Class I TCPs modulate cytokinin-induced branching and meristematic activity in tomato

Abstract

Arabidopsis TCPs are a family of basic helix loop helix (bHLH)-type transcription factors. Previous studies suggested that antagonistic activities of class I TCPs and class II TCPs are correlated with cell proliferation. We have recently shown that the class I TCPs AtTCP14 and AtTCP15 promote typical cytokinin (CK) responses in Arabidopsis, and proposed that they mediate the effect of CK on cell divisions. To further study the role of AtTCP14 and AtTCP15 in plant development, we expressed them in tomato plants. AtTCP14 and AtTCP15-expressing tomato plants were semi-dwarf, had a reduced apical dominance and developed ectopic meristems on leaflet petioles. CK application to tomato seedlings promoted axillary bud outgrowth and this effect was enhanced in the transgenic AtTCP14 and AtTCP15 overexpressing plants. The results of this study extend our previous suggestion that AtTCP14 and AtTCP15 modulate the plant sensitivity to CK.

TomatoHAIRY MERISTEMgenes are involved in meristem maintenance and compound leaf morphogenesis

“…Consistent with that, in tomato, increased CK levels or signaling cause the formation of ectopic meristems on the adaxial side of the leaf rachis and leaflet petiolules (Shani et al , 2010; Steiner et al , 2012). Since CK was shown to promote WUS expression in meristems (Gordon et al , 2009), the expansion of the WUS domain in meristems silenced for SlHAM s may imply that CK status increased in these meristems.…”

“…In tomato, elevation of cytokinin (CK) levels or response enhancement led to the proliferation of ectopic shoot and inflorescence meristems on the adaxial side of the compound leaf rachis which is highly reminiscent of the phenotype observed in FIL>>MIR171b later developed leaves (Janssen et al , 1998; Kim et al , 2003; Shani et al , 2010; Steiner et al , 2012). This suggested that an increased CK level or response may be the cause of the abnormal cell proliferation observed in later developed leaf rachises of FIL>>MIR171b plants.…”

A Role for APETALA1/FRUITFULL Transcription Factors in Tomato Leaf Development

“…It has been previously suggested that class I and class II TCPs affect growth in an antagonistic manner (Li et al, 2005;Hervé et al, 2009;Koyama et al, 2010;Martín-Trillo and Cubas, 2010). Class I TCPs were recently shown to promote CK responses in both Arabidopsis and tomato (Steiner et al, 2012a(Steiner et al, , 2012b, and Arabidopsis CIN-TCP were shown to dampen CK response by activating ARR16 via an interaction with the chromatin-modifying complex BRM (Efroni et al, 2013). Moreover, BRM was recently shown to affect GA biosynthesis and response (Archacki et al, 2013).…”

Analysis of the role of Arabidopsis class I TCP genes AtTCP7, AtTCP8, AtTCP22, and AtTCP23 in leaf development

“…AtTCP15, along with its closest homolog AtTCP14, has a role in internode length and leaf shape (Kieffer et al, 2011). Both AtTCP14 and AtTCP15 are found to interact with SPINDLY (SPY) to promote cytokinin responses (Steiner et al, 2012a) and increase the sensibility to this hormone when overexpressed in tomato (Steiner et al, 2012b). …”