Overexpression of the tonoplast aquaporin AtTIP5;1 conferred tolerance to boron toxicity in Arabidopsis

Boron （B） toxicity to plants is responsible for low crop productivity in many regions of the world. Here we report a novel and effective means to alleviate the B toxicity to plants under high B circumstance. Functional characterization of AtTIP5;1, an aquaporin gene, re- vealed that overexpression ofAtTIP5;1 （OxAtT1P5;1） in Arabidopsis significantly increased its tolerance to high B toxicity. Compared to wild-type plants, OxAtTIP5;1 plants exhibited longer hypocotyls, accelerated development, increased silique production under high B treatments. GUS staining and quantitative RT-PCR （qRT-PCR） results demonstrated that the expression of AtTIP5;1 was induced by high B concentration treatment. Subcellular localization analysis revealed that the AtTIP5;1-GFP fusion protein was localized on the tonoplast membrane, which was consistent with the prediction based on bioinformatics. Taken together, our results suggest that AtTIP5; 1 is in- volved in B transport pathway possibly via vacuolar compartmentation for B, and that overexpression of AtTIP5;1 in plants may provide an effective way to overcome the problem resulting from high B concentration toxicity.

EFFECTS OF A TOXICANT ON A SINGLE-SPECIES POPULATION WITH PARTIAL POLLUTION TOLERANCE IN A POLLUTED ENVIRONMENT

We study a model for the long-term behavior of a single-species population with some degree of pollution tolerance in a polluted environment. The model consists of three ordinary differential equations： one for the population density, one for the amount of toxicant inside the living organisms, and one for the amount of toxicant in the environment. We derive sufficient conditions for the persistence and the extinction of the population depending on the exogenous input rate of the toxicant into the environment and the level of pollution tolerance of the organisms. Numerical simulations are carried out to illustrate our main results.

Vigna radiata var. GM4 Plant Growth Enhancement and Root Colonization by a Multi-Metal-Resistant Plant Growth-Promoting Bacterium Enterobacter sp. C1D in Cr(VI)-Amended Soils

Contamination of agricultural soils by heavy metals has become a major concern due to their toxic effects on plant growth,symbiosis and consequently the yields of crops. In the present study, to enhance plant growth in Cr（VI）-amended soils, novel metalresistant plant growth-promoting bacteria（PGPB） were isolated from a soil contaminated with industrial waste effluent. One of the bacterial isolates, identified as Enterobacter sp. C1 D by 16 S r RNA gene sequencing, was found to be multi-metal resistant in nature with excellent plant growth-promoting（PGP） traits. Mung bean（Vigna radiata var. GM4） inoculation with Enterobacter sp.C1 D significantly（P ＆lt; 0.01） increased root and shoot length, shoot and root weight, and chlorophyll content in a range of Cr（VI）treatments. Plant tolerance towards Cr（VI） measured as effective concentration showed higher values with Enterobacter sp. C1 Dtreated plants compared to un-inoculated plants. Root colonization study was also carried out using green fluorescence protein-labeled Enterobacter sp. C1 D under a hydroponic system. Confocal laser scanning microscopy of the plant roots showed heavy bacterial loads on the surface of the plant root specifically at the root tip and the point of root hair/lateral root formation. The results of PGP traits showed that elevated indole acetic acid levels and 1-aminocyclopropane-1-carboxylate deaminase activity enabled Enterobacter sp. C1 D to enhance V. radiata growth in Cr（VI）-amended soils, whereby it significantly increased plant tolerance towards elevated Cr（VI） concentrations.