TAP Subfamily: C2HDZ
The homeobox TF superfamily is defined by an occurrence of the characteristic homeodomain (HD) and can be defined as pan-eukaryotic since it is found in all eukaryotic organisms (Catarino et al., 2016; Romani et al., 2018). According to different references (e.g., (Catarino et al., 2016; Mukherjee et al., 2009; Que et al., 2018)), the HD superfamily is divided into 11 subfamilies, namely BEL, DDT, HDZ, KNOX, LD, NDX, PHD, PINTOX, PLINC, SAWADEE and WOX. Interestingly, all subfamilies evolved in the common ancestor, before terrestrialization and diversification of land plants (Catarino et al., 2016). Furthermore, the broad distribution and high conservation of domains induces a common highly conserved functional role in plants and whenever members are present, also in algae (Mukherjee et al., 2009). In general, homeobox TFs show diverse functions in developmental and physiological mechanisms (Romani et al., 2018). The HD-HDZ (HDZ) subfamily can be subdivided into four classes, namely classes C1HDZ, C2HDZ, C3HDZ and C4HDZ. The members of these classes exhibit a characteristic homeodomain and an additional leucine zipper (LZ) domain (Romani et al., 2018). Furthermore, in C2HDZ proteins an aromatic, large hydrophobic, acidic context (AHA)-like motif appears (Romani et al., 2018). Also, in C2HDZ proteins there are two additional exclusive motifs, in fact the C-terminal CPSCE sequence and the N-terminal ZIBEL-like motif (Romani et al., 2018). In addition, C3HDZ proteins exhibit a unique MEKHLA domain and 3HDZ and C4HDZ proteins show START/SAD domains (Romani et al., 2018).
References:
Catarino, B., Hetherington, A. J., Emms, D. M., Kelly, S., & Dolan, L. (2016). The Stepwise Increase in the Number of Transcription Factor Families in the Precambrian Predated the Diversification of Plants On Land. Molecular Biology and Evolution, 33(11), 2815–2819. https://doi.org/10.1093/molbev/msw155
Romani, F., Reinheimer, R., Florent, S. N., Bowman, J. L., & Moreno, J. E. (2018). Evolutionary history of HOMEODOMAIN LEUCINE ZIPPER transcription factors during plant transition to land. New Phytologist, 219(1), 408–421. https://doi.org/10.1111/nph.15133
Mukherjee, K., Brocchieri, L., & Burglin, T. R. (2009). A Comprehensive Classification and Evolutionary Analysis of Plant Homeobox Genes. Molecular Biology and Evolution, 26(12), 2775–2794. https://doi.org/10.1093/molbev/msp201
Que, F., Wang, G.-L., Li, T., Wang, Y.-H., Xu, Z.-S., & Xiong, A.-S. (2018). Genome-wide identification, expansion, and evolution analysis of homeobox genes and their expression profiles during root development in carrot. Functional & Integrative Genomics, 18(6), 685–700. https://doi.org/10.1007/s10142-018-0624-x
