Comparative Genomics of NAC Transcriptional Factors in Angiosperms: Implications for the Adaptation and Diversification of Flowering Plants.

NAC proteins constitute one of the largest groups of plant-specific transcription factors and are known to play essential roles in various developmental processes. They are also important in plant responses to stresses such as drought, soil salinity, cold, and heat, which adversely affect growth. The current knowledge regarding the distribution of NAC proteins in plant lineages comes from relatively small samplings from the available data. In the present study, we broadened the number of plant species containing the NAC family origin and evolution to shed new light on the evolutionary history of this family in angiosperms. A comparative genome analysis was performed on 24 land plant species, and NAC ortholog groups were identified by means of bidirectional BLAST hits. Large NAC gene families are found in those species that have experienced more whole-genome duplication events, pointing to an expansion of the NAC family with divergent functions in flowering plants. A total of 3,187 NAC transcription factors that clustered into six major groups were used in the phylogenetic analysis. Many orthologous groups were found in the monocot and eudicot lineages, but only five orthologous groups were found between P. patens and each representative taxa of flowering plants. These groups were called basal orthologous groups and likely expanded into more recent taxa to cope with their environmental needs. This analysis on the angiosperm NAC family represents an effort to grasp the evolutionary and functional diversity within this gene family while providing a basis for further functional research on vascular plant gene families

Phylogenetic relationships among 24 land plant species and the distribution of NAC proteins identified in this study, based on the HMM-generated profile.

<p>The total number of NAC proteins identified in each genome; the plant genome size, ploidy and chromosome number of each species; and the number of NAC sequences with Transmembrane motifs (TMM) for each genome are indicated on the right in colored squares. Ancient WGDs are represented by colored stars (details were taken from CoGepedia, <a href="https://genomevolution.org/" target="_blank">https://genomevolution.org</a>). Species names are color-coded as follows: blue–Moss, purple–pseudofern, red—monocots, and green—eudicots. * Genome size in Gb.</p

Schematic representation of NAC OGs shared among Angiosperms.

<p>A) Venn diagram showing the orthologous gene number shared between the <i>P</i>. <i>patens</i> outgroup and rice and grapevine genomes as the selected representatives for monocot and eudicot plants, respectively. The total overlap consisted of five proteins that define the basal core of the NAC genes. B) The number of orthologous proteins detected by means of BBH in 24 green plants. Green lines indicate the OGs shared between the moss <i>P</i>. <i>paten</i>, <i>S</i>. <i>moellendorffii</i>, and the basal taxa of the monocot and eudicot lineages. The number below the red line indicates the number of OGs shared between the rice and grapevine species. Black lines indicate the number of OGs shared among the monocots and eudicots with their respective selected pivotal species.</p

Plant E2F factors in cell cycle, development and DNA damage response

During the past ten years, emerging data revealed the role of E2F factors in various plant physiology aspects. E2F involvement in cell cycle and plant development was particularly investigated and highlighted some plant specificities, espacially in postembryonic development. A major role of E2F is its transcriptional activity governing specific gene induction throughout the cell cycle and also strong induction of DNA repair genes in response to DNA damage, notably in the context of DNA double strand break (DSB) response. More challenging is the implication of E2F in nuclear foci with gamma-H2AX, a marker of DSB, probably independently of its transcriptional activity, in the DNA damage response