Cytokinin Signaling Activates WUSCHEL Expression during Axillary Meristem Initiation

Abstract

The homeodomain transcription factor WUSCHEL (WUS) defines the shoot stem cell niche, but the mechanisms underlying the establishment of WUS expression remain unclear. Here, we show that cytokinin signaling precedes WUS expression in leaf axils and activates WUS expression de novo in the leaf axil to promote axillary meristem initiation. Furthermore, type-B Arabidopsis response regulator proteins, which are transcriptional activators in the cytokinin signaling pathway, directly bind to the WUS promoter and activate its expression. Finally, we show that cytokinin activation of WUS in the leaf axil correlates with increased histone acetylation and methylation markers associated with transcriptional activation, supporting the fact that WUS expression requires a permissive epigenetic environment to restrict it to highly defined meristematic tissues. Taken together, these findings explain how cytokinin regulates axillary meristem initiation and establish a mechanistic framework for the postembryonic establishment of the shoot stem cell niche.

Genetic improvement of the shoot architecture and yield in soya bean plants via the manipulation of GmmiR156b

“…BRANCHED1 ) have been identified (Bell et al ., ; Finlayson, ; Teichmann and Muhr, ). Notably, the homeodomain transcription factor WUSCHEL (WUS), which defines the shoot stem cell niche, is also involved in AM initiation (Wang et al ., ). In rice, several genes, including MONOCULM 1 and two WUS orthologs ( TILLERS ABSENT1 and MONOCUM 3 ), regulate tillering (Lu et al ., ; Tanaka et al ., ).…”

DNA METHYLTRANSFERASE1‐mediated shoot regeneration is regulated by cytokinin‐induced cell cycle in Arabidopsis

“…Auxin acts in the process of shoot induction by the repression of cytokinin biosynthesis (Cheng ZJ et al, 2013), whereas cytokinin regulates the process by the induction of WUS (Gordon et al, 2007;Cheng ZJ et al, 2013). Recent advances have shown that the cytokinin response factors ARABIDOPSIS RESPONSE REGULATORs (ARRs) directly activate WUS expression, and thus initiate shoot meristem formation (Meng et al, 2017;Wang et al, 2017;Zhang et al, 2017;Zubo et al, 2017).…”

Mechanisms of vegetative propagation in bulbs : a molecular approach

“…There is increasing evidence of epigenetic regulation during regeneration (Tanaka et al 2008;Ikeuchi et al 2015;Li et al 2011b;Wang et al 2017). For example, the DNA methyltransferase1 mutant, met1, displays lower levels of DNA methylation and higher expression of WUS during regeneration.…”

“…Thus, it would be interesting to investigate whether the axil of the scales where 'A and B' buds arise do have the competence to initiate more than one bud as well. For instance, it has been reported that a treatment with trichostatin A (TSA), a histone deacetylation inhibitor, together with the synthetic cytokinin BAP, in leaf axils of Arabidopsis, induces the expression of WUSCHEL (WUS), a gene required for the initiation of a shoot meristem (Wang et al 2017). This result in Arabidopsis suggests that axillary bud initiation requires a permissive configuration of the chromatin so that WUS can be induced by a cytokinin pulse (Wang et al 2017).…”

“…For instance, it has been reported that a treatment with trichostatin A (TSA), a histone deacetylation inhibitor, together with the synthetic cytokinin BAP, in leaf axils of Arabidopsis, induces the expression of WUSCHEL (WUS), a gene required for the initiation of a shoot meristem (Wang et al 2017). This result in Arabidopsis suggests that axillary bud initiation requires a permissive configuration of the chromatin so that WUS can be induced by a cytokinin pulse (Wang et al 2017). In line with this hypothesis, it was shown previously that the induction of somatic embryogenesis by auxin, which also involves de novo meristem formation, can be significantly improved by TSA treatment (Li et al 2014a).…”