拟南芥属与盐芥属的亲缘关系:叶表皮和分子证据

观察了拟南芥属、盐芥属以及相关属的叶表皮微形态特征,并测定了叶绿体DNA的trnL内含子和trnL-F基因间隔区序列,对这两个属的亲缘关系进行了比较研究。研究结果初步表明:盐芥属与拟南芥属之间的亲缘关系较远,前者应置于大蒜芥族,与该族中的山嵛菜属关系最近;后者则应放在南芥族而不是大蒜芥族。     

基于种皮形态和叶绿体trnL-F对菘蓝属（十字花科）的系统学位置研究

利用种皮微形态观察与叶绿体DNA的trnL内含子和trnL-F基因间隔区序列测定分析相结合,对十字花科菘蓝属植物及其相关属种的系统学关系进行了探讨.研究结果表明原属独行菜族的菘蓝属植物,其种皮特征与原属鸟头荠族的舟果荠属植物相似,同属一类型.而与独行菜族的模式属独行菜属植物、大蒜芥族的模式属大蒜芥属植物以及鸟头荠族的模式属鸟头荠属植物种皮微形态差异显著;在基于叶绿体DNA的trnL内含子和trnL-F基因间隔区序列所构建的系统发育树中,菘蓝属植物与舟果荠属植物距离最近,而与独行菜属、大蒜芥属、鸟头荠属植物具有一定的间隔,结合形态特征,本研究认为,菘蓝属与舟果荠属植物具有较近的亲缘关系,而不是同族的独行菜属植物.     

中国独行菜族(十字花科)部分属种的分子系统学研究

利用叶绿体DNA的trnL内含子和trnL-F基因间隔区序列测定,对中国独行菜族部分属及相关属植物进行了分子系统学研究,结果表明:独行菜族是多系类群,在分子树中,所研究的中国独行菜族部分属植物被分别聚在了3个不同的并列系中,其中,荠属(Capsella)和亚麻荠属(Camelina)与南芥族的3个属聚在系Ⅰ,认为应将二者分别从独行菜族和大蒜芥族中移出,划入南芥族中;菥蓂属(Thlaspi)和菘蓝属(Isatis)与大蒜芥族的3个属聚成系Ⅱ,支持将二者移出独行菜族,划入大蒜芥族的观点;独行菜属(Lepidium)、臭荠属(Coronopus)和群心菜属(Cardaria)三者关系密切,组成系Ⅲ,其中臭荠嵌入独行菜属中,支持将臭荠属合并到独行菜属的处理意见.     

拟南芥属的系统位置: 种皮及分子证据

拟南芥属(Arabidopsis (L.) Heynhold)拥有现代分子生物学研究的模式植物拟南芥(A. thaliana (L.) Heynhold), 但其属的系统位置及与近缘属关系争议较大。根据对拟南芥属及其相关属种的种皮微形态观察, 结合测定分析各属种叶绿体DNA的trnL内含子和trnL-F基因间隔区序列, 结果表明, 拟南芥属的近缘属种包括荠属(Capsella Medic.)、亚麻荠属(Camelina (L.)Crantz)、须弥芥属(Crucihimalaya Al-Shehbaz et al.)、无苞芥属(Olimarabidopsis Al-Shehbaz et al.)、旗杆芥属(Turritis L.)、南芥属(Arabis L.)和糖芥属(Erysimum Kitagawa)。     

山白树属及其近缘属聚类分析

运用系统聚类分析法,对山白树属及其近缘属进行定量分析,结果表明山白树属与牛鼻栓属亲缘关系密切,可组成一族,该族与蚊母树族有着较近的亲缘。     

大蒜芥属一新变种

发表了大蒜芥属一新变种,无毛全叶大蒜芥(Sisymbrium luteum (Maxim.)O. E. Schulz var. glabrum F. Z. Li et Z. Y. Sun.)。     

拟南芥属的系统位置：种皮及分子证据

拟南芥属（Arabidopsis（L.）Heynhold）拥有现代分子生物学研究的模式植物拟南芥（A.thaliana（L.）Heynhold）,但其属的系统位置及与近缘属关系争议较大。根据对拟南芥属及其相关属种的种皮微形态观察,结合测定分析各属种叶绿体DNA的trnL内含子和trnL-F基因间隔区序列,结果表明,拟南芥属的近缘属种包括荠属（Capsella Medic.）、亚麻荠属（Camelina（L.）Crantz）、须弥芥属（Crucihimalaya Al-Shehbaz et al.）、无苞芥属（Olimarabidopsis Al-Shehbaz et al.）、旗杆芥属（Turritis L.）、南芥属（Arabis L.）和糖芥属（Erysimum Kitagawa）。     

