Expression of two heterologous promoters, Agrobacterium rhizogenes rolC and cauliflower mosaic virus 35S, in the stem of transgenic hybrid aspen plants during the annual cycle of growth and dormancy

We monitored, for the first time, the activity of two model heterologous promoters, the Agrobacterium rhizogenes rolC and the cauliflower mosaic virus (CaMV) 35S, throughout the annual cycle of growth and dormancy in a perennial species, hybrid aspen. Each promoter was fused to the uidA -glucuronidase (GUS) reporter gene and the constructs were introduced into the hybrid aspen genome by Agrobacterium-mediated transformation. Both wildtype and transgenic plants were cultivated under different regimes of photoperiod and temperature to induce passage through one growth-dormancy-reactivation cycle, and at intervals GUS staining was assessed in stem sections. In rolC::uidA transformants, GUS activity in rapidly growing current-year shoots was not only tissue-specific, being localized to the phloem, but also cell-specific at the shoot base, where it was present only in the companion cells. However, during the onset of dormancy induced by short photoperiod, GUS activity shifted laterally from the phloem to include the cortex and pith. After subsequent exposure to chilling temperatures to induce the transition between the dormancy stages of rest and quiescence, GUS activity almost disappeared from all stem tissues, but regained its original phloem specificity and intensity after the shoots were reactivated by exposing them to long photoperiod and high temperatures. In contrast, GUS activity in the stem of 35S::uidA transformants was strong in all tissues except for the vascular cambium and xylem, and did not vary in intensity during the growth-dormancy-reactivation cycle. The lateral shift and increased intensity of GUS activity in the stem of rolC::uidA transformants during dormancy induction was shown to be associated with the accumulation of starch, and to be mimicked by incubating stem sections in sucrose, as well as glucose and fructose, but not sorbitol, prior to the GUS assay. Our results demonstrate that the activities of the rolC and 35S promoters varied in very different, unpredictable ways during the annual cycle of growth and dormancy in a perennial species, and indicate that the spatial and temporal variation in rolC promoter activity that we observed in the stem of transgenic hybrid aspen plants is attributable to cellular and seasonal changes in sucrose content.     

Distribution of PACAP (pituitary adenylate cyclase-activating polypeptide)-like and helospectin-like peptides in the teleost gut

Pituitary adenylate cyclase-activating polypeptide (PACAP) and helospectin are two vasoactive intestinal polypeptide (VIP)-related neuropeptides that have recently been demonstrated in the mammalian gut; the aim of this study was to reveal their occurrence and localisation in the gastrointestinal tract, swimbladder, urinary bladder and the vagal innervation of the gut of teleosts, using immunohistochemical methods on whole-mounts and sections of these tissues from the Atlantic cod, Gadus morhua and the rainbow trout, Oncorhynchus mykiss. Both PACAP-like and helospectin-like peptides were present in the gut wall of the two species. Immunoreactive nerve fibres were found in all layers but were most frequent in the myenteric plexus and along the circular muscle fibres. Immunoreactivity was also demonstrated in nerves innervating the swimbladder wall, the urinary bladder and blood vessels to the gut. Immunoreactive nerve cell bodies were found in the myenteric plexus of the gut and in the muscularis mucosae of the swimbladder. In the vagus nerve, non-immunoreactive nerve cells were surrounded by PACAP-immunoreactive fibres. Double staining revealed the coexistence of PACAP-like and helospectin-like peptides with VIP in all visualized nerve fibres and in some endocrine cells. It is concluded that PACAP-like and helospectin-like peptides coexist with VIP in nerves innervating the gut of two teleost species. The distribution suggests that both PACAP and helospectin, like VIP, are involved in the control of gut motility and secretion.     

