Transposons are important contributors to gene expression variability under selection in rice populations.

Transposable elements (TEs) are an important source of genome variability. Here, we analyze their contribution to gene expression variability in rice by performing a TE insertion polymorphism expression quantitative trait locus mapping using expression data from 208 varieties from the Oryza sativa ssp. indica and O. sativa ssp. japonica subspecies. Our data show that TE insertions are associated with changes of expression of many genes known to be targets of rice domestication and breeding. An important fraction of these insertions were already present in the rice wild ancestors, and have been differentially selected in indica and japonica rice populations. Taken together, our results show that small changes of expression in signal transduction genes induced by TE insertions accompany the domestication and adaptation of rice populations.

Estudio de la bioaccesibilidad in vitro de zinc en arroz (oryza sativa) y su relación con el contenido de ácido fitico / In vitro bioaccesibility of zinc in rice (oryza sativa) and its relationship with phytic acid content

La bioaccesibilidad de un nutriente en un alimento sirve para determinar la calidad nutricional de éste para el consumo humano. El arroz es uno de los alimentos más importantes en la dieta por su gran aporte calórico y nutricional. El objetivo de este estudio fue analizar la bioaccesibilidad in vitro del zinc en arroz mediante espectrofotometría ultravioleta-visible y espectrometría de absorción atómica de llama y su relación con el contenido de ácido fítico. El porcentaje de bioaccesibilidad del zinc, respecto al porcentaje de ácido fítico, presentó una relación logarítmica inversamente proporcional (r= −0,669; p<0,05). Los valores porcentuales de bioaccesibilidad del zinc y ácido fítico en las líneas de arroz evaluadas se hallaron en un rango de 1,98,7% y 0,039-0,946% respectivamente. Se encontró que el ácido fítico afecta la bioaccesibilidad del zinc y que ésta no estuvo ligada a la concentración total del zinc presente en las líneas de arroz evaluadas. Las técnicas implementadas para cuantificar el zinc dializado presentaron diferencias significativas y se mostró que la técnica ultravioleta-visible no fue apta para este tipo de ensayos.

The bioavailability of a nutrient in a food serves to determine the nutritional quality for human consumption. Rice is one of the most important foods in diet due to its caloric and nutritional contribution. The objective of this study was to analyze the in vitro bioavailability of zinc in rice by ultraviolet-visible spectrophotometry and flame atomic absorption spectrometry and its relationship with phytic acid content. The percentage of zinc bioaccessibility with respect to phytic acid percentage, showed an inverse proportional logarithmic relationship (r= −0.669; p<0.05). The percentage values of zinc bioavailability and phytic acid in the evaluated rice varieties had a range of 1.9-8.7% and 0.039-0.946%, respectively. Phytic acid affected the bioaccessibility of zinc and was not linked to the total concentration of zinc present in the rice lines evaluated. The techniques implemented to quantify zinc dialyzed presented significant differences. It was shown that the ultraviolet-visible technique was not suitable for this type of assay.

An optical interferometric technique for assessing ozone induced damage and recovery under cumulative exposures for a Japanese rice cultivar.

