Saussurea involucrata (Snow Lotus) ICE1 and ICE2 Orthologues Involved in Regulating Cold Stress Tolerance in Transgenic Arabidopsis.

As with other environmental stresses, cold stress limits plant growth, geographical distribution, and agricultural productivity. CBF/DREB (CRT-binding factors/DRE-binding proteins) regulate tolerance to cold/freezing stress across plant species. ICE (inducer of CBF expression) is regarded as the upstream inducer of CBF expression and plays a crucial role as a main regulator of cold acclimation. Snow lotus (Saussurea involucrata) is a well-known traditional Chinese herb. This herb is known to have greater tolerance to cold/freezing stress compared to other plants. According to transcriptome datasets, two putative ICE homologous genes, SiICE1 and SiICE2, were identified in snow lotus. The predicted SiICE1 cDNA contains an ORF of 1506 bp, encoding a protein of 501 amino acids, whereas SiICE2 cDNA has an ORF of 1482 bp, coding for a protein of 493 amino acids. Sequence alignment and structure analysis show SiICE1 and SiICE2 possess a S-rich motif at the N-terminal region, while the conserved ZIP-bHLH domain and ACT domain are at the C-terminus. Both SiICE1 and SiICE2 transcripts were cold-inducible. Subcellular localization and yeast one-hybrid assays revealed that SiICE1 and SiICE2 are transcriptional regulators. Overexpression of SiICE1 (35S::SiICE1) and SiICE2 (35S::SiICE2) in transgenic Arabidopsis increased the cold tolerance. In addition, the expression patterns of downstream stress-related genes, CBF1, CBF2, CBF3, COR15A, COR47, and KIN1, were up-regulated when compared to the wild type. These results thus provide evidence that SiICE1 and SiICE2 function in cold acclimation and this cold/freezing tolerance may be regulated through a CBF-controlling pathway.

Repellent activities of essential oils rich in sesquiterpenoids from Saussurea amara (L.) DC. and Sigesbeckia pubescens Makino against two stored-product insects.

The essential oils (EOs) from aerial parts of Saussurea amara (L.) DC. (SAEO) and Sigesbeckia pubescens Makino (SPEO) were analyzed for their chemical composition by GC-MS, and their repellent activities against adults of the red flour beetle, Tribolium castaneum Herbst, as well as the booklouse, Liposcelis bostrychophila Badonnel, were evaluated for the first time. Results of GC-MS analysis indicated that both SAEO and SPEO were characterized by high content of sesquiterpenoids (relative content > 70%) including oxygenated sesquiterpenoids. The two oil samples and their major component caryophyllene oxide exerted beneficial repellent effects on T. castaneum and L. bostrychophila at 2 and 4 h post-exposure. At 4 h post-exposure, the PR value of caryophyllene oxide could still reach 92% (class V) against T. castaneum at minimum testing concentration of 3.15 nL/cm2, and this compound was observed to result in the greatest repellency (PR = 100%) against L. bostrychophila at 12.63 nL/cm2. This work confirmed the potent repellent efficacy of SAEO and SPEO for controlling pest damage and suggested their potential to be developed into botanical repellents.

[Altitudinal variation of floral organs in Saussurea przewalskii and its relationship with the number and mass of seeds]. / å¼¯é½¿é£Žæ¯›èŠèŠ±éƒ¨å™¨å®˜çš„æµ·æ‹”å˜å¼‚åŠå ¶ä¸Žç§å­è´¨é‡å’Œæ•°ç›®çš„å ³ç³».

We examined the variation of floral organs of Sausssurea przewalskii along altitude and its relationship with the number and mass of seeds from 12 populations in the northeastern edge of Qinghai-Tibetan Plateau, China. At the altitude of 3500-4500 m, the filament length, anther length, column length and style branch length were 0.52-1.01, 0.23-0.63, 0.74-1.58, and 0.11-0.22 cm, respectively. All the indices significantly increased with altitude, while the number of pollens (26.5×104-73.5×104) significantly decreased. There was a significant negative correlation between the lengths of filament, style, column branches and pollen numbers, and a significant positive correlation between column length and filament length. The number of seeds was negatively correlated with the lengths of filament, column and style branches, but positively correlated with the number of pollen. The hundred kernals weight was positively correlated with the length of the filament, column and style branches, and negatively correlated with the number of pollen. With the increases of altitude, S. przewalskii extends the length of flower organs to increase the pollen carrying capacity and input of insects in the flowering period, and produces large seeds with more competitive advantage and survival rate in fruiting stage to improve its fitness.

[Effects of altitude on the reproductive characteristics of Saussurea przewalskii at the eastern margin of the Tibetan Plateau, China.] / 海拔对青藏高原东缘弯齿风毛菊繁殖特征的影响.

