Involvement of lipid transfer proteins in resistance against a non-host powdery mildew in Arabidopsis thaliana

Non-specific lipid transfer proteins (LTPs) are involved in the transport of lipophilic compounds to the cuticular surface in epidermal cells and in the defence against pathogens. The role of glycophosphatidylinositol (GPI)-anchored LTPs (LTPGs) in resistance against non-host mildews in Arabidopsis thaliana was investigated using reverse genetics. Loss of either LTPG1, LTPG2, LTPG5 or LTPG6 increased the susceptibility to penetration of the epidermal cell wall by Blumeria graminis f. sp. hordei (Bgh). However, no impact on pre-penetration defence against another non-host mildew, Erysiphe pisi (Ep), was observed. LTPG1 was localized to papillae at the sites of Bgh penetration. This study shows that, in addition to the previously known functions, LTPGs contribute to pre-invasive defence against certain non-host powdery mildew pathogens.     

Nutrient addition does not increase the benefits of clonal integration in an invasive plant spreading from open patches into plant communities

• One benefit of clonal integration is that resource translocation between connected ramets enhances the growth of the ramets grown under stressful conditions, but whether such resource translocation reduces the performance of the ramets grown under favourable conditions has not produced consistent results. In this study, we tested the hypothesis that resource translocation to recipient ramets may reduce the performance of donor ramets when resources are limiting but not when resources are abundant.
• We grew Mikania micrantha stolon fragments (each consisting of two ramets, either connected or not connected) under spatially heterogeneous competition conditions such that the developmentally younger, distal ramets were grown in competition with a plant community and the developmentally older, proximal ramets were grown without competition. For half of the stolon fragments, slow‐release fertiliser pellets were applied to both the distal and proximal ramets.
• Under both the low and increased soil nutrient conditions, the biomass, leaf number and stolon length of the distal ramets were higher, and those of the proximal ramets were lower when the stolon internode was intact than when it was severed. For the whole clone, the biomass, leaf number and stolon length did not differ between the two connection treatments. Connection did not change the biomass of the plant communities competing with distal ramets of M. micrantha.
• Although clonal integration may promote the invasion of M. micrantha into plant communities, resource translocation to recipient ramets of M. micrantha will induce a cost to the donor ramets, even when resources are relatively abundant.

     

Investigating seed dormancy in cotton (Gossypium hirsutum L.): understanding the physiological changes in embryo during after‐ripening and germination

• The dormancy of seeds of upland cotton can be broken during dry after‐ripening, but the mechanism of its dormancy release remains unclear.
• Freshly harvested cotton seeds were subjected to after‐ripening for 180 days. Cotton seeds from different days of after‐ripening (DAR) were sampled for dynamic physiological determination and germination tests. The intact seeds and isolated embryos were germinated to assess effects of the seed coat on embryo germination. Content of H₂O₂ and phytohormones and activities of antioxidant enzymes and glucose‐6‐phosphate dehydrogenase were measured during after‐ripening and germination.
• Germination of intact seeds increased from 7% upon harvest to 96% at 30 DAR, while embryo germination improved from an initial rate of 82% to 100% after 14 DAR. Based on T₅₀ (time when 50% of seeds germinate) and germination index, the intact seed and isolated embryo needed 30 and 21 DAR, respectively, to acquire relatively stable germination. The content of H₂O₂ increased during after‐ripening and continued to increase within the first few hours of imbibition, along with a decrease in abscisic acid (ABA) content. A noticeable increase was observed in gibberellic acid content during germination when ABA content decreased to a lower level. Coat removal treatment accelerated embryo absorption of water, which further improved the accumulation of H₂O₂ and changed peroxidase content during germination.
• For cotton seed, the alleviation of coat‐imposed dormancy required 30 days of after‐ripening, accompanied by rapid dormancy release (within 21 DAR) in naked embryos. H₂O₂ acted as a core link between the response to environmental changes and induction of other physiological changes for breaking seed dormancy.

