Translation Initiation Factor AteIF(iso)4E Is Involved in Selective mRNA Translation in Arabidopsis Thaliana Seedlings

One of the most regulated steps of translation initiation is the recruitment of mRNA by the translation machinery. In eukaryotes, this step is mediated by the 5′end cap-binding factor eIF4E bound to the bridge protein eIF4G and forming the eIF4F complex. In plants, different isoforms of eIF4E and eIF4G form the antigenically distinct eIF4F and eIF(iso)4F complexes proposed to mediate selective translation. Using a microarray analysis of polyribosome- and non-polyribosome-purified mRNAs from 15 day-old Arabidopsis thaliana wild type [WT] and eIF(iso)4E knockout mutant [(iso)4E-1] seedlings we found 79 transcripts shifted from polyribosomes toward non-polyribosomes, and 47 mRNAs with the opposite behavior in the knockout mutant. The translationally decreased mRNAs were overrepresented in root-preferentially expressed genes and proteins from the endomembrane system, including several transporters such as the phosphate transporter PHOSPHATE1 (PHO1), Sucrose transporter 3 (SUC3), ABC transporter-like with ATPase activity (MRP11) and five electron transporters, as well as signal transduction-, protein modification- and transcription-related proteins. Under normal growth conditions, eIF(iso)4E expression under the constitutive promoter 35 S enhanced the polyribosomal recruitment of PHO1 supporting its translational preference for eIF(iso)4E. Furthermore, under phosphate deficiency, the PHO1 protein increased in the eIF(iso)4E overexpressing plants and decreased in the knockout mutant as compared to wild type. In addition, the knockout mutant had larger root, whereas the 35 S directed expression of eIF(iso)4E caused shorter root under normal growth conditions, but not under phosphate deficiency. These results indicate that selective translation mediated by eIF(iso)4E is relevant for Arabidopsis root development under normal growth conditions

Transcriptional Regulation of zma-MIR528a by Action of Nitrate and Auxin in Maize

In recent years, miR528, a monocot-specific miRNA, has been assigned multifaceted roles during development and stress response in several plant species. However, the transcription regulation and the molecular mechanisms controlling MIR528 expression in maize are still poorly explored. Here we analyzed the zma-MIR528a promoter region and found conserved transcription factor binding sites related to diverse signaling pathways, including the nitrate (TGA1/4) and auxin (AuxRE) response networks. Accumulation of both pre-miR528a and mature miR528 was up-regulated by exogenous nitrate and auxin treatments during imbibition, germination, and maize seedling establishment. Functional promoter analyses demonstrated that TGA1/4 and AuxRE sites are required for transcriptional induction by both stimuli. Overall, our findings of the nitrogen- and auxin-induced zma-MIR528a expression through cis-regulatory elements in its promoter contribute to the knowledge of miR528 regulome

High-throughput profiling of caenorhabditis elegans starvation-responsive microRNAs

MicroRNAs (miRNAs) are non-coding RNAs of ~22 nucleotides in length that regulate gene expression by interfering with the stability and translation of mRNAs. Their expression is regulated during development, under a wide variety of stress conditions and in several pathological processes. In nature, animals often face feast or famine conditions. We observed that subjecting early L4 larvae from Caenorhabditis elegans to a 12-hr starvation period produced worms that are thinner and shorter than well-fed animals, with a decreased lipid accumulation, diminished progeny, reduced gonad size, and an increased lifespan. Our objective was to identify which of the 302 known miRNAs of C. elegans changed their expression under starvation conditions as compared to well-fed worms by means of deep sequencing in early L4 larvae. Our results indicate that 13 miRNAs (miR-34-3p, the family of miR-35-3p to miR-41-3p, miR-39-5p, miR-41-5p, miR-240-5p, miR-246-3p and miR-4813-5p) were upregulated, while 2 miRNAs (let-7-3p and miR-85-5p) were downregulated in 12-hr starved vs. well-fed early L4 larvae. Some of the predicted targets of the miRNAs that changed their expression in starvation conditions are involved in metabolic or developmental process. In particular, miRNAs of the miR-35 family were upregulated 6-20 fold upon starvation. Additionally, we showed that the expression of gld-1, important in oogenesis, a validated target of miR-35-3p, was downregulated when the expression of miR-35-3p was upregulated. The expression of another reported target, the cell cycle regulator lin-23, was unchanged during starvation. This study represents a starting point for a more comprehensive understanding of the role of miRNAs during starvation in C. elegans

Time to Wake Up: Epigenetic and Small-RNA-Mediated Regulation during Seed Germination

