Aphids (Hemiptera: Aphididae) are phytophagous insects that are important agricultural pests. The enormous negative economic impacts caused by aphids worldwide are well known, and are mostly due to their high multiplication rate and the transmission of phytopathogenic viruses. Aphid management strategies mainly involve chemical treatments which are pollutants and are increasingly inefficient, since aphids have developed multiple insecticide-resistant mechanisms. Among the most economically important species is the green peach aphid Myzus persicae Sulzer (Aphididae: Macrosiphini), which is able to colonize a wide range of host plants belonging to many different families, and transmits numerous plant viruses. Because of its large prevalence, M. persicae has been the target of massive insecticide treatments; consequently, it has evolved several insecticide-resistant mechanisms. In this work, a collection of expressed genes from M. persicae is presented in order to identify putative genes involved in xenobiotic detoxification. After cDNA cloning and sequencing, 959 expressed sequence tags (EST) were annotated. Most sequences matched known genes corresponded to metabolism proteins (26%), ribosomal proteins (23%) and structural proteins (8%). Among them, several sequences corresponded to proteins putatively involved in sensing, degradation or detoxification of plant xenobiotic products.

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Reversible in vivo cellular changes occur during desiccation and recovery: Desiccation tolerance of the resurrection filmy fern Hymenophyllum dentatum Cav.Cambios celulares reversibles observados in vivo durante la desecación y recuperación: Tolerancia a la desecación del helecho película de resurrección Hymenophyllum dentatum Cav. SORAYA ABSTRACTThe present work explores in vivo physiological, morphological and chemical features during full hydration, desiccation and rehydration of the filmy fern Hymenophyllum dentatum with two main objectives: 1) to get further insight about the mechanisms underlying its desiccation tolerance, and 2) to understand how this plant manages mechanical stress induced by water loss and recovery. With these purposes, physiological (relative water content and F v /F m chlorophyll fluorescence parameter), morphological (Confocal Laser Scanning Microscopy and 3D reconstruction) and chemical (FT-IR microspectroscopy) data were obtained and compared between fully hydrated, desiccated and rehydrated tissues of H. dentatum. Remarkable changes in cell architecture and chemical composition were observed in vivo in desiccated leaves. Cells were smaller, showed a collapsed general appearance, and were delimitated by apparently folded cell walls. Marked changes in chloroplasts location and decrease in the number of active chloroplasts were also evidenced. Chemical experiments showed that changes in the secondary structure of proteins and in the polysaccharide composition of the cell wall occur in desiccated cells. All changes were rapidly reversed upon rehydration. This study shows that H. dentatum presents an extreme case of desiccation tolerance, able to withdraw severe, rapid and consecutive dehydration/rehydration induced stress by the function of constitutive systems of protection and reparation, in which cell wall folding plays a relevant role as a protective system against mechanical and oxidative stress. Besides, H. dentatum is proposed as an excellent plant model for the study of dissection tolerance such as one cell layer fern, auto-fluorescence of cellular compartments, and simple long term storage under laboratory conditions, among others. KEYWORDS:Hymenophyllum, desiccation tolerance, confocal 3D microscopy, FT-IR microspectroscopy, rapid dehydration /rehydration. RESUMENEl presente trabajo muestra una exploración in vivo de los rasgos fisiológicos, morfológicos y químicos que caracterizan a los estados de hidratación completa, desecación y rehidratación del helecho película Hymenophyllum dentatum, que persigue 2 objetivos principales: 1) Adquirir conocimientos sobre los mecanismos que subyacen a la tolerancia a la desecación, y 2) entender cómo estas plantas manejan el estrés mecánico inducido por la pérdida y recuperación de agua. Con estos propósitos se obtuvo datos fisiológicos (contenido relativo de agua y parámetro de fluorescencia de clorofila Fv/Fm), ISSN 0016-5301 Gayana Bot. 73(2): [402][403][404][405][406][407][408][409][410][411][412][413] 2016 403In vivo cellular ch...

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