Exposure to ozone (O3) causes reduction both in the growth and yield of rice (Oriza sativa L.). Commonly used Chlorophyll fluorescent measurements are not sensitive enough for short term exposure of O3 aiming an immediate assessments. Such a conventional method typically needs exposure over a few days to detect the influence. As an alternative method, we proposed a novel non-invasive, robust, real-time, optical Statistical Interferometric Technique (SIT) to measure growth at an accuracy of 0.1 nm with a commonly consumed Japanese rice cultivar, Koshihikari. In the present study, we have conducted a repetitive O3 exposure experiment for three days under three different concentrations of 0 nl l(-1) (control), 120 nl l(-1), and 240 nl l(-1), to investigate the damage and recovery strengths. As a measure to assess the effect and recovery from three consecutive day exposures of O3, we measured the elongation rate (nm mm(-1) sec(-1)) every 5.5 sec for 7 hours, and it revealed nanometric elongation rate fluctuations or Nanometric Intrinsic Fluctuations (NIF). Comparing the standard deviation (SD) of normalized nanometric intrinsic fluctuations (NNIF), which was normalized by that before the exposure, we found that drastic reductions under both 120 nl l(-1) and 240 nl l(-1) O3 concentrations. Reduction percentages were large under high O3 concentration of 240 nl l(-1) indicating the possibility of irreversible effect. However exposure to 120 nl l(-1) of O3 showed recovery on the 2(nd) and 3(rd) days. While SIT did reveal immediate effect based on an observation for a few hours, the visible foliar effect could be observed only after a week. Hence, the technique could provide a way for fast assessment of effect and recovery due to cumulative exposure of O3 and hence the tolerance as well as the vitality of plant.

Caracterização e influência de rizóbios isolados de alfafa na germinação e desenvolvimento inicial de plântulas de arroz / Characterization and influence of alfafa rhizobia on germination and early growth of rice seedling

A inoculação de plantas leguminosas com rizóbios é um dos principais métodos biotecnológicos de utilização de micro-organismos em plantas visando à fixação biológica de nitrogênio na agricultura. No entanto, nos últimos anos, vêm sendo observada nesses micro-organismos a capacidade de produção de fitohormônios, principalmente o ácido indol-acético (AIA) e a promoção de crescimento em gramíneas. Dessa forma, os objetivos deste trabalho foram quantificar o ácido indol-acético produzido por rizóbios isolados de alfafa, avaliar o efeito da inoculação desses micro-organismos na germinação de sementes de arroz e realizar a caracterização genética desses isolados. Nove rizóbios isolados de nódulos de alfafa foram avaliados quanto a sua capacidade de produção de equivalentes de AIA e a influência da inoculação desses micro-organismos na germinação e desenvolvimento de plântulas de arroz. Os rizóbios produtores de AIA foram identificados pelo sequenciamento da região do gene 16S do DNAr. A produção de equivalentes ao ácido indol-acético foi observada em todos rizóbios, com valores que variaram de 43,04 a 101,26µg mL-1 em meio de cultura. Com relação à germinação das sementes de arroz, a inoculação com rizóbios acelerou o processo e o crescimento de suas plântulas. Os rizóbios UFRGS Ms58, Ms515, Ms195, Ms205, Ms2010 e 2012 foram identificados como pertencentes à espécie Sinorhizobium meliloti e UFRGS Ms55, Ms72 e Ms75 à espécie Rhizobium sp.

The inoculation of leguminous plants with rhizobia is one of the main methods of biotechnological use of microorganisms in order to obtain biological nitrogen fixation in agriculture. However, in recent years it has been attributed to these microorganisms the ability to produce phytohormones, mainly indole acetic acid (IAA), and to promote the growth in grasses. Thus, the objectives of this study were to quantify the indole acetic acid produced by rhizobia from alfalfa and to evaluate the effect of inoculation of these microorganisms on the germination of rice seed and to perform the genetic characterization of these isolates. Nine rhizobia, from nodules of alfalfa, were evaluated for their ability to produce IAA equivalents and for their influence in inoculating these microorganisms on germination and seedling development of rice. Moreover, these rhizobia producers of IAA were identified by the 16S region of DNAr. The equivalent production of indole acetic acid was observed in all tested isolates, with values ranging from 43.04 to 101.26µg mL-1 in culture medium. Regarding the germination of rice seeds, the inoculation with rhizobia accelerated this germination and its growth. Microorganisms UFRGS Ms58, UFRGS Ms515, UFRGS Ms195, UFRGS Ms205, UFRGS Ms2010 and UFRGS 2012 were identified as belonging to the species of Sinorhizobium meliloti. Microorganisms Ms55 UFRGS, UFRGS Ms75 and UFRG Ms72 were identified as belonging to the species of Rhizobium sp.