Abstract
NAC (NAM, ATAF1,2, and CUC2) transcription factors are one of the largest transcription factor families found in the plants and are involved in diverse developmental and signalling events. Despite the availability of comprehensive genomic information from diverse plant species, the basic genomic, biochemical, and evolutionary details of NAC TFs have not been established. Therefore, NAC TFs family proteins from 160 plant species were analyzed in the current study. Study revealed, Brassica napus (410) encodes highest number and Klebsormidium flaccidum (3) encodes the lowest number of TFs. The study further revealed the presence of NAC TF in the Charophyte algae K. flaccidum. On average, the monocot plants encode higher number (141.20) of NAC TFs compared to the eudicots (125.04), gymnosperm (75), and bryophytes (22.66). Furthermore, our analysis revealed that several NAC TFs are membrane bound and contain monopartite, bipartite, and multipartite nuclear localization signals. NAC TFs were also found to encode several novel chimeric proteins and regulate a complex interactome network. In addition to the presence of NAC domain, several NAC proteins were found to encode other functional signature motifs as well. Relative expression analysis of NAC TFs in A. thaliana revealed root tissue treated with urea and ammonia showed higher level of expression and leaf tissues treated with urea showed lower level of expression. The synonymous codon usage is absent in the NAC TFs and it appears that they have evolved from orthologous ancestors and undergone vivid duplications to give rise to paralogous NAC TFs. The presence of novel chimeric NAC TFs are of particular interest and the presence of chimeric NAC domain with other functional signature motifs in the NAC TF might encode novel functional properties in the plants.
Highlights
Next-generation sequencing (NGS) has fostered the sequencing of many plant genomes
NAC transcription factors exhibit diverse genomic and biochemical features Advancements in genome sequencing technology have enabled the discovery of the genomic details of large number of plant species
Except for Hordeum vulgare (76), Saccharum officinarum (44), and Zostera marina (62) all other monocot species possess more than one hundred NAC TFs each (Table 1)
Summary
Next-generation sequencing (NGS) has fostered the sequencing of many plant genomes. The availability of so many genomes has allowed researchers to readily identify genes, examine genetic diversity within a species, and gain insight into the evolution of genes and gene families. Gene expression is regulated in part by different families of proteins known as transcription factors (TFs) [1,2,3,4]. The TFs are involved in inducing the transcription of DNA into RNA [5,6,7,8]. They include numerous and diverse proteins, all of which contain one or more DNAbinding motifs [8,9,10]. Some TFs bind to a DNA promoter region located near the transcription start site of a gene and help to form the transcription initiation complex [13,14,15,16]. There are at least 52 different TF families in the Arabidopsis thaliana, and the NAC (no apical meristem (NAM) TF family is one of them
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