Characterization of a family of Arabidopsis trehalose biosynthesis genes and their role in root development and stress tolerance

Sugars are the fuel of life to plants and other organisms. They are the result of the fixed energy from the sun that feeds the plant cells to sustain growth and development. Sucrose is the main sugar transported in the plant and, as such reaches the cells where it is cleaved in glucose and fructose. Many vital processes are governed by sugars, but complex networks had to evolve allowing the plant to trigger the right program depending on its energy status. Surprisingly, one sugar phosphate is emerging to connect carbon status with the growth program. That sugar is trehalose-6-phosphate, the intermediate on the trehalose metabolism pathway. This molecule is a signal of sucrose status in the cell and it is also an inhibitor of the main regulator of starvation responses in plants. The mechanism mediating trehalose-6-phosphate balancing of energy levels is waiting to be unraveled. The aim of this work was to scout into the possible role of the trehalose biosynthesis pathway in root development and stress tolerance. The focus was on the 10 active phosphatase members that convert the intermediate trehalose-6-phosphate into trehalose. By a forward genetics approach, we could identify two potential candidates important for lateral root development. Interestingly, they appear to function in an antagonistic manner in this organogenesis process and are regulated by auxin. Additionally, two other enzymes in the trehalose pathway were found to regulate abscisic acid responses. With these results, we open a big window of research searching on the molecular and hormonal components interacting with the trehalose pathway

Expansive evolution of the TREHALOSE-6-PHOSPHATE PHOSPHATASE gene family in Arabidopsis

Trehalose is a nonreducing sugar used as a reserve carbohydrate and stress protectant in a variety of organisms. While higher plants typically do not accumulate high levels of trehalose, they encode large families of putative trehalose biosynthesis genes. Trehalose biosynthesis in plants involves a two-step reaction in which trehalose-6-phosphate (T6P) is synthesized from UDPglucose and glucose-6-phosphate (catalyzed by T6P synthase [TPS]), and subsequently dephosphorylated to produce the disaccharide trehalose (catalyzed by T6P phosphatase [TPP]). In Arabidopsis (Arabidopsis thaliana), 11 genes encode proteins with both TPS- and TPP-like domains but only one of these (AtTPS1) appears to be an active (TPS) enzyme. In addition, plants contain a large family of smaller proteins with a conserved TPP domain. Here, we present an in-depth analysis of the 10 TPP genes and gene products in Arabidopsis (TPPA-TPPJ). Collinearity analysis revealed that all of these genes originate from whole-genome duplication events. Heterologous expression in yeast (Saccharomyces cerevisiae) showed that all encode active TPP enzymes with an essential role for some conserved residues in the catalytic domain. These results suggest that the TPP genes function in the regulation of T6P levels, with T6P emerging as a novel key regulator of growth and development in higher plants. Extensive gene expression analyses using a complete set of promoter-beta-glucuronidase/green fluorescent protein reporter lines further uncovered cell- and tissue-specific expression patterns, conferring spatiotemporal control of trehalose metabolism. Consistently, phenotypic characterization of knockdown and overexpression lines of a single TPP, AtTPPG, points to unique properties of individual TPPs in Arabidopsis, and underlines the intimate connection between trehalose metabolism and abscisic acid signaling

Redundant and non-redundant roles of the trehalose-6-phosphate phosphatases in leave growth, root hair specification and energy-responses in Arabidopsis

