Thermal thresholds as predictors of seed dormancy release and germination timing: altitude-related risks from climate warming for the wild grapevine Vitis vinifera subsp. sylvestris

Background and Aims

The importance of thermal thresholds for predicting seed dormancy release and germination timing under the present climate conditions and simulated climate change scenarios was investigated. In particular, Vitis vinifera subsp. sylvestris was investigated in four Sardinian populations over the full altitudinal range of the species (from approx. 100 to 800 m a.s.l).

Methods

Dried and fresh seeds from each population were incubated in the light at a range of temperatures (10–25 and 25/10 °C), without any pre-treatment and after a warm (3 months at 25 °C) or a cold (3 months at 5 °C) stratification. A thermal time approach was then applied to the germination results for dried seeds and the seed responses were modelled according to the present climate conditions and two simulated scenarios of the Intergovernmental Panel on Climate Change (IPCC): B1 (+1·8 °C) and A2 (+3·4 °C).

Key Results

Cold stratification released physiological dormancy, while very few seeds germinated without treatments or after warm stratification. Fresh, cold-stratified seeds germinated significantly better (>80 %) at temperatures ≥20 °C than at lower temperatures. A base temperature for germination (T_b) of 9·0–11·3 °C and a thermal time requirement for 50 % of germination (θ₅₀) ranging from 33·6 °Cd to 68·6 °Cd were identified for non-dormant cold-stratified seeds, depending on the populations. This complex combination of thermal requirements for dormancy release and germination allowed prediction of field emergence from March to May under the present climatic conditions for the investigated populations.

Conclusions

The thermal thresholds for seed germination identified in this study (T_b and θ₅₀) explained the differences in seed germination detected among populations. Under the two simulated IPCC scenarios, an altitude-related risk from climate warming is identified, with lowland populations being more threatened due to a compromised seed dormancy release and a narrowed seed germination window.     

Seed germination responses to varying environmental conditions and provenances in Crucianella maritima L., a threatened coastal species

Seed germination (effects of light, temperature, NaCl and KNO₃) of the coastal endangered species Crucianella maritima was investigated by testing seeds from three different populations. Data were analyzed by means of Generalized Linear Mixed Model (GLMM). The principal results showed that germination of C. maritima seeds was characterized by photoinhibition, absence of primary dormancy and salt-induced secondary dormancy, with no need for high nutrient availability (KNO₃). Intraspecific differences in germination pattern emerged, apparently due to a different seed mass. These results show important germination traits of C. maritima which should be taken into account in possible reintroduction attempts aimed at restoring threatened populations of this species.     

Light,temperature, dry after‐ripening and salt stress effects on seed germination of Phleum sardoum (Hackel) Hackel

Phleum sardoum is an endemic psammophilous species of Sardinia, growing exclusively on coastal sandy dunes. The effect of glumes on seed germination, germination requirements at constant (5–25°C) and alternating (25/10°C) temperatures, both in the light (12/12 h) and in the dark were evaluated, as well as the effect of a dry after‐ripening period (90 days at 25°C), the salt stress effect (0–600 mmol NaCl) and its recovery on seed germination. The presence of glumes reduced final germination percentages. For fresh naked seeds, high germination percentages were observed at 10°C. Dry after‐ripening increased germination rate at low temperatures, but did not affect final germination percentages. NaCl determined a secondary salt‐induced dormancy which recovery interrupted only partially. Our results highlighted that this species has its optimum of germination during autumn–winter when, under a Mediterranean climate, water availability is highest and soil salinity levels are minimal.     

Backbone-free transformation of barrel medic (Medicago truncatula) with a Medicago-derived transfer DNA

In the present work, Agrobacterium tumefaciens-mediated genetic transformation of the model legume Medicago truncatula Gaertn. (barrel medic) was carried out using the pSIM843 vector that contains a Medicago-derived transfer DNA, delineated by a 25-bp sequence homologous to bacterial T-DNA borders. The transfer DNA contains an expression cassette for the nptII (neomycin phosphotransferase) gene and is flanked by an expression cassette for the backbone integration marker gene ipt (isopentenyl transferase). Our results demonstrate that the Medicago-derived RB-like elements efficiently support DNA mobilization from A. tumefaciens to M. truncatula. Kanamycin-resistant shoots with normal phenotype and ipt-shooty lines were recovered at a frequency of 11.7 and 7.8%, respectively. Polymerase chain reaction (PCR) analyses demonstrated that 44.4% of the independent transgenic lines were backbone-free and evidenced the occurrence of backbone-transfer events.     

