Isolation and Physiological Characterization of Synechococcus cedrorum 1191 Strain Tolerant to Heavy Metals and Pesticides

The toxicity of heavy metals (Hg2 + , Zn2 + ) and pesticides has been investigated by comparing the physiological properties in wild and tolerant strains of Synechococcus cedrorum 1191. The differential pattern of growth, absorption spectra of pigments and nutrient uptake was observed in tolerant strain.

G-protein β subunit AGB1 positively regulates salt stress tolerance in Arabidopsis

The heterotrimeric GTP-binding proteins（G-proteins） in eukaryotes consisted of α, β and γ subunits and are important in molecular signaling by interacting with G-protein-coupled receptors（GPCR）, on which to transduce signaling into the cytoplast through appropriate downstream effectors. However, downstream effectors regulated by the G-proteins in plants are currently not well defined. In this study, the transcripts of AGB1, a G protein β subunit gene in Arabidopsis were found to be down-regulated by cold and heat, but up-regulated by high salt stress treatment. AGB1 mutant（agb1-2） was more sensitive to high salt stress than wild-type（WT）. Compared with WT, the cotyledon greening rates, fresh weight, root length, seedling germination rates and survival rates decreased more rapidly in agb1-2 along with increasing concentrations of Na Cl in normal（MS） medium. Physiological characteristic analysis showed that compared to WT, the contents of chlorophyll, relative proline accumulation and peroxidase（POD） were reduced, whereas the malonaldehyde（MDA） content and concentration ratio of Na＋/K＋ were increased in agb1-2 under salt stress condition. Further studies on the expression of several stress inducible genes associated with above physiological processes were investigated, and the results revealed that the expressions of genes related to proline biosynthesis, oxidative stress response, Na＋ homeostasis, stress- and ABAresponses were lower in agb1-2 than in WT, suggesting that those genes are possible downstream genes of AGB1 and that their changed expression plays an important role in determining phenotypic and physiologic traits in agb1-2. Taken together, these findings indicate that AGB1 positively regulates salt tolerance in Arabidopsis through its modulation of genes transcription related to proline biosynthesis, oxidative stress, ion homeostasis, stress- and ABA-responses.

Landscape effects on the thermotolerance of carabid beetles and the role of behavioral thermoregulation

Physiological thermotolerance and behavioral thermoregulation are central to seasonal cold adaptation in ectothermic organisms.For species with enhanced mobility,behavioral responses may be of greater importance in the cold stress response.Employing the carabid beetles as a study organism,the current study compared physiological thermotolerance and behavioral thermoregulation in carabid species inhabiting cereal fields in different landscape contexts,from fine grain heterogeneous“complex”landscapes to homogenous“simple”landscapes.Physiological thermotolerance was determined via measurement of the CTmin and chill coma temperature.Behavioral responses to cold temperature exposure were determined employing a purpose built arena,and thoracic temperature measured to estimate the efficacy of the behavior as a form of behavioral thermoregulation.Results revealed an influence of landscape composition on the cold tolerance of carabid beetles,although species differed in their sensitivity to landscape intensification.A reduced effect of landscape on the thermotolerance of larger carabid beetles was observed,thought to be the consequence of greater mobility preventing local acclimation to microclimatic variation along the landscape intensification gradient.Investigation into behavioral thermoregulation of the 3 largest species revealed burrowing behavior to be the main behavioral response to cold stress,acting to significantly raise carabid body temperature.This finding highlights the importance of behavioral thermoregulation as a strategy to evade cold stress.The use of behavioral thermoregulation may negate the need to invest in physiological thermotolerance,further offering explanation for the lack of landscape effect on the physiological thermotolerance of larger carabids.