The paper studied the effects of altitude on reproductive characteristics in 12 populations of Saussurea przewalskii at the eastern Qinhai-Tibetan Plateau, China. The results showed that the size, reproductive organ biomass, vegetative organ biomass, capitulum number, and seed number of individual plant decreased with the increasing altitude, and the capitulum mass and hundred-grain mass increased continuously. S. przewalskii could ensure its reproduction by reducing plant body size to decrease resource consumption, and increasing the allocation of limit resources to flower biomass. In order to ensure sexual reproduction, the reproductive allocation of the plants increased with increasing the altitude. There was a trade-off between capitulum number and capitulum mass, and between seed number and hundred-grain mass, which allowed the plants to maximize their fitness under stressful conditions.

[Population characteristics and ecological suitability of Saussureae hieracioides].

OBJECTIVE: To analyze the population characteristics and the appropriate producing area of Saussureae hieracioides in China. METHODS: Chuanxibei plateau, one of the main producing areas of Saussureae hieracioides, was selected as the analytical basal place. Ecological methods were used to investigate the density and biomass of Saussureae hieracioides. Traditional Chinese Medicine Geographic Information System (TCMGIS-II) was used to analyze the appropriate producing area of Saussureae hieracioides. RESULTS: Saussureae hieracioides could form the dominant species in its distribution area. The proper region (with similarity of 90% - 100%) of Saussureae hieracioides accounted for 338 776.89 km2, including 5 provinces/municipalities and 226 counties/cities. The largest area among them was Tibet Autonomous Region with area of 148 175.55 km2, followed by Sichuan Province (110 216.46 km2), Qinghai Province (62 947.61 km2), Gansu Province (16 233.09 km2) and Yunnan Province (1 177.18 km2). CONCLUSION: TCMGIS is much valuable to the recognition of formation of producing area, the division of adaptive area, introduction and acclimatization of medicinal materials, it also provides a scientific reference for the introduction and cultivation of Saussureae hieracioides.

Cloning and characterization of a novel dehydrin gene, SiDhn2, from Saussurea involucrata Kar. et Kir.

Saussurea involucrata Kar. et Kir. is a hardy dicotyledonous plant capable of tolerating severe abiotic stress conditions. In a previous study, we created a cDNA library to determine what factors are associated with the cold acclimation response in S. involucrata. From this, a full-length cDNA of a dehydrin-like gene (SiDhn2) was obtained by RT-PCR. The SiDhn2 gene was characterized in this study. The full-length SiDhn2 cDNA comprised 693 bp containing an open reading frame of 345 bp specifying a protein of 115 amino acids. An alignment of the deduced amino acid sequence showed that SiDhn2 shared 55 % identity with two Brassica dehydrins. Agrobacterium tumefaciens was used to transform RD29A:SiDhn2 and 35S:SiDhn2 constructs into tobacco to investigate the germination and resistance to freezing and drought stress of transgenic plants. The RD29A:SiDhn2 transgenic plants showed greater resistance to freezing and drought stress than 35S:SiDhn2 transgenic plants or the wild-type. This study demonstrates that SiDhn2 confers cold hardiness and drought resistance, and may be a candidate resistance gene for genetic improvement of crops to increase stress resistance.

Effect of lanthanum on rooting of in vitro regenerated shoots of Saussurea involucrata Kar. et Kir.

In present study, the effect of lanthanum (La) on the rooting of regenerated shoots of Saussurea involucrata Kar. et Kir was analyzed. Rooting occurred from regenerated shoots inoculated on a medium supplemented with La, the plant rooting hormone indole-3-acetic acid (IAA), or both La and IAA together. The highest rooting efficiency (96%), root number/shoot (8.5), and root length (63 mm) were recorded in shoots cultured on medium containing 2.5 µM IAA combined with 100 µM La(3+). In order to elucidate the mechanism of rooting enhancement by La, we examined dynamic changes in antioxidant enzyme activities in plant tissue over time in culture. We found that the activities of peroxidase (POX) and superoxide dismutase (SOD) were significantly higher in plant tissue cultured in IAA plus La than in La or IAA alone. At the same time, the highest H(2)O(2) content was detected in plant tissue in the presence of 2.5 µM IAA plus 100 µM La(3+). In light of these data and previous results, we speculate that La enhanced IAA-induced rooting by acting as a mild abiotic stress to stimulate POX and SOD activities in plant cells. Then, IAA reacted with oxygen and POX to form the ternary complex enzyme-IAA-O(2) that dissociated into IAA radicals and O(2)(-). Subsequently, IAA-induced O(2)(-) readily converted to hydroxyl radical (HO·) via SOD-catalyzed dismutation. Finally, cell wall loosening and cell elongation occurred as a consequence of HO-dependent scission of wall components, leading to root growth. The treatment of IAA combined with La resulted in the highest plantlet survival (80%) compared to single treatments with IAA or La alone. These data suggest that rare earth elements enhance root morphogenesis and the growth of S. involucrata.

[Effects of short-term enhanced UV-B radiation on the PS II photochemical efficiency of alpine plant Saussurea superba].

