LEUNIG (LUG) is an Arabidopsis thaliana transcriptional co-repressor that regulates the floral homeotic gene AGAMOUS (Connor et al., 2000). It is a member of the GroTLE family of transcriptional co-repressors, which do not possess DNA binding motifs but repress a diverse number of target genes through targeted recruitment by site-specific DNA binding transcription factors. Groucho (Gro), which was discovered in Drosophila melanogaster, is the founding member of the highly conserved Gro family of transcriptional corepressors with WD repeats and Q-rich domains (Jennings et al., 2008). Gro family members target specific promoters by interacting with DNA binding transcription factors or other cofactors and they repress transcription by recruiting either HDAC or mediator complexes (Lee et al., 2015).

In Arabidopsis, the 13 members of the Gro family are divided into the LEUNIG (LUG) and TOPLESS (TPL) subclades, but both subclades act as transcriptional corepressors to regulate plant development and hormonal signaling. At LUENIG (LUG) accomplishes binding to site specific DNA binding transcription factors by using an adaptor protein, SEUSS (SEU) (Grigorova et al., 2011). These corepressors affect this repression by interaction with Arabidopsis Mediator components AtMED19/SWP and AtCDK8/HEN3, as well as interaction with histone de-acetylase 19 (HDA19) (Gonzalez et al., 2007). LUG binds DNA indirectly via transcription factors like APETALA1 (AP1), SEPALLATA3 (SEP3), SHORT VEGETATIVE PHASE (SVP), AGL24, and YABBY to repress targets like AG (Lee et al., 2015). The two transcriptional regulators, SEEDSTICK (STK) and LEUNIG-HOMOLOG (LUH), positively regulate seed growth. These factors regulate specific aspects of cell wall properties such as pectin distribution (Di Marzo et al., 2022).

In rice, the floral organ gene KAIKOUXIAO (KKX), mutation produces an uncharacteristic open hull, abnormal seed and semi-sterility. KKX encodes a putative LEUNIG-like (LUGL) transcriptional regulator OsLUGL. A OsLUGL-OsSEU-OsAP1-OsSEP3 complex acts as a transcriptional co-regulator by targeting the promoter of OsGH3-8, then affecting auxin level, OsARFs expression and thereby influencing floral development (Yang et al., 2019).

Last updated June 2023 by John Gray

References:

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Lee N, Park J, Kim K, Choi G. The Transcriptional Coregulator LEUNIG_HOMOLOG Inhibits Light-Dependent Seed Germination in Arabidopsis. Plant Cell. 2015 Aug;27(8):2301-13. doi: 10.1105/tpc.15.00444. Epub 2015 Aug 14. PMID: 26276832; PMCID: PMC4568510.

Jennings BH, Ish-Horowicz D. The Groucho/TLE/Grg family of transcriptional co-repressors. Genome Biol. 2008 Jan 31;9(1):205. doi: 10.1186/gb-2008-9-1-205. PMID: 18254933; PMCID: PMC2395242.

Grigorova B, Mara C, Hollender C, Sijacic P, Chen X, Liu Z. LEUNIG and SEUSS co-repressors regulate miR172 expression in Arabidopsis flowers. Development. 2011 Jun;138(12):2451-6. doi: 10.1242/dev.058362. PMID: 21610026; PMCID: PMC4074289.

Gonzalez D, Bowen AJ, Carroll TS, Conlan RS. The transcription corepressor LEUNIG interacts with the histone deacetylase HDA19 and mediator components MED14 (SWP) and CDK8 (HEN3) to repress transcription. Mol Cell Biol. 2007 Aug;27(15):5306-15. doi: 10.1128/MCB.01912-06. Epub 2007 May 25. PMID: 17526732; PMCID: PMC1952085.

Di Marzo M, Babolin N, Viana VE, de Oliveira AC, Gugi B, Caporali E, Herrera-Ubaldo H, Martínez-Estrada E, Driouich A, de Folter S, Colombo L, Ezquer I. The Genetic Control of SEEDSTICK and LEUNIG-HOMOLOG in Seed and Fruit Development: New Insights into Cell Wall Control. Plants (Basel). 2022 Nov 17;11(22):3146. doi: 10.3390/plants11223146. PMID: 36432874; PMCID: PMC9698089.

Yang C, Liu X, Li D, Zhu X, Wei Z, Feng Z, Zhang L, He J, Mou C, Jiang L, Wan J. OsLUGL is involved in the regulating auxin level and OsARFs expression in rice (Oryza sativa L.). Plant Sci. 2019 Nov;288:110239. doi: 10.1016/j.plantsci.2019.110239. Epub 2019 Aug 29. PMID: 31521225.