Inverted-Repeat Transposable Elements,MITEs)类转座子Tourist-like超家族重要成员,是水稻基因组内检测到的第一个活跃的MITEs,是MITEs大家族中少数低拷贝且可以在自然状态下维持转座活性的成员之一,因此,mPing是转座子相关领域研究的良好素材。该文综合阐述了近年来国内外有关mPing的结构、转座酶供体、激活特性以及对基因组的影响等方面的研究进展,为进一步深入探究MITEs的转座机制以及mPing转座子的开发利用提供资料。     

Gibberellin biosynthetic pathway and the physiologically active gibberellin in the shoot ofCucumis sativus L.

[²H₂]Gibberellin A₂₄ (GA₂₄) and [²H₄]-GA₉ were applied to the apices of normal-type cucumber (Cucumis sativus L. cv. Yomaki) seedlings treated with uniconazole, an inhibitor of GA biosynthesis. The metabolites from these feeds were identified by full-scan gas chromatography-mass spectrometry (GC-MS) to confirm the conversions of [²H₂]GA₂₄ to [²H₂]GA₉ and of [²H₄]GA₉ to [²H₄]GA₄. The results show that GA₄ is biosynthesized from GA₂₄ via GA₉. In a cucumber hypocotyl elongation bioassay using cv. Yomaki, prohexadione (DOCHC), an inhibitor of 2-oxoglutaratedependent dioxygenase, inhibited the hypocotyl elongation caused by application of GA₉, while DOCHC enhanced the elongation caused by application of GA₄. These results indicate that GA₄ is a physiologically active GA and that the activity of GA₉ is due to its conversion to GA₄ in cucumber shoots.     

37份新疆粳稻品种(系)的IRAP遗传多样性分析

该研究基于4个稻属(Oryza)反转录转座子,包括活性、低拷贝[Tos17/Osr21(Ty1-copia)和RIRE7/Osr31(Ty3-gypsy)]和非活性、高拷贝[Osr34(Ty3-gypsy)和Houba/Tos5/Osr13(Ty1-copia)],在两侧翼长末端重复序列(LTR)区域分别设计引物,对37份新疆粳稻(Oryza sativa L.ssp.japonica)栽培品种(系)进行PCR扩增。评估鉴定适用于反转录转座子插入位点间扩增多态性(IRAP)标记方法,并分析37份供试品种(系)的遗传多样性。(1)PCR扩增结果显示,Tos17/Osr21、RIRE7/Osr31、Osr34和Houba/Tos5/Osr13依次获得73、63、107和560条谱带,其中多态性条带36、63、70和523个,多态性比率为49.3%、100.0%、65.4%和93.4%。(2)综合评估比较多态性、异质性、总谱带数和平均多态性谱带数发现,Houba/Tos5/Osr13适用于IRAP标记方法构建DNA指纹图谱数据库。(3)以Houba/Tos5/Osr13遗传相似系数为基础,对供试品种(系)采用非加权平均(UPGMA)法进行聚类分析显示,以0.55为阈值将37份新疆粳稻栽培品种(系)分为6大类群,绝大多数品种(系)得到了明确的区分,品种间的遗传相似性较高,多样化程度偏低;品系‘20-18’和‘96-16’分别各自聚为一类,表明品系与品种间遗传背景较远,多样化程度较高。综上所述,IRAP分子标记适用于新疆粳稻种质资源的亲缘关系分析、鉴别及育种遗传距离的判定和DNA指纹图谱数据库构建等相关研究,在实际育种中选取不同类群的水稻品种与品系进行杂交选育,成功率较高,可能会大大缩短优良品种的选育进程。     

Endogenous gibberellin levels influence in-vitro shoot regeneration in Arabidopsis thaliana (L.) Heynh.

The regeneration of shoot buds from callus cells in vitro is an important technique in modern plant genetic manipulation. Whilst it is clear that genetic factors play a major role in determining the ability of callus cells to become organized into regenerating shoot buds, the precise nature of these factors remains unknown. Here we show that callus derived from mutants of Arabidopsis thaliana which have reduced levels of endogenous bioactive gibberellins (GAs), or reduced responsivity to GAs, regenerates shoot buds more readily than does callus derived from wild-type controls. In addition, exogenous GA reduces, and exogenous paclobutrazol (a GA-biosynthesis inhibitor) increases, the frequency of shoot bud regeneration from wild-type callus. These results show that GA levels play a role in regulating shoot bud regeneration from callus, and suggest that variation in endogenous GA levels or responsivity may account for a major component of the genetic variation in shoot bud regeneration frequency described in other species.     

