Isolation and characterization of maize (Zea mays L.) mitochondrial polyribosomes

Maize mitochondrial polyribosomes were isolated and characterized in the first and so far most complete study of the polysomal component of the translational apparatus of higher plant mitochondrial. Higher plant mitochondria are unique in that more than one, and often many, transcripts for a mitochondrial particular gene are found in abunDance; This made the characterization of the mRNA content of maize mitochondrial polyribosomes crucial to the understanding of information storage and use in these organelles;The protein gene transcript content of mitochondrial polysomes was described and compared to whole mitochondrial transcript content for seven maize mitochondrial genes. It was found that some selection among the multiple transcripts of several maize mitochondrial protein genes occurs at the polysomal level. For instance, the abundant 4.0 transcript of the atp6 gene was entirely missing from multimeric mitochondrial polysomal RNA. Most striking, however, was the observation that the majority of abundant transcripts of individual mitochondrial genes are bound to polysomes. This observation, coupled with recent reports that all plant mitochondrial polysomal transcripts sequenced to date are fully edited at the RNA level, suggests at least two hypotheses concerning gene expression in higher plant mitochondria: (1) there existed in the progenitors of these organelles a permissive transcription apparatus, and the (now nuclear) genome of the host evolved editing machinery to regulate the availability of the promiscuous transcripts to the mitochondrial translational apparatus; and/or (2) RNA editing and association with polysomes in plant mitochondria are developmentally and/or environmentally regulated in order to allow differential expression of the genome under different circumstances. Because only one developmental stage (dark-grown shoots) was studied in this work, this latter hypothesis remains an intriguing possibility;In addition, the translational regulation of a commercially important maize mitochondrial gene involved in cytoplasmic male sterility, T-urf13, was investigated in a revertant line. Cytoplasmic male sterility in race T maize (CMS-T) has been demonstrated to be strongly correlated with the levels of T-URF13 in CMS-T mitochondria. The levels of T-URF13 in TRf (revertant) maize are 25 to 40% of those in CMS-T mitochondria. Regardless of this, equal amounts of T-urf13 translatable in wheat germ extracts exist in both cytoplasms. In addition, work described in this dissertation indicates that preferential degradation of T-URF13 does not occur in TRf mitochondria. It was found that multimeric polysomes in CMS-T and -TRf mitochondria contain similar levels of T-urf13 transcripts, although there seems to be some enrichment of these transcripts in higher-order polysomes in CMS-TRf versus -T. T-URF13 levels associated with multimeric polysomes in the mitochondria of the two cytoplasms are lower (about 40% less) in CMS-TRf than -T. Apparently, similar levels of polysomally-bound transcripts do not necessarily yield similar, steady-state levels of polypeptide, at least in the case of T-urf13

Drama, Poetry and Music in Late-Renaissance Italy: The life and works of Leonora Bernardi

Leonora Bernardi (1559-1616), a gentlewoman of Lucca, was a highly regarded poet, dramatist and singer. She was active in the brilliant courts of Ferrara and Florence at a time when creative women enjoyed exceptional visibility in Italy. Like many such figures, she has since suffered historical neglect. Drama, Poetry and Music in Late-Renaissance Italy presents the first ever study of Bernardi’s life, and modern edition of her recently discovered literary corpus, which mostly exists in manuscript. Her writings appear in the original Italian with new English translations, scholarly notes, critical essays and contributions by Eric Nicholson, Eugenio Refini and Davide Daolmi. Based on new archival research, the substantial opening section reconstructs Bernardi’s unusually colourful life. Bernardi’s works reveal her connections with some of the most pioneering poets, dramatists and musicians of the day, including her mentor Angelo Grillo and the first opera librettist Ottavio Rinuccini. The second major section presents her pastoral tragicomedy Clorilli, one of the earliest secular dramatic works by a woman. It was apparently performed in the early 1590s at a Medici villa near Florence, before Grandduke Ferdinando I de’ Medici, and his consort Christine of Lorraine, but now exists in an enigmatic Venetian manuscript. The third section presents Bernardi’s secular and religious verse, which engaged with new trends in lyric and poetry for music, and was set by various key composers across Italy