Geographic isolation affects inter- and intra-specific seed variability in the Astragalus tragacantha complex,as assessed by morpho-colorimetric analysis

The effect of geographical isolation on the inter- and intra-specific seed variability of the Astragalus tragacantha complex was investigated by using a computer-aided imaging system. In particular, seed morphometric and colorimetric features of Astragalus balearicus, A. tegulensis, A. terraccianoi, A. thermensis and A. tragacantha were measured and the data were used to discriminate among regions of provenance, taxa and populations. Discriminant analysis of the data supports the accepted taxonomy of the group and the hypothesis that interspecific differentiation resulted from geographical isolation. The results also showed a positive correlation between the wideness of species’ distribution and the levels of seed intra-specific variability.     

Altered Glucose Homeostasis Is Associated with Increased Serum Apelin Levels in Type 2 Diabetes Mellitus

Background

Apelin is an adipokine that plays a role in the regulation of glucose homeostasis and in obesity. The relationship between apelin serum concentration and dysmetabolic conditions such as type 2 diabetes (T2D) is still controversial. Aims of our study are: 1) determine the circulating levels of apelin in a large cohort of Italian subjects with T2D, T1D and in non-diabetic controls; 2) identify putative metabolic determinants of modified apelin concentrations, in order to search possible mechanism of apelin control; 3) investigate changes in apelin levels in response to sharp modifications of glucose/insulin metabolism in T2D obese subjects before and 3 days after bariatric surgery.

Methods

We recruited 369 subjects, 119 with T2D, 113 with T1D and 137 non-diabetic controls. All subjects underwent a complete clinical examination, including anthropometric and laboratory measurements. Serum apelin levels were determined by EIA (immunoenzyme assay).

Results

Patients with T2D had significantly higher serum apelin levels compared to controls (1.23±1.1 ng/mL vs 0.91±0.7 ng/mL, P<0.001) and to T1D subjects (0.73±0.39 ng/mL, P<0.001). Controls and T1D subjects did not differ significantly in apelin levels. Apelin concentrations were directly associated with fasting blood glucose (FBG), body mass index (BMI), basal Disposition Index (DI-0), age, and diagnosis of T2D at bivariate correlation analysis. Multiple regression analysis confirmed that diagnosis of T2D, basal DI-0 and FBG were all determinants of serum apelin levels independently from age and BMI. Bariatric surgery performed in a subgroup of obese diabetic subjects (n = 12) resulted in a significant reduction of apelin concentrations compared to baseline levels (P = 0.01).

Conclusions

Our study demonstrates that T2D, but not T1D, is associated with increased serum apelin levels compared to non-diabetic subjects. This association is dependent on impaired glucose homeostasis, and disappears after bariatric surgery, providing further evidence regarding the relationship between apelin and the regulation of glucose metabolism.     

An Italian functional genomic resource for <Emphasis Type="Italic">Medicago truncatula</Emphasis>

Background

Medicago truncatula is a model species for legumes. Its functional genomics have been considerably boosted in recent years due to initiatives based both in Europe and US. Collections of mutants are becoming increasingly available and this will help unravel the genetic control of important traits for many species of legumes.

Findings

Our report is on the production of three complementary mutant collections of the model species Medicago truncatula produced in Italy in the frame of a national genomic initiative. Well established strategies were used: Tnt1 mutagenesis, TILLING and activation tagging. Both forward and reverse genetics screenings proved the efficiency of the mutagenesis approaches adopted, enabling the isolation of interesting mutants which are in course of characterization. We anticipate that the reported collections will be complementary to the recently established functional genomics tools developed for Medicago truncatula both in Europe and in the United States.

     

Delay of leaf senescence in <Emphasis Type="Italic">Medicago sativa</Emphasis> transformed with the <Emphasis Type="Italic">ipt</Emphasis> gene controlled by the senescence-specific promoter SAG12

We report the successfull delay of leaf senescence in Medicago sativa. A highly regenerable clone of alfalfa was transformed with the construct SAG12-IPT, an approach that has already proved efficient in other crops. Several independent transformants were obtained as determined by Southern analysis and all the transformants expressed the transgene as measured by RT-PCR. In vitro and in vivo analyses showed that SAG12-IPT plants exhibited a stay-green phenotype that has the potential to greatly improve the quantity and quality of alfalfa forage.