Plants make decisions throughout their lifetime based on complex networks. Phase transitions during seed growth are not an exception. From embryo development through seedling growth, several molecular pathways control genome stability, environmental signal transduction and the transcriptional landscape. Particularly, epigenetic modifications and small non-coding RNAs (sRNAs) have been extensively studied as significant handlers of these processes in plants. Here, we review key epigenetic (histone modifications and methylation patterns) and sRNA-mediated regulatory networks involved in the progression from seed maturation to germination, their relationship with seed traits and crosstalk with environmental inputs

Caracterización de patrones de hordeínas en variedades mexicanas de cebada maltera

A group of storage proteins highly abundant in cereal seeds are the prolamins, characterized by the frequent presence of proline in their sequence. The barley prolamins are known as hordeins. The aim of this study was to obtain the hordein banding patterns for five different Mexican barley cultivars in mature seeds. In addition, the hordein patterns in processed malt of four mexican and a canadian (Metcalfe) barley cultivars were obtained. Mass Spectrometry (MS), using distinct digestion protocols, identified differential bands in the patterns. Major differences in the seed patterns between cultivars consisted in discrete bands at 100 kDa, 65 kDa and in the range of 37 to 45 kDa. In malt, the patterns were highly contrasting among Mexican cultivars as well as in Metcalfe, suggesting that hordein processing during germination and malt processing is particular to each cultivar. Finally, the MS identification demonstrated that trypsin digestion is appropriate to distinguish B and γ hordeins in malt, whereas sequential digestion with chymotrypsin and trypsin allows the identification of C hordeins in seed.Un grupo de proteínas de almacenamiento muy abundantes en la semilla de cereales son las prolaminas que se caracterizan por contener muchos residuos de prolina en su secuencia. En cebada, las prolaminas son denominadas hordeínas. El propósito de este estudio fue obtener los patrones proteicos de bandeo mediante la técnica de electroforesis en gel de poliacrilamida bajo condiciones desnaturalizantes para, hordeínas de semilla seca de cinco variedades mexicanas de cebada. Asimismo, se obtuvieron los patrones de hordeínas en malta procesada a partir de cuatro variedades mexicanas y una variedad canadiense (Metcalfe). A continuación, algunas de las bandas diferenciales fueron identificadas mediante espectrometría de masas (EM) utilizando distintos protocolos de digestión. En los patrones de semilla seca se encontraron diferencias entre las variedades mexicanas para las bandas correspondientes a un peso molecular de 100 kDa, 65 kDa y algunas de 37-45 kDa. En el caso de la malta, los patrones de las variedades mexicanas fueron muy contrastantes entre sí, así como con el observado en Metcalfe, lo que sugiere que el procesamiento de hordeínas durante la germinación y el secado de la malta depende de cada variedad. Finalmente, en la identificación por EM se demostró que el uso de digestión con tripsina es adecuado para distinguir hordeínas B y γ en malta, mientras que el uso de digestión secuencial con quimotripsina y tripsina favorece la identificación de hordeínas C en semilla seca

Caracterización de patrones de hordeínas en variedades mexicanas de cebada maltera

Un grupo de proteínas de almacenamiento muy abundantes en la semilla de cereales son las prolaminas que se caracterizan por contener muchos residuos de prolina en su secuencia. En cebada, las prolaminas son denominadas hordeínas. El propósito de este estudio fue obtener los patrones proteicos de bandeo mediante la técnica de electroforesis en gel de poliacrilamida bajo condiciones desnaturalizantes para, hordeínas de semilla seca de cinco variedades mexicanas de cebada. Asimismo, se obtuvieron los patrones de hordeínas en malta procesada a partir de cuatro variedades mexicanas y una variedad canadiense (Metcalfe). A continuación, algunas de las bandas diferenciales fueron identificadas mediante espectrometría de masas (EM) utilizando distintos protocolos de digestión. En los patrones de semilla seca se encontraron diferencias entre las variedades mexicanas para las bandas correspondientes a un peso molecular de 100 kDa, 65 kDa y algunas de 37-45 kDa. En el caso de la malta, los patrones de las variedades mexicanas fueron muy contrastantes entre sí, así como con el observado en Metcalfe, lo que sugiere que el procesamiento de hordeínas durante la germinación y el secado de la malta depende de cada variedad. Finalmente, en la identificación por EM se demostró que el uso de digestión con tripsina es adecuado para distinguir hordeínas B y γ en malta, mientras que el uso de digestión secuencial con quimotripsina y tripsina favorece la identificación de hordeínas C en semilla seca