A simulation experiment of short-term supplementation of UV-B was conducted to study the changes of chlorophyll fluorescence coefficients of alpine plant Saussurea superba under three typical weather conditions (sunny, cloudy, and shady) in Qinghai-Tibet Plateau. When the weather changed from sunny to shady, the maximal quantum efficiency of PS II photochemistry (F(v)/F(m)) after 3 minutes of dark adaptation increased significantly, the actual photochemical efficiency of PS II (phi(PS II)) and photochemical quenching (q(P)) also increased, but the non-photochemical quenching (NPQ) decreased, demonstrating that PAR was the main factor affecting the PS II photochemical efficiency of S. superba. After the short-term supplementation of UV-B, the F(v)/F(m) and NPQ under the three typical weather conditions had a slight decrease but the phi(PS II) and q(P) had a slight increase, while the photosynthetic gas exchange had less change. The increasing trend of net photosynthetic rate P(n) and psi(PS II) under enhanced UV-B radiation could be related to the existence of more UV-A component, and also, benefited from the increased leaf thickness. UV-B radiation had potential negative effects on leaf photosynthetic components.

[Effects of strong solar UV-B radiation on photosynthesis and photosynthetic pigment contents of Saussurea superba on Qinghai-Tibet Plateau].

Taking the main companion species Saussurea superba in an alpine Kobresia humilis meadow on Qinghai-Tibet Plateau as test material, a UV-B exclusion experiment with UV-B excluding and UV-B transmitting filters was performed to study the effects of strong solar UV-B on the photosynthesis, photosynthetic pigments, and UV-B-absorbing compounds of S. superba, aimed to examine the adaptation capability of alpine plants to strong solar UV-B radiation. The removal of UV-B components from natural sunlight increased the net photosynthetic rate (P < 0.05) and PS II photochemistry efficiency of S. superba. The relatively increased leaf thickness under ambient UV-B could compensate the photo-oxidation of photosynthetic pigments, an inherent characteristic of alpine plants growing in intense UV-B. Short-term removal of UV-B radiation had no obvious effects on the UV-B-absorbing compounds, suggesting that these compounds in epidermal layer of S. superba could hardly be affected by the environment. It was concluded that the increase of photosynthetic pigment contents due to the enhancement of leaf thickness was a specious phenomenon, but the strong solar UV-B radiation on Qinghai-Tibet Plateau still had a potential negative impact on the photo-physiological processes in alpine plant S. superba.

Plant adaptation to frequent alterations between high and low temperatures: remodelling of membrane lipids and maintenance of unsaturation levels.

One major strategy by which plants adapt to temperature change is to decrease the degree of unsaturation of membrane lipids under high temperature and increase it under low temperature. We hypothesize that this strategy cannot be adopted by plants in ecosystems and environments with frequent alterations between high and low temperatures, because changes in lipid unsaturation are complex and require large energy inputs. To test this hypothesis, we used a lipidomics approach to profile changes in molecular species of membrane glycerolipids in two plant species sampled from alpine screes and in another two plant species grown in a growth chamber, with the temperature cycling daily between heat and freezing. We found that six classes of phospholipid and two classes of galactolipid showed significant changes, but the degree of unsaturation of total lipids and of three lysophospholipid classes remained unchanged. This pattern of changes in membrane lipids was distinct from that occurring during slow alterations in temperature. We propose two types of model for the adaptation of plants to temperature change: (1) remodelling of membrane lipids but maintenance of the degree of unsaturation are used to adapt to frequent temperature alterations; and (2) both remodelling and changes in the degree of unsaturation to adapt to infrequent temperature alterations.

[Effects of cold-hardening on freezing tolerance and antioxidant enzyme activities in plantlets of Saussurea laniceps Hand.-Mazz].

Living conditions for plants in the mountains become increasingly less favorable with increasing altitude. In the alpine region, the plants are commonly exposed to daily rather than seasonal temperature fluctuations and by frequent freezing temperature. To elucidate the freezing tolerance mechanism of alpine plants, Saussurea laniceps Hand.-Mazz. was used as a model plant. It is a perennial herbal plant distributed in alpine regions of Yunnan and Tibet of China. It can survive on mountains with elevations over 4000 m. Wild S. laniceps plants are propagated only by seeds in the alpine areas. Micropropagation of S. laniceps through seed was a desirable method to get enough seedlings for freezing research. Micropropagation through plantlets derived from germinated S. laniceps seeds collected from Tibet was achieved successfully. Activities of antioxidant enzyme and solute contents were investigated in plantlets of S. laniceps. Freezing tolerance in plantlets increased after 7 or 15 d of cold-hardening (Table 1). Cold-hardening (2 degrees C) increased the activities of SOD, peroxidase, and catalase (Fig.1) in plantlets. A similar increase was also observed in the protein and proline content (Fig.1), whereas soluble carbohydrates changed little (Fig.1). These results obtained suggest that the higher activities of SOD, peroxidase, and catalase, as well as the higher protein and proline content may be biochemical adaptation for freezing toleranc in cold-hardened S. laniceps plantlets. Interestingly, deacclimation was slow; even after the plants were placed again under a temperature of 21-23 degrees C for 5 d, the higher freezing hardiness, enzyme activities, protein and proline content acquired after cold acclimation remained. In conclusion, our plantlet cultures have proved to be good materials for experimentation on freezing resistance in study of freezing-resistance mechanism in the alpine plant S. laniceps.