title: Trichome patterning control involves TTG1 interaction with SPL transcription factors.
abstract: Epidermal cell differentiation is a paramount and conserved process among plants. In Arabidopsis, a ternary complex formed by MYB, bHLH transcription factors and TTG1 modulates unicellular trichome morphogenesis. The formation of multicellular glandular trichomes of the xerophytic shrub Cistus creticus that accumulate labdane-type diterpenes, has attained much attention renowned for its medicinal properties. Here, we show that C. creticus TTG1 (CcTTG1) interacts with the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPLA/B) proteins, putative homologs of AtSPL4/5 that in turn interact with AtTTG1. These interactions occur between proteins from evolutionarily distant species supporting the conserved function of TTG1-SPL complex. Overexpression of AtSPL4 and AtSPL5 decreased the expression of GLABRA2 (AtGL2), the major regulator of trichome morphogenesis, resulting in trichome reduction on the adaxial surface of cauline leaves, thereby illuminating the significance of TTG1-SPLs interactions in trichome formation control. AtGL2 and AtSPL4 have opposite expression patterns during early stages of leaf development. We postulate an antagonistic effect between SPLs and the heterogeneous MYB-bHLH factors binding to TTG1. Hence, the SPLs potentially rearrange the complex, attenuating its transcriptional activity to control trichome distribution.
authors.affiliation: Group of Biotechnology of Pharmaceutical Plants, Laboratory of Pharmacognosy, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Ioannidi
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
authors.forename: Stamatis
authors.initials: S
authors.lastname: Rigas
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
authors.forename: Dikran
authors.initials: D
authors.lastname: Tsitsekian
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
authors.forename: Gerasimos
authors.initials: G
authors.lastname: Daras
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
authors.forename: Anastasios
authors.initials: A
authors.lastname: Alatzas
authors.affiliation: Institute of Applied Biosciences, CERTH, Thessaloniki, Greece.
authors.forename: Antonis
authors.initials: A
authors.lastname: Makris
authors.affiliation: Group of Biotechnology of Pharmaceutical Plants, Laboratory of Pharmacognosy, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.|Department of Agricultural Sciences, Aristotle University of Thessaloniki, 541 24, Thessaloniki, Greece.
authors.forename: Georgia
authors.initials: G
authors.lastname: Tanou
authors.affiliation: Institute of Applied Biosciences, CERTH, Thessaloniki, Greece.
authors.forename: Anagnostis
authors.initials: A
authors.lastname: Argiriou
authors.affiliation: Group of Biotechnology of Pharmaceutical Plants, Laboratory of Pharmacognosy, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Alexandrou
authors.affiliation: Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104-6313, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Poethig
authors.affiliation: Department of Biotechnology, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece. phat@aua.gr.
authors.forename: Polydefkis
authors.initials: P
authors.lastname: Hatzopoulos
authors.affiliation: Group of Biotechnology of Pharmaceutical Plants, Laboratory of Pharmacognosy, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece. kanellis@pharm.auth.gr.
authors.forename: Angelos K
authors.initials: AK
authors.lastname: Kanellis
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D029758:Cistus / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D064201:Trichomes / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D014157:Transcription Factors
keywords: Arabidopsis; Cistus creticus; Flavonoids; Root-hairs; TTG1/GL2 pathway; Trichomes