     

Variations in carbon source–sink relationships in subalpine fir across elevational gradients

• Cold‐adapted trees display acclimation in both carbon source and carbon sink capacity to low‐temperature stress at their upper elevational range limits. Hence a balanced carbon source–sink capacity might be required for their persistence and survival at the elevational tree limits.
• The present study examined the spatial dynamics of carbon source–sink relationship in subalpine fir (Abies fargesii) trees along elevational gradients in the northern slope of the temperate region and in the southern slope of the subtropics in terms of climate in the Qinling Mountain range, north‐central China.
• The results showed that non‐structural carbohydrate (NSC) concentrations in both the source and sink tissues increased with the increase in elevation. The ratio of carbon source–sink displayed a consistent decreasing trend with the increase in elevation and during growing season, showing that it was lowest at a ratio of 2.93 in the northern slope and at a ratio of 2.61 in the southern slope at the upper distribution elevations in the late growing season. Such variations of carbon source–sink ratio might be attributable to the balance between carbon source and sink activities, which changed seasonally across the elevational distribution range.
• We concluded that a ratio of carbon source–sink of at least 2.6 might be essential for subalpine fir trees to persist at their upper range limits. Therefore, a sufficient source–sink ratio and a balanced source–sink relationship might be required for subalpine fir trees to survive and develop at their upper elevational distribution limits.

     

RELATIONSHIPS BETWEEN REPRODUCTION ACTIVITIES OF FISHES WITH DRIFTING EGGS AND ENVIRONMENTAL FACTORS IN THE CHISHUI RIVER北大核心CSCD

The Chishui River is the only undammed first-order tributary of the upper Yangtze River Basin. It is an important part of the “National Nature Reserve for Rare and Endemic Fishes of the Upper Yangtze River”, which plays important roles in fish conservation. To determine main environmental factors that affect the breeding activities of fishes with drifting eggs in this river, investigations on fish resources of early life stages were carried out in Chishui Reach from March to July in 2015 and April to August in 2016. A total of 27 species of fish early resources, belonging to 3 orders, 7 families and 22 genera, were collected during the investigation period. Nine of these species Pseudolaubuca engraulis, Squalidus argentatus, Gobiobotia filifer, Botia superciliaris, Parabotia fasciata, Parabotia bimaculata, Leptobotia elongate, Leptobotia taeniops and Lepturichthys fimbriata laid drifting eggs in the running water. Canonical Correspondence Analysis (CCA) revealed various breeding environmental requirements for these species. Specially, B. superciliari, P. fasciata, P. bimaculata, L. elongate, L. taeniops and L. fimbriata tended to lay eggs when the water discharge was increasing, while P. engraulis and S. argentatus showed an opposite trend. Additionally, G. filifer preformed differently between 2015 and 2016. In the low flow year, their reproductive activities were positively associated with the water discharge. However, in the high flow year, no significant relation between the reproduction activities and water discharge was observed. These results strengthen our understanding of reproductive behavior of different fish species and provide valuable insights into fish conservation. © 2019, Institute of Hydrobiology, Chinese Academy of Sciences. All rights reserved.     

