Cysteine-rich polycomb-like proteins (CPP) are a small family of transcription factors (TFs) widely distributed in plants and animals except fungi (Andersen et al., 2007). CPPs play a significant role in plant cell division, reproductive tissue development and response to abiotic stress (Yang et al., 2008). The characteristic feature of CPP transcription factor that is highly conserved among all species is 1 or 2 cysteine rich domains (CXC) that can bind DNA and regulate gene expression (Hauser et al., 2000). Eight members of this family are present in Arabidopsis, 11 in rice, 13 in Maize, 20 in soybean (Yang et al., 2008, Song et al., 2016, Zang et al., 2015). Plant CPP proteins can be divided into group I and group II based on CXC domain location and Pfam-B_9804 domain is located at N-terminal in most of the group I proteins and Pfam-B_12915 is located at C-terminal in group II proteins, however consensus CXC domain sequences are similar in both group of proteins (Lu et al., 2013). The 13 members of the Maize CPP family are distributed unevenly across 6 of 10 chromosomes, with activity mainly in the nucleus (Song et al., 2016). Only two CPP family members (TSO1 in Arabidopsis and CPP1 in soyabean) have been studied so far.

The first member TSO1 of this family was identified in Arabidopsis through map-based cloning and its functions were determined through mutant screen. Mutant tso1-1 resulted in defects in mitosis and cytokinesis during flower development resulting in incomplete cell wall formation, disorganized flower meristem layers, irregular nuclei size and shape, abnormal size and shape of sepals. However, TSO1-1 defects were strictly restricted to cell division during the flowering stage of plant development (Liu et al., 1997). In another study, weaker TSO1 alleles TSO1-3 and TSO1-4 were identified to be important players in ovule development, since mutant tso1-3  and tso1-4 caused loss of control of directional ovule cell expansion and adjacent cell enlargement co-ordination, therefore highlighting TSO1 role in both cell division and  cell expansion in floral morphogenesis (Hauser et al., 1998). In soyabean, CPP1 interacts with the promoter of leghaemoglobin gene Gmlbc3 and negatively regulates its expression in the symbiotic root nodule (Cvitanich et al., 2000). In Maize, on the basis of expression profile analysis by qRT-PCR most ZmCPPs were upregulated and showed similar expression patterns in response to heat and cold stress, thus indicating their role in abiotic stress response (Song et al., 2016). In Arabidopsis, TSO1 with MYB3R1 forms a part of cell cycle regulatory complex, DREAM complex and coordinately regulates stem and root cell proliferation and differentiation (Wang et al.,2018).

Last updated June 2023 by Ankita Abnave

References:

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Zhang L, Zhao HK, Wang YM, Yuan CP, Zhang YY, Li HY, Yan XF, Li QY, Dong YS. Genome-wide identification and expression analysis of the CPP-like gene family in soybean. Genet Mol Res. 2015 Feb 13;14(1):1260-8. doi: 10.4238/2015.February.13.4. PMID: 25730064.

Lu T, Dou Y, Zhang C. Fuzzy clustering of CPP family in plants with evolution and interaction analyses. BMC Bioinformatics. 2013;14 Suppl 13(Suppl 13):S10. doi: 10.1186/1471-2105-14-S13-S10. Epub 2013 Oct 1. PMID: 24268301; PMCID: PMC3849782.

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Song XY, Zhang YY, Wu FC, Zhang L. Genome-wide analysis of the maize (Zea may L.) CPP-like gene family and expression profiling under abiotic stress. Genet Mol Res. 2016 Jul 29;15(3). doi: 10.4238/gmr.15038023. PMID: 27525875.

Cvitanich C, Pallisgaard N, Nielsen KA, Hansen AC, Larsen K, Pihakaski-Maunsbach K, Marcker KA, Jensen EO. CPP1, a DNA-binding protein involved in the expression of a soybean leghemoglobin c3 gene. Proc Natl Acad Sci U S A. 2000 Jul 5;97(14):8163-8. doi: 10.1073/pnas.090468497. PMID: 10859345; PMCID: PMC16687.

Wang W, Sijacic P, Xu P, Lian H, Liu Z. Arabidopsis TSO1 and MYB3R1 form a regulatory module to coordinate cell proliferation with differentiation in shoot and root. Proc Natl Acad Sci U S A. 2018 Mar 27;115(13):E3045-E3054. doi: 10.1073/pnas.1715903115. Epub 2018 Mar 13. PMID: 29535223; PMCID: PMC5879663.