Regulation of elongation growth by gibberellin in root segments of Lemna minor

Hormonal control of elongation growth was analyzed in segments excised from the elongation zone of Lemna roots. Exogenous GA3 did not promote the segment elongation but rather inhibited it. Uniconazole-P, a gibberellin biosynthesis inhibitor, significantly inhibited the segment elongation, and the inhibitory effect was completely nullified by GA3. In the epidermis, cell elongation was inhibited, but lateral cell expansion was not affected by uniconazole-P. Orientation of cortical microtubules of epidermal cells was disturbed by treatment with uniconazole-P for 12 h, and the disorganization of cortical microtubules was ameliorated by GA3. These findings suggested that disorganization of cortical microtubules induced inhibition of elongation growth of root. However, stabilization of cortical microtubules by taxol, a microtubule-stabilizing agent, did not affect the inhibition of segment elongation by uniconazole-P. These results suggested that endogenous gibberellin controls the elongation growth of root by regulating cell elongation.     

Cloning, expression and function of phosphate transporter encoded gene in Oryza sativa L.

OsPT6:1, a phosphate transporter encoding gene from the leaf samples of Oryza sativa, was identified through PCR with specifically designed primers. The phylogenetic analysis and the conserved amino acid residue site detection suggested OsPT6:1 a possible high-affinity phosphate transporter encoding gene. In situ hybridization and RT-PCR demonstrated the expression of OsPT6:1 in both roots and leaves. The peak expression signal was observed in mesophyll cells under low phosphorus (P) induction. A homologous recombination study indicated that OsPT6:1 can enhance the Pi uptake efficiency of Pichia pastoris. At the meantime, the introduction of OsPT6:1 was able to complement the Pi uptake function of yeast cells with high-affinity phosphate transporters deficient. Those results substantiated our contention that OsPT6:1 encoded a high-affinity phosphate transporter of Oryza sativa.     

Interconversion of gibberellin A1 to gibberellin A8 in seedlings of dwarf Oryza sativa

[³H]Gibberellin A₁ ([³H]GA₁)applied to seedlings of dwarf rice (Oryza sativa L. cv. Tanginbozu) was metabolized to GA₈. Identification of GA₈, was made by gas-liquid radiochromatography using three liquid stationary phases.     

Effect of gibberellic acid combined with saponin on shoot elongation of Asparagus officinalis

Effect of gibberellic acid (GA₃) combined with saponin on shoot elongation of Asparagus officinalis was evaluated in tissue culture. Addition of saponin to GA₃ supplemented Murashige and Skoog (MS) basal medium showed a dose depended effect on shoot length of Asparagus officinalis. However, increasing concentration of saponin above 3.0 mg dm⁻³ decreased shoot length and showed yellowing and thinning of shoots. Saponin (3.0 mg dm⁻³) + GA₃ (0.2 mg dm⁻³) mixture treated by variable duration of sonication (0, 1, 3, 5, 7, 9, 11, 13 and 15 min) were evaluated for shoot elongation on MS basal medium. The highest shoot lengths (14.4 ± 0.3 and 15.1 ± 0.1 cm) were found after 5 and 7 min sonication.     

Light intensity, gibberellin content and the resolution of shoot growth in Brassica

The role of gibberellins (GAs) in the regulation of shoot elongation is well established but the phytohormonal control of dry-matter production is poorly understood. In the present study, shoot elongation and dry-matter production were resolved by growing Brassica napus L. seedlings under five light intensities (photon flux densities) ranging from 25 to 500 μmol m⁻² s⁻¹. Under low light, plants were tall but produced little dry weight; as light intensity was increased, plants were progressively shorter but had increasing dry weights. Endogenous GAs in stems of 16- and 17-d-old plants were analyzed by gas chromatography-selected ion monitoring with [²H₂] internal standards. The contents of GAs increased dramatically with decreasing light intensity: GA₁, GA₃, GA₈ and GA₂₀ were 62, 15, 16 and 32 times higher, respectively, under the lowest versus highest light intensities. Gibberellin A₁₉ was not measured at 25 μmol m⁻² s⁻¹ but was 9␣times greater in the 75 compared to 500 μmol m⁻² s⁻¹ treatment. Shoot and hypocotyl lengths were closely positively correlated with (log) GA concentration (for example: r ² = 0.93 for GA₁ and hypocotyl length) but shoot dry matter was negatively correlated with GA concentration. The application of gibberellic acid (GA₃) produced elongation of plants grown under high light, indication that their low level of endogenous GA was limiting shoot elongation. Although endogenous GA₂₀ showed the greatest influence of light treatment, metabolism of [³H]GA₂₀ and of [³H]GA₁ was only slightly influenced by light intensity, suggesting that neither 2β- nor 3β-hydroxylation were points of metabolic regulation. The results of this study indicate that GAs control shoot elongation but are not directly involved in the regulation of shoot dry weight in Brassica. The study also suggests a role of GAs in photomorphogenesis, serving as an intermediate between light condition and shoot elongation response. Received: 18 June 1998 / Accepted: 29 July 1998