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Mild zinc (Zn) pre-exposure can promote Zn resistance of organism, but the underlying molecular mechanisms are largely unknown. Two experiments were performed using zebrafish ZF4 cells, including short-term and long-term Zn pre-exposure experiments. In the short-term test, the cells were pre-exposed to 100 µM Zn for 24 h, transferred into fresh medium with 4.4 µM Zn for 24 h, and then re-exposed to 250 µM Zn. In the long-term test, the cells were pre-exposed to 100 µM Zn intermittently for 10 passages (3 days per passage), transferred into fresh medium with 4.4 µM Zn for 5 passages, and then re-exposed to 250 µM Zn. Both pretreatments resulted in higher resistance to 250 µM Zn. Exposure to 250 µM Zn caused a more than 2-fold increase in Zn content without Zn pretreatment but did not affect Zn content in the Zn pretreated cells. The Zn pretreated cells had low methylation levels of the metal-response element (MRE) at locus -87 in the promoter of mt2 (metallothionein 2). The up-regulated mRNA expression of Zn-regulatory genes (mtf-1, mt2, slc30a1a, slc30a4, slc30a5, slc30a6 and slc30a7) in the long-term Zn pretreated cells and mt2, slc30a4, slc30a6 and slc30a7 in the short-term Zn pretreated cells were observed. Exposure to 250 µM Zn in combination with the Zn pretreatments up-regulated mRNA expression of these genes and reduced methylation levels of the MRE compared with 250 µM Zn alone and the control. Taken together, the data suggested that demethylation of MRE in the promoter of mt2 and transcriptional induction of mt2 and Zn exporter genes offered Zn resistance in fish ZF4 cells. The traditional toxicological evaluation based on continuous exposure may overestimate the risk of fluctuating concentrations of Zn in the environment.

Made available in DSpace on 2018-12-11T16:40:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-01-01. Added 1 bitstream(s) on 2019-10-09T18:28:28Z : No. of bitstreams: 1 S1984-70332015000300132.pdf: 575410 bytes, checksum: 6d2a79208f133b9c3cd0f28862c2953d (MD5) Soybean stem necrosis is caused by Cowpea mild mottle virus (CPMMV) and it has been recognized as an emerging and economically important disease in Brazil. No resistant, but only tolerant cultivars have been identified so far, and their genetic control is still unknown. To investigate the inheritance of soybean tolerance to CPMMV, two crosses between tolerant cultivars (BRS 133 x BRSMT Pintado), and between a susceptible (CD 206) and a tolerant cultivar (BRSMT Pintado) were carried out to obtain F2 and F2:3 generations. Quantitative and qualitative analyses applied to the data from greenhouse evaluations showed that there are at least two distinct major genes determining tolerance to CPMMV, one in the soybean cultivar BRS 133 and another in the cultivar BRSMT Pintado, with predominance of additive genetic effects and heritability levels that allow for efficient selection based on early generation means. Embrapa Soja, Rodovia Carlos João Strass, s/n, acesso Orlando Amaral, CP 231, Distrito de Warta Universidade Estadual Paulista (UNESP), Campus de Botucatu, CP 237 Universidade de São Paulo Escola Superior de Agricultura Luiz de Queiroz, Agronomia, CP 9 Universidade Estadual Paulista (UNESP), Campus de Botucatu, CP 237

Soybean stem necrosis is caused by Cowpea mild mottle virus (CPMMV) and it has been recognized as an emerging and economically important disease in Brazil. No resistant, but only tolerant cultivars have been identified so far, and their genetic control is still unknown. To investigate the inheritance of soybean tolerance to CPMMV, two crosses between tolerant cultivars (BRS 133 x BRSMT Pintado), and between a susceptible (CD 206) and a tolerant cultivar (BRSMT Pintado) were carried out to obtain F2 and F2:3generations. Quantitative and qualitative analyses applied to the data from greenhouse evaluations showed that there are at least two distinct major genes determining tolerance to CPMMV, one in the soybean cultivar BRS 133 and another in the cultivar BRSMT Pintado, with predominance of additive genetic effects and heritability levels that allow for efficient selection based on early generation means. A necrose da haste em soja é causada pelo vírus Cowpea mild mottle virus (CPMMV) e é considerada uma doença emergente e economicamente importante no Brasil. Apenas cultivares tolerantes foram identificadas até o momento, e o controle genético da tolerância permanece desconhecido. Para estudar a herança da tolerância ao CPMMV foram realizados dois cruzamentos para obter as gerações F2 e F2:3, um entre duas cultivares tolerantes (BRS 133 x BRSMT Pintado) e outro entre uma cultivar suscetível (CD 206) e outra tolerante (BRSMT Pintado). Análises qualitativas e quantitativas aplicadas sobre os dados obtidos nas avaliações em casa-de-vegetação mostraram que existem pelo menos dois genes maiores distintos, um na cultivar de soja BRS 133 e outro na cultivar BRSMT Pintado, determinando a tolerância ao CPMMV. Houve predominância de efeitos genéticos aditivos e herdabilidade, que permite a seleção eficiente baseada em médias, mesmo nas primeiras gerações após o cruzamento.