The Arabidopsis trehalose-6-phosphate phosphatase (TPP) gene family arose mainly from whole genome duplication events and consists of 10 genes (TPPA-J). All the members encode active TPP enzymes, possibly regulating the levels of trehalose-6-phosphate, an established signaling metabolite in plants. GUS activity studies revealed tissue-, cell- and stage-specific expression patterns for the different members of the TPP gene family. Here we list additional examples of the remarkable features of the TPP gene family. TPPA-J expression levels seem, in most of the cases, differently regulated in response to light, darkness and externally supplied sucrose. Disruption of the TPPB gene leads to Arabidopsis plants with larger leaves, which is the result of an increased cell number in the leaves. Arabidopsis TPPA and TPPG are preferentially expressed in atrichoblast cells. TPPA and TPPG might fulfill redundant roles during the differentiation process of root epidermal cells, since the tppa tppg double mutant displays a hairy root phenotype, while the respective single knockouts have a distribution of trichoblast and atrichoblast cells similar to the wild type. These new data portray redundant and non-redundant functions of the TPP proteins in regulatory pathways in Arabidopsis

Overexpression of the trehalase gene AtTRE1 leads to increased drought stress tolerance in Arabidopsis and is involved in abscisic acid-induced stomatal closure

Introduction of microbial trehalose biosynthesis enzymes has been reported to enhance abiotic stress resistance in plants but also resulted in undesirable traits. Here, we present an approach for engineering drought stress tolerance by modifying the endogenous trehalase activity in Arabidopsis (Arabidopsis thaliana). AtTRE1 encodes the Arabidopsis trehalase, the only enzyme known in this species to specifically hydrolyze trehalose into glucose. AtTRE1-overexpressing and Attre1 mutant lines were constructed and tested for their performance in drought stress assays. AtTRE1-overexpressing plants had decreased trehalose levels and recovered better after drought stress, whereas Attre1 mutants had elevated trehalose contents and exhibited a drought-susceptible phenotype. Leaf detachment assays showed that Attre1 mutants lose water faster than wild-type plants, whereas AtTRE1-overexpressing plants have a better water-retaining capacity. In vitro studies revealed that abscisic acid-mediated closure of stomata is impaired in Attre1 lines, whereas the AtTRE1 overexpressors are more sensitive toward abscisic acid-dependent stomatal closure. This observation is further supported by the altered leaf temperatures seen in trehalase-modified plantlets during in vivo drought stress studies. Our results show that overexpression of plant trehalase improves drought stress tolerance in Arabidopsis and that trehalase plays a role in the regulation of stomatal closure in the plant drought stress response

Perfil cognitivo y social en niños y niñas con Trastorno del Espectro Autista

El Trastorno del Espectro Autista (TEA) es una condición que se caracteriza por presentar fallas en la conducta social y comportamientos repetitivos. Su perfil neuropsicológico muestra hallazgos heterogéneos que dependen de la severidad del trastorno. El objetivo del presente trabajo es describir el funcionamiento neuropsicológico de una muestra de niños y niñas con TEA que asisten al Instituto para el Desarrollo Integral del Niño en condición de Autismo (DINA). La muestra estuvo conformada por 78 participantes, 15.4 % de género femenino y 84.6 % de género masculino, con edades entre los 6 y los 16 años. Los instrumentos utilizados fueron protocolo neuropsicológico adaptado de la ENI, prorrateo de inteligencia del WISC-IV, Test de Sally y Ann, Test de Expresiones faciales adaptado por Paul Ekman y el Test de la Mirada para niños, El Test de Metidas de Pata, e Historias Extrañas de Happé. Los resultados se discuten a la luz de la literatura científica sobre el tema.Autism Spectrum Disorder (ASD) is a condition that is characterized by failures in social behavior and repetitive behaviors. The neuropsychological profile shows heterogeneous findings that depends on the severity of the disorder. The objective of this paper is to describe the neuropsychological functioning of a sample of children with ASD who attend the Institute for the Integral Development of Children with Autism (DINA). The sample consisted of 78 participants, 15.4 % female and 84.6 % male, aged between 6 and 16 years. The instruments used were the neuropsychological protocol adapted from the ENI, intelligence apportionment from the WISC-IV, Sally and Ann Test, Facial Expressions Test adapted by Paul Ekman and Reading the Mind in the Eye for children, Faux Pas Test, and The Happé's Strange Stories test. The results are discussed considering the scientific literature on the subject