Massimiliano Lauria

Extensive Maternal DNA Hypomethylation in the Endosperm of Zea mays

A PCR-based genomic scan has been undertaken to estimate the extent and ratio of maternally versus paternally methylated DNA regions in endosperm, embryo, and leaf of Zea mays (maize). Analysis of several inbred lines and their reciprocal crosses identified a large number of conserved, differentially methylated DNA regions (DMRs) that were specific to the endosperm. DMRs were hypomethylated at specific methylation-sensitive restriction sites upon maternal transmission, whereas upon paternal transmission, the methylation levels were similar to those observed in embryo and leaf. Maternal hypomethylation was extensive and offers a likely explanation for the 13% reduction in methyl-cytosine content of the endosperm compared with leaf tissue. DMRs showed identity to expressed genic regions, were observed early after fertilization, and maintained at a later stage of endosperm development. The implications of extensive maternal hypomethylation with respect to endosperm development and epigenetic reprogramming will be discussed.

Epigenetic control of gene regulation in plants.

In eukaryotes, including plants, the genome is compacted into chromatin, which forms a physical barrier for gene transcription. Therefore, mechanisms that alter chromatin structure play an essential role in gene regulation. When changes in the chromatin states are inherited trough mitotic or meiotic cell division, the mechanisms responsible for these changes are defined as epigenetic. In this paper, we review data arising from genome-wide analysis of the epigenetic landscapes in different plant species to establish the correlation between specific epigenetic marks and transcription. In the subsequent sections, mechanisms of epigenetic control of gene regulation mediated by DNA-binding transcription factors and by transposons located in proximity to genes are illustrated. Finally, plant peculiarities for epigenetic control of gene regulation and future perspectives in this research area are discussed. This article is part of a Special Issue entitled: Epigenetic Control of cellular and developmental processes in plants.

The WD40-Repeat Proteins NFC101 and NFC102 Regulate Different Aspects of Maize Development through Chromatin Modification

This work provides insights into the role of chromatin modification in the maize flowering pathway, indicating that WD-repeat proteins NFC101/NFC102 act through different mechanisms to promote a repressive chromatin environment at specific regulators of floral transition. NFC101/NFC102 are also involved in tissue-specific transcription of transposable element repeats and in plant growth rate. The maize (Zea mays) nucleosome remodeling factor complex component101 (nfc101) and nfc102 are putative paralogs encoding WD-repeat proteins with homology to plant and mammalian components of various chromatin modifying complexes. In this study, we generated transgenic lines with simultaneous nfc101 and nfc102 downregulation and analyzed phenotypic alterations, along with effects on RNA levels, the binding of NFC101/NFC102, and Rpd3-type histone deacetylases (HDACs), and histone modifications at selected targets. Direct NFC101/NFC102 binding and negative correlation with mRNA levels were observed for indeterminate1 (id1) and the florigen Zea mays CENTRORADIALIS8 (ZCN8), key activators of the floral transition. In addition, the abolition of NFC101/NFC102 association with repetitive sequences of different transposable elements (TEs) resulted in tissue-specific upregulation of nonpolyadenylated RNAs produced by these regions. All direct nfc101/nfc102 targets showed histone modification patterns linked to active chromatin in nfc101/nfc102 downregulation lines. However, different mechanisms may be involved because NFC101/NFC102 proteins mediate HDAC recruitment at id1 and TE repeats but not at ZCN8. These results, along with the pleiotropic effects observed in nfc101/nfc102 downregulation lines, suggest that NFC101 and NFC102 are components of distinct chromatin modifying complexes, which operate in different pathways and influence diverse aspects of maize development.

Genetic Strategies to Enhance Plant Biomass Yield and Quality- Related Traits for Bio-Renewable Fuel and Chemical Productions

Owing to the increasing concerns on the environment, climate change, and limited natural resources, there are currently considerable efforts applied to produce chemicals and materials from renewable biomass. While initial emphasis has been placed on biofuel production from food plant sugars, the competition between crop usage for food and non-food applications has promoted research efforts to genetically improve yield and quality-related traits for biorefining applications. This chapter summarizes the potential of genetic and biotechnological strategies for improving plant biomass yields and quality-related traits and for breeding varieties more suitable to meet biorefining applications. Attempts were also made to provide a description on the genetic and molecular mechanisms affecting starch, cell wall composition and architecture, and oils synthesis and deposition, including genetic strategies to modify these traits. Similarly, the chapter covers the genetic strategies to improve yields by emphasizing the efforts done to identifying genetic variation and gene(s) governing critical morphological, structural, and physiological traits that in turn influence biomass yields. Finally, in the chapter it is suggested that knowledge of plant biosynthetic pathways will eventually provide valuable opportunities for metabolic engineering, as well as access to chemical transformations unique to plants for breeding varieties with built-in new traits.