THE YANGTZE RIVER-FLOODPLAIN ECOSYSTEM: MULTIPLE THREATS AND HOLISTIC CONSERVATION北大核心CSCD

The Yangtze (Changjiang) river-floodplain is one of the most important ecosystems in China and the world, but is seriously threatened by multiple stresses. Thus, it is crucial and urgent to rehabilitate and conserve the river-floodplain. This paper reviews ecological studies conducted on the Yangtze river-floodplain, and presents suggestions for conservation and rehabilitation. First, basic concepts and research advances of riverscape and hydrological connectivity are introduced. Second, the history and current status of the Yangtze River system are summarized. Before 23 Ma, the Yangtze River cut through the Three Gorges, forming the river much like the modern one. Numerous rivers, streams, lakes (the total area 15770 km2 at present) and wetlands are distributed in the mid-lower Yangtze river-flood-plain. Such a river-lake complex ecosystem holds a unique and diverse biota, and is the most important fishery area of China. Third, main threats to the Yangtze river-floodplain ecosystem are identified, i.e., a) habitat loss, including river channelization, sharp shrinkage of lake area (ca. 10000 km2 since the 1950s), degradation of lakeshore zones and sand over-mining; b) alternations of hydrological regimes, including construction of ca. 47000 reservoirs and disconnection of most lakes from the mainstem; c) water pollution, including eutrophication, heavy metals, organic pollutants and microplastic; d) overexploitation of biological resources, including overfishing and intensive pen culture. Fourth, effects of river-lake disconnection on lake ecosystems are summarized. It was found that a) disconnection is one of the main causes of lake eutrophication; b) species diversity, biomass, production of macrophytes and macrobenthos reach maxima at some levels of intermediate river connectivity; c) disconnection greatly reduces fish species richness of each habitat guild, and natural fish larvae is severely depleted; d) disconnection simplifies macroinvertebrate food web structure, and trophic basis is more heavily relied on detritus in disconnected lakes. Last, conservation strategies are proposed. Since the Yangtze river-floodplain is a huge integrated system, the biodiversity conservation must be conducted on the whole basin scale. By establishing species-area models of fishes, the minimum protected area of Yangtze-connected lakes is estimated to be ca. 14400 km2. It means that at least 8900 km2 of disconnected lakes should be reconnected with the Yangtze mainstem, and ecohydrological operation of dams and sluices is the feasible approach. Based upon our studies on environmental flow requirements, the following measures are suggested: a) lower water levels during spring to improve germination of macrophytes, and control rising rates of water levels during spring-summer to ensure development of macrophytes; b) open sluice gates to restore migration routes for juveniles migrating into lakes during April-September, and for adults migrating back to the Yangtze mainstem during November-December. © 2019, Institute of Hydrobiology, Chinese Academy of Sciences. All rights reserved.     

SPATIAL DISTRIBUTION OF ZOOPLANKTON IN THE MAIN STEM OF THE MIDDLE YANGTZE RIVER北大核心CSCD

To better understand zooplankton distribution and its relationship with the physical-chemical factors in middle Yangtze River, we collected 20 zooplankton samples from segments at Yichang, Jingzhou, Yueyang, Wuhan and Hukou in October, 2016. A total of 23 species that belong to 13 families and 14 genera were identified, among which 16 species belong to Rotifera, 4 to Copepoda and 3 to Cladocera. Among the five segments, the highest number of zooplankton species was detected at Hukou (9 species), while the lowest was at Yueyang (5 species). The average density at Wuhan (10.94±5.81) ind./L was higher than that at Hukou and the other segments. Rotifers (3.41±0.21) ind./L were dominant in the zooplanktonic community, and Keratella valga, Synchacta atylata and Keratella cochlearis were the dominant species. The average density of copepods (mainly nauplius) was (0.75±0.07) ind./L. Cladocera had the lowest average density. Similarly, the zooplankton biomass at Wuhan was also higher than that at Hukou and the other three segments. Comparing with studies at other segments of Yangtze River, we detected lower zooplankton diversity in our investigation. Spearman correlations indicated that the biomass and diversity of zooplankton were significantly and positively correlated (P<0.05) to chlorophyll a. © 2019, Institute of Hydrobiology, Chinese Academy of Sciences. All rights reserved.     

Genome-Wide Gene Expression Profiles of Orange and White Leafy Head Chinese Cabbage (Brassica rapa L. ssp. pekinensis) during the Summer Production Season

Russian Journal of Plant Physiology - The orange color of the inner leaves of Chinese cabbage (Brassica rapa L. ssp. pekinensis) is attributed to the high content of carotenoids, which is...     

Role of Chitosan in the Regulation of the Growth,Antioxidant System and Photosynthetic Characteristics of Maize Seedlings under Cadmium Stress

Russian Journal of Plant Physiology - Cadmium (Cd) pollution was becoming more and more serious; there is an urgent need for an effective solution to inhibit the harm of cadmium stress. Chitosan...     

Identification of Salt Stress Response Genes in Rosa chinensis Leaves by Comparative RNA-seq Analysis of Transcriptome Dynamics

Russian Journal of Plant Physiology - Rosa chinensis Jacq., originating from China, occupied a pivotal position in the floral industry all over the world. Drought and soil salinization is a major...