Hormonal Characterization of Transgenic Tobacco Plants Expressing the rolC Gene of Agrobacterium rhizogenes TL-DNA

Transgenic tobacco (Nicotiana tabacum L. cv Wisconsin 38) plants expressing the Agrobacterium rhizogenes rolC gene under the control of the cauliflower mosaic virus 35S RNA promoter were constructed. These plants displayed several morphological alterations reminiscent of changes in indole-3-acetic acid (IAA), cytokinin, and gibberellin (GA) content. However, investigations showed that neither the IAA pool size nor its rate of turnover were altered significantly in the rolC plants. The biggest difference between rolC and wild-type plants was in the concentrations of the cytokinin, isopentenyladenosine (iPA) and the gibberellin GA19. Radio-immunoassay and liquid chromatography-mass spectrometry measurements revealed a drastic reduction in rolC plants of iPA as well as in several other cytokinins tested, suggesting a possible reduction in the synthesis rate of cytokinins. Furthermore, gas chromatography-mass spectrometry quantifications of GA19 showed a 5- to 6-fold increase in rolC plants compared with wild-type plants, indicating a reduced activity of the GA19 oxidase, a proposed regulatory step in the gibberellin biosynthesis. Thus, we conclude that RolC activity in transgenic plants leads to major alterations in the metabolism of cytokinins and gibberellins.     

Significant increase in natural disturbance impacts on European forests since 1950

Over the last decades, the natural disturbance is increasingly putting pressure on European forests. Shifts in disturbance regimes may compromise forest functioning and the continuous provisioning of ecosystem services to society, including their climate change mitigation potential. Although forests are central to many European policies, we lack the long-term empirical data needed for thoroughly understanding disturbance dynamics, modeling them, and developing adaptive management strategies. Here, we present a unique database of >170,000 records of ground-based natural disturbance observations in European forests from 1950 to 2019. Reported data confirm a significant increase in forest disturbance in 34 European countries, causing on an average of 43.8 million m³ of disturbed timber volume per year over the 70-year study period. This value is likely a conservative estimate due to under-reporting, especially of small-scale disturbances. We used machine learning techniques for assessing the magnitude of unreported disturbances, which are estimated to be between 8.6 and 18.3 million m³/year. In the last 20 years, disturbances on average accounted for 16% of the mean annual harvest in Europe. Wind was the most important disturbance agent over the study period (46% of total damage), followed by fire (24%) and bark beetles (17%). Bark beetle disturbance doubled its share of the total damage in the last 20 years. Forest disturbances can profoundly impact ecosystem services (e.g., climate change mitigation), affect regional forest resource provisioning and consequently disrupt long-term management planning objectives and timber markets. We conclude that adaptation to changing disturbance regimes must be placed at the core of the European forest management and policy debate. Furthermore, a coherent and homogeneous monitoring system of natural disturbances is urgently needed in Europe, to better observe and respond to the ongoing changes in forest disturbance regimes.     

Morphological differentiation in Carduelis finches: Adaptive vs. constraint models

In this study we show that morphological diversification in the avian genus Carduelis (Carduelinae) has to a large extent been conservative. Using multivariate methods, we found only minor deviations from the common (ancestral) body-plan. In particular, variation in bill morphology was found to be more conservative than variation in other parts of the body. We argue that constraint models of population differentiation can successfully account for the variation in bill morphology in this genus, but are less successful in accounting for variation in other traits. This can be interpreted as a result of long-term overall stabilizing selection for a certain bill morphology which is related to the way the birds open seeds. A trait combination that is adaptive on the evolutionary time scale may thus act as a constraint on changes in bill morphology on the microevolutionary scale. We conclude that the most parsimonious explanation for low divergence in bill morphology in this genus is that all species have retained the ancestral bill morphology. This may mean that each species chooses its environment rather than being moulded by it. This argument seems to apply to bill morphology, but other traits studied in this genus appear to have evolved in a less constrained fashion. A new index of morphometric integration is introduced to describe covariance structures.     

