Systemic H2O2 signaling mediates epigallocatechin-3-gallate-induced cadmium tolerance in tomato.

Toxic heavy metal cadmium (Cd) reduces crop yield and threatens human health via the food chain. The bioactive flavonoid 'Epigallocatechin-3-gallate' (EGCG) affects plant stress response; however, the function of EGCG in Cd tolerance and the molecular pathways remain largely unknown. Here, we revealed that root application of EGCG alleviated Cd stress in tomato plants. While Cd stress decreased Fv/Fm, ФPSII, photosynthetic rate, root growth, root vitality and biomass accumulation by increasing reactive oxygen species (ROS) accumulation and lipid peroxidation, exogenous EGCG minimized excessive ROS accumulation and oxidative stress by promoting the activity of antioxidant enzymes and redox poise in roots and leaves. Moreover, EGCG induced the transcript of RESPIRATORY BURST OXIDASE HOMOLOG1 (RBOH1) and decreased Cd content and photoinhibition in leaves. Interestingly, similar to EGCG, exogenous H2O2 application also enhanced Cd tolerance; however, the application of an NADPH oxidase inhibitor, diphenyleneiodonium (DPI), aggravated Cd phytotoxicity and attenuated the beneficial effects of EGCG on plant tolerance to Cd stress, suggesting that root applied EGCG-induced expression of RBOH1 and associated H2O2 signaling mediate the EGCG-induced enhanced Cd tolerance. This work elucidates a fundamental mechanism behind EGCG-mediated Cd tolerance and contributes to our existing knowledge of stress resistance properties of EGCG in plants.

[A diachronic study on resettlers' perceptions toward ecological relocation in world heritage site: A case study of Wulingyuan Scenic Area, China]. / é—äº§æ— æ¸¸åœ°å± æ°‘å¯¹ç”Ÿæ€ç§»æ°‘å½±å“æ„ŸçŸ¥çš„åŽ†æ—¶æ€§ç ”ç©¶­­ä»¥æ­¦é™µæºé£Žæ™¯åèƒœåŒºä¸ºä¾‹.

Perceptions of residents in ecological resettlement area are important for evaluating the implementation effect of ecological relocation and sustainable development of world heritage site. With the residents from three different resettlement communities in Wulingyuan Scenic Area as the research object, we carried out a diachronic study on changes of the resettlers' perceptions of ecological relocation at different times and the main driving factors based on systematic survey data in 2010 and 2016. The results showed that in the year 2010 and 2016, resettlers reacted negatively to the indicators such as "enhancement of employment opportunity", "improvement of education and training opportunity", "enhanced environment in scenic area", "recognizing the identity change 'from rural to non-rural' after relocation". They favored the indicators such as "undermining traditional value", "lack of supervision during the implementation of policies". In 2016, resettlers of different gender, age and average monthly income had substantial different opinions on the economic and psychological impacts of ecological relocation. Education and income level had great impacts on their opinions of ecological relocation policies. Resettlers relocated by the way of investment for developing perceived were more sensitive to the economic impacts. Economic and policy impacts became the dominant driving factors for their general perception of ecological relocation. They pay more attention to employment, children's education opportunity as well as social security system for relocation.

[Activation tagging and its application in plant functional genomics research].

It is a practical strategy to screen for mutants in the research of plant functional genomics. Comparing with classical T-DNA knock-out mutagenesis technology by the loss-of-function mutation, the activation T-DNA tagging technique based on the gain-of-function mutation has its own particular advantages, mainly characterized by producing dominant mutants of genes with functional redundancy and easily cloning of the genes. First, the basic principle of activation tagging, and the progress of its application in the research on plant functional genomics was reviewed, especially in Arabidopsis and rice. The recent research progress in the mechanism of plant biotic and abiotic stress tolerance and of plant development unraveled by the method of activation tagging was then addressed. Finally, the limitation and prospects of this technique were discussed.

[Construction of an activation tagging library of Arabidopsis and cloning for mutant genes].

Activation tagging is an important strategy in plant genomics by generating gain-of-function mutants. In this work, a library of Arabidopsis mutants was constructed by in planta transformation mediated by Agrobacterium tumefaciens containing an activation tagging vector pSKI015 with herbicide Basta as a selection marker (Fig. 1). Among 20000 independent transformants, 38 lines, i.e. about 0.2% of T(1) progeny, show visible morphological phenotypic variations (Fig. 2). Results of Southern blot analysis revealed that most of the transformants have more than three copies of T-DNA insertion (Fig. 3). Plasmid rescue and TAIL-PCR were used to recover the flanking genomic sequences of mutated target genes as the first step towards mutant gene cloning (Fig. 4, 5).

[sdt1, a novel Arabidopsis mutant tolerant to drought and high-salinity stresses].

Among the 20000 independent Arabidopsis activation tagging lines, we screened a novel mutant with high-salinity and drought tolerance, namely sdt1 (high-salinity and drought tolerant 1). sdt1 kept normal growth under drought stress by consecutively withholding water for 26d, while all the wild type wilted to death. Furthermore, the same result was repeated under high-salinity stress when sdtl and wild type were treated with 150 mmol/L NaCl. Seeds germination test on the medium indicated that the response of sdt1 to endogenous or exogenous ABA was reduced as compared with wild type. Under drought stress conditions the rates of water loss of sdt1 rosette leaves were significantly lower than that of wild type. Southern hybridization of sdt1 and the result of high-salinity tolerance genetic analysis showed that two copies of T-DNA were inserted into the two linking sites by shoulder to shoulder.