RESUMO
The effect of high temperature and oxidative stress on the cell viability of the yeast antagonist, Metschnikowia fructicola was determined. A mild heat shock (HS) pretreatment (30 min at 40 °C) improved the tolerance of M. fructicola to subsequent high temperature (45 °C, 20-30 min) and oxidative stress (0.4 mol L⻹ hydrogen peroxide, 20-60 min). HS-treated yeast cells showed less accumulation of reactive oxygen species (ROS) than nontreated cells in response to both stresses. Additionally, HS-treated yeast exhibited significantly greater (P<0.0001) biocontrol activity against Penicillium expansum and a significantly faster (P<0.0001) growth rate in wounds of apple fruits stored at 25 °C compared with the performance of untreated yeast cells. Transcription of a trehalose-6-phosphate synthase gene (TPS1) was upregulated in response to HS and trehalose content also increased. Results indicate that the higher levels of trehalose induced by the HS may contribute to an improvement in ROS scavenging, stress tolerance, population growth in apple wounds and biocontrol activity of M. fructicola.
Assuntos
Antibiose , Resposta ao Choque Térmico , Temperatura Alta , Metschnikowia/fisiologia , Estresse Oxidativo , Sequência de Bases , Frutas/microbiologia , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Glucosiltransferases/genética , Glucosiltransferases/metabolismo , Peróxido de Hidrogênio/farmacologia , Malus/microbiologia , Metschnikowia/genética , Viabilidade Microbiana , Dados de Sequência Molecular , Penicillium/patogenicidade , Penicillium/fisiologia , Doenças das Plantas/prevenção & controle , Espécies Reativas de Oxigênio/análise , Trealose/biossínteseRESUMO
Dehydrins are one of several proteins that have been specifically associated with qualitative and quantitative changes in cold hardiness. Recent evidence indicates that the regulation of dehydrin genes by low nonfreezing temperature (LT) and short photoperiod (SD) can be complex and deserves more detailed analysis to better understand the role of specific dehydrin genes and proteins in the response of woody plants to environmental stress. We have identified a new peach (Prunus persica (L.) Batsch) dehydrin gene (PpDhn2) and examined the responses of this gene and a previously identified dehydrin (PpDhn1) to SD, LT and water deficit. PpDhn2 was strongly induced by water deficit but not by LT or SD. It was also present in the mature embryos of peach. In contrast, PpDhn1 was induced by water deficit and LT but not by SD. We conducted an in silico analysis of the promoters of these genes and found that the promoter region of PpDhn1 contained two dehydration-responsive-elements (DRE)/C-repeats that are responsive to LT and several abscisic acid (ABA)-response elements (ABREs). In contrast, the promoter region of PpDhn2 contained no LT elements but contained several ABREs and an MYCERD1 motif. Both promoter analyses were consistent with the observed expression patterns. The discrepancy between field-collected samples and growth-chamber experiments in the expression of PpDhn1 in response to SD suggests that SD-induced expression of dehydrin genes is complex and may be the result of several interacting factors.
Assuntos
Perfilação da Expressão Gênica , Fotoperíodo , Proteínas de Plantas/genética , Prunus/genética , Sequência de Aminoácidos , Sequência de Bases , Temperatura Baixa , Desastres , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Dados de Sequência Molecular , Isoformas de Proteínas/genética , Prunus/metabolismo , Prunus/efeitos da radiação , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Alinhamento de Sequência , Temperatura , Água/metabolismoRESUMO
Recent research of the Agricultural Research Service of USDA on the use of natural products to manage pests is summarized. Studies of the use of both phytochemicals and diatomaceous earth to manage insect pests are discussed. Chemically characterized compounds, such as a saponin from pepper (Capsicum frutescens L), benzaldehyde, chitosan and 2-deoxy-D-glucose are being studied as natural fungicides. Resin glycosides for pathogen resistance in sweet potato and residues of semi-tropical leguminous plants for nematode control are also under investigation. Bioassay-guided isolation of compounds with potential use as herbicides or herbicide leads is underway at several locations. New natural phytotoxin molecular target sites (asparagine synthetase and fructose-1,6-bisphosphate aldolase) have been discovered. Weed control in sweet potato and rice by allelopathy is under investigation. Molecular approaches to enhance allelopathy in sorghum are also being undertaken. The genes for polyketide synthases involved in production of pesticidal polyketide compounds in fungi are found to provide clues for pesticide discovery. Gene expression profiles in response to fungicides and herbicides are being generated as tools to understand more fully the mode of action and to rapidly determine the molecular target site of new, natural fungicides and herbicides.