盐胁迫对拟南芥和盐芥莲座叶芥子油苷含量的影响

芥子油苷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。以模式植物拟南芥（Arabidopsis thaliana）和盐生模式植物盐芥（Thellungiella halophila）为研究对象,系统地分析了盐胁迫下二者芥子油苷组成和含量的变化规律。拟南芥（生长4周）和盐芥（生长6周）叶片的芥子油苷组成在盐胁迫后没有改变。拟南芥的芥子油苷总量、脂肪族芥子油苷总量、吲哚族芥子油苷总量受盐胁迫的影响均不显著,而盐芥的则随盐胁迫增强先减少、后增加并高于对照水平。拟南芥脂肪族的3MSOP、5MSOP和吲哚族的4OHI3M、4MOI3M随盐胁迫增强而含量降低,而脂肪族的6MSOH、吲哚族的I3M以及盐芥脂肪族的3MSOP则随盐胁迫增强有含量增加的趋势。拟南芥脂肪族的8MSOO和吲哚族的1MOI3M,盐芥脂肪族的3MTP、Allyl、10MSD和吲哚族的4MOI3M,在盐胁迫下的含量变化与盐芥芥子油苷总量的变化趋势一致。     

辣根属和豆瓣菜属(十字花科)系统位置的分子证据

对十字花科葶苈族的辣根属、南芥族的豆瓣菜属及相关属种植物的叶绿体DNA的trnL内含子和trnL-F基因间隔区序列进行了测定分析。结果表明,辣根属植物与南芥族的山芥属、蔊菜属、豆瓣菜属、碎米荠属在系统发育树中聚成一支,与葶苈族的模式属葶苈属植物相隔较远,结合形态特征,本研究认为辣根属应从葶苈族移出,其系统位置应靠近山芥属、蔊菜属、豆瓣菜属、碎米荠属植物;此外,系统发育树中,豆瓣菜属植物并入碎米荠属中,表明二者具有更近的亲缘关系,本研究结果不支持《中国植物志》第33卷对辣根属和豆瓣菜属的系统位置的处理。     

中国大蒜芥属（十字花科）叶表皮微形态学研究

利用光学显微镜观察了中国十字花科大蒜芥属9种1变种植物的叶表皮形态。结果表明：中国大蒜芥属植物叶上表皮细胞通常为多边形,垂周壁平直或弓形,少有稍浅波状,叶下表皮细胞为不规则形,垂周壁波状或深波状;气孔器类型均以不等细胞型为主,少有无规则型,偶有平列型。依据叶表皮特征,可将中国大蒜芥属划分为三种类型：（1）叶上表皮无气孔分布或偶见;（2）叶上表皮气孔常明显几个聚成一簇或排成短列,气孔密度小于叶下表皮;（3）叶上表皮气孔比较均匀分布,气孔密度与叶下表皮近相似。     

The Arabidopsis halophytic relative Thellungiella halophila tolerates nitrogen-limiting conditions by maintaining growth, nitrogen uptake, and assimilation

A comprehensive knowledge of mechanisms regulating nitrogen (N) use efficiency is required to reduce excessive input of N fertilizers while maintaining acceptable crop yields under limited N supply. Studying plant species that are naturally adapted to low N conditions could facilitate the identification of novel regulatory genes conferring better N use efficiency. Here, we show that Thellungiella halophila, a halophytic relative of Arabidopsis (Arabidopsis thaliana), grows better than Arabidopsis under moderate (1 mm nitrate) and severe (0.4 mm nitrate) N-limiting conditions. Thellungiella exhibited a lower carbon to N ratio than Arabidopsis under N limitation, which was due to Thellungiella plants possessing higher N content, total amino acids, total soluble protein, and lower starch content compared with Arabidopsis. Furthermore, Thellungiella had higher amounts of several metabolites, such as soluble sugars and organic acids, under N-sufficient conditions (4 mm nitrate). Nitrate reductase activity and NR2 gene expression in Thellungiella displayed less of a reduction in response to N limitation than in Arabidopsis. Thellungiella shoot GS1 expression was more induced by low N than in Arabidopsis, while in roots, Thellungiella GS2 expression was maintained under N limitation but was decreased in Arabidopsis. Up-regulation of NRT2.1 and NRT3.1 expression was higher and repression of NRT1.1 was lower in Thellungiella roots under N-limiting conditions compared with Arabidopsis. Differential transporter gene expression was correlated with higher nitrate influx in Thellungiella at low (15)NO(3)(-) supply. Taken together, our results suggest that Thellungiella is tolerant to N-limited conditions and could act as a model system to unravel the mechanisms for low N tolerance.     

