New insights on the evolution of nucleolar dominance in newly resynthesized hexaploid wheat Triticum zhukovskyi

Nucleolar dominance (ND) is a widespread epigenetic phenomenon in hybridizations where nucleolus transcription fails at the nucleolus organizer region (NOR). However, the dynamics of NORs during the formation of Triticum zhukovskyi (GGAu Au Am Am ), another evolutionary branch of allohexaploid wheat, remains poorly understood. Here, we elucidated genetic and epigenetic changes occurring at the NOR loci within the Am , G, and D subgenomes during allopolyploidization by synthesizing hexaploid wheat GGAu Au Am Am and GGAu Au DD. In T. zhukovskyi, Au genome NORs from T. timopheevii (GGAu Au ) were lost, while the second incoming NORs from T. monococcum (Am Am ) were retained. Analysis of the synthesized T. zhukovskyi revealed that rRNA genes from the Am genome were silenced in F1 hybrids (GAu Am ) and remained inactive after genome doubling and subsequent self-pollinations. We observed increased DNA methylation accompanying the inactivation of NORs in the Am genome and found that silencing of NORs in the S1 generation could be reversed by a cytidine methylase inhibitor. Our findings provide insights into the ND process during the evolutionary period of T. zhukovskyi and highlight that inactive rDNA units may serve as a 'first reserve' in the form of R-loops, contributing to the successful evolution of T. zhukovskyi.

Ancient wheats: beneficial effects on insulin resistance

Non-alcoholic fatty liver disease and type 2 diabetes mellitus are two conditions that commonly exist together in the context of the metabolic syndrome. Several scientific advances in understanding this association have identified insulin resistance as the key point in the pathogenesis of both diseases. The first line treatment suggested in the management of these diseases is represented by lifestyle changes and in particular the modification of alimentary regimen, with the transition to a healthy diet. In this context, several studies have focused their attention on the identification of food products with beneficial actions, like ancient wheat (AW). AW are defined as the early cereals that were domesticated in their places of origin in the "Fertile Crescent" of the Middle East, and played a central role as a main source of food for the early civilizations in that region. The present narrative review aims to provide a systematic overview of the state of the art on the effects of AW on insulin resistance.

Tracing the ancestry of modern bread wheats

For more than 10,000 years, the selection of plant and animal traits that are better tailored for human use has shaped the development of civilizations. During this period, bread wheat (Triticum aestivum) emerged as one of the world's most important crops. We use exome sequencing of a worldwide panel of almost 500 genotypes selected from across the geographical range of the wheat species complex to explore how 10,000 years of hybridization, selection, adaptation and plant breeding has shaped the genetic makeup of modern bread wheats. We observe considerable genetic variation at the genic, chromosomal and subgenomic levels, and use this information to decipher the likely origins of modern day wheats, the consequences of range expansion and the allelic variants selected since its domestication. Our data support a reconciled model of wheat evolution and provide novel avenues for future breeding improvement.