A trait-based approach to assess niche overlap and functional distinctiveness between non-indigenous and native species

Our understanding of the community assembly processes acting on non-indigenous species (NIS), as well as the relationship with native species is limited, especially in marine ecosystems. To overcome this knowledge gap we here develop a trait-based approach based on the functional distinctiveness metric to assess niche overlap between NIS and native species, using high-resolution data on benthic invertebrate communities in the Baltic Sea. Our results show that NIS retain a certain degree of similarity with native species, but display one or a few singular unique traits (e.g., bioturbation ability). Furthermore, we demonstrate that community assembly processes, including both environmental filtering and limiting similarity affect NIS establishment, but that their effects may be highly context dependent, as illustrated by pronounced spatial patterns in distinctiveness. Finally, our trait-based approach provides a generic framework applicable to other areas and organisms, to better understand and address biological invasions.     

Factors controlling the population dynamics of the clonal helophyte Ranunculus lingua

Abstract. Two marginal and two central populations of the pseudo-annual aquatic plant Ranunculus lingua were studied over four years. The main purpose was to quantify potentially influential abiotic and biotic factors and to derive predictions about life-history differences between the populations. Variation in abundance and height of R. lingua ramets at different depths were related to water-level fluctuations, to abundance of other helophyes (emergent macrophytes), and to the occurrence of invertebrate grazing and fungal pathogens. Clear differences between marginal and central populations were shown in the depth distribution of ramet numbers and ramet heights, as well as in the dynamic patterns, where marginal populations had a higher flux of ramets. These patterns and regression analyses indicated that abiotic factors have a greater influence in marginal populations, whereas biotic factors are more important in central populations. It is suggested that marginal habitats for R. lingua would favour life-histories with a high reproductive capacity, whereas a large size of ramet would be the most important life-history feature in central habitats. This was supported by the fact that ramets in marginal populations, in spite of their smaller size, produced higher number of rhizomes than ramets in central populations. Variation in regional abundance was finally related to differences in demographic processes and dispersal potential between the populations.     

A new species of Croton (Euphorbiaceae) from Somalia

Croton crispatus , sp. nov., from Acacia-Commiphora bushland on sand in central Somalia, is described and illustrated.     

Acacia ochracea (Leguminosae-Mimosoideae), a new species from Somalia

Acacia ochracea , a new species in the A. Senegal complex, is described and illustrated. It is a common and conspicuous tree over large areas in the western Bay Region and in the Gedo Region in SW Somalia.     

New or noteworthy species of Leguminosae in NE tropical Africa

The following new species are described: Chamaecrista dunensis (Somalia), Acacia densispina (Somalia), A. flagellaris (Somalia), Tephrosia karkarensis (Somalia), T. scopulata (Somalia), Indigofera ancistrocarpa (Kenya), I. curvirostrata (Ethiopia), I. hiranensis (Somalia), I. karinensis (Somalia), I. kucharii (Somalia), I. nugalensis (Somalia), I. pellucida (Kenya, Somalia), I. sabulosa (Ethiopia, Somalia), I. sessilis (Somalia), I. ienuirostris (Somalia), Rhynchosia megalocalyx (Somalia), Crotalaria allophylla (Somalia), C. intricata (Somalia), C. warfae (Somalia), and Coronilla somalensis (Somalia). 2n = 22 is reported in Tephrosia karkarensis. Cassia somalensis, Acacia puccioniana, Sophora somalensis , and Crotalaria sennii are reduced to synonyms of respectively Senna hookeriana, Dichrostachys kirkii, Millettia usaramensis and Crotalaria boranica subsp. trichocarpa . Thirty-seven taxa are reported from Somalia for the first time, including Ptycholobium biflorum , known previously only from Southern Africa. Crotalaria pieropoda , known previously only from Socotra, is reported from Somalia and Oman. Neptunia oleracea and Vatovaea pseudolablab are new generic records for respectively Ethiopia and Oman. The fruits of Indigofera boranica are described. Vigna somaliensis and an allied species are discussed. Rhynchosia gansole is lectotypified and its flowers and fruits are described.