Genomes of extremophile crucifers: new platforms for comparative genomics and beyond

ABSTRACT: Recent reports describe the genome sequencing of Thellungiella salsuginea and Thellungiella parvula, two extremophile crucifers closely related to the stress-sensitive model plant Arabidopsis thaliana.     

Metabolome and water homeostasis analysis of Thellungiella salsuginea suggests that dehydration tolerance is a key response to osmotic stress in this halophyte

Thellungiella salsuginea, a Brassicaceae species closely related to Arabidopsis thaliana, is tolerant to high salinity. The two species were compared under conditions of osmotic stress to assess the relationships between stress tolerance, the metabolome, water homeostasis and growth performance. A broad range of metabolites were analysed by metabolic fingerprinting and profiling, and the results showed that, despite a few notable differences in raffinose and secondary metabolites, the same metabolic pathways were regulated by salt stress in both species. The main difference was quantitative: Thellungiella had much higher levels of most metabolites than Arabidopsis whatever the treatment. Comprehensive quantification of organic and mineral solutes showed a relative stability of the total solute content regardless of the species or treatment, meaning that little or no osmotic adjustment occurred under stress. The reduction in osmotic potential observed in plants under stress was found to result from a passive loss of water. Thellungiella shoots contain less water than Arabidopsis shoots, and have the ability to lose more water, which could contribute to maintain a water potential gradient between soil and plant. Significant differences between Thellungiella and Arabidopsis were also observed in terms of the physicochemical properties of their metabolomes, such as water solubility and polarity. On the whole, the Thellungiella metabolome appears to be more compatible with dehydration. Osmotic stress was also found to impact the metabolome properties in both species, increasing the overall polarity. Together, the results suggest that Thellungiella copes with osmotic stress by tolerating dehydration, with its metabolic configuration lending itself to osmoprotective strategies rather than osmo-adjustment.     

The Arabidopsis‐related halophyte Thellungiella halophila: boron tolerance via boron complexation with metabolites?

Tolerance to boron (B) is still not completely understood. We tested here the hypothesis that Thellungiella halophila, an Arabidopsis thaliana-related 'extremophile' plant, with abundance of B in its natural environment, is tolerant to B, and examined the potential mechanisms of this tolerance. With 1-10 mm B applied ([B](ext)) to Thellungiella and Arabidopsis grown in hydroponics, the steady-state accumulated B concentration ([B](int)) in the root was below [B](ext), and was similar in both, suggesting both extrude B actively. Whether grown in soil or hydroponically, the shoot [B](int) was higher in Arabidopsis than in Thellungiella, suggesting more effective net B exclusion by Thellungiella root. Arabidopsis exhibited toxicity symptoms including reduced shoot fresh weight (FW), but Thellungiella was not affected, even at similar levels of shoot-accumulated [B](int) (about 10 to 40 mm B in 'shoot water'), suggesting additional B tolerance mechanism in Thellungiella shoot. At [B](ext) = 5 mm, the summed shoot concentration of the potentially B-binding polyhydroxyl metabolites (malic acid, fructose, glucose, sucrose and citric acid) in Arabidopsis was below [B](int) , but in Thellungiella it was over twofold higher than [B](int) , and therefore likely to allow appreciable 1:2 boron-metabolite complexation in the shoot. This, we suggest, is an important component of Thellungiella B tolerance mechanism.     

Effect of salt stress on growth and osmotic regulation in Thellungiella and Arabidopsis callus

The response of Thellungiella (Thellungiella holophila) and Arabidopsis (Arabidopsis thaliana) callus to salt stress was investigated. The relative growth rate of Arabidopsis calli decreased with increased levels of NaCl. However, the relative growth rate of Thellungiella calli increased with higher levels of NaCl, reaching maximal growth at 100 mM NaCl, but then subsequently declined. A similar pattern of accumulation of proline, glycine betaine, and total flavonoid was observed; whereas, accumulation of treholase continued to increase with increasing NaCl levels in both Thellungiella and Arabidopsis calli. Overall, with increasing NaCl levels, accumulation of glycine betaine, total flavonoid, and treholase was higher in Thellungiella than in Arabidopsis calli; while, proline and sucrose contents were higher in Arabidopsis than in Thellungiella calli. These results indicated that compatible solutes were involved in the response of plant calli to salt stress, and that the halophyte Thellungiella and glycophyte Arabidopsis selected different compatible solutes to adapt to salt stress environments. X. Zhao and H. J. Tan have contributed equally to the paper.