RBE controls microRNA164 expression to effect floral organogenesis

Abstract

Genetic stocks and growth conditionsArabidopsis thaliana plants were grown at 22°C under 16-hour light/8-hour dark conditions. The rbe-2 (Salk_037010), rbe-3, mir164b-1 (Salk_136105), cuc1-1 and cuc2-1 seeds were obtained from the Arabidopsis Biology Resource Center (ABRC). mir164a-4 (GABI SUMMARYThe establishment and maintenance of organ boundaries are vital for animal and plant development. In the Arabidopsis flower, three microRNA164 genes (MIR164a, b and c) regulate the expression of CUP-SHAPED COTYLEDON1 (CUC1) and CUC2, which encode key transcriptional regulators involved in organ boundary specification. These three miR164 genes are expressed in distinct spatial and temporal domains that are crucial for their function. Here, we show that the C2H2 zinc finger transcriptional repressor encoded by RABBIT EARS (RBE) regulates the expression of all three miR164 genes. Furthermore, we demonstrate that RBE directly interacts with the promoter of MIR164c and negatively regulates its expression. We also show that the role of RBE in sepal and petal development is mediated in part through the concomitant regulation of the CUC1 and CUC2 gene products. These results indicate that one role of RBE is to fine-tune miR164 expression to regulate the CUC1 and CUC2 effector genes, which, in turn, regulate developmental events required for sepal and petal organogenesis.KEY WORDS: Arabidopsis, miRNA, Flower development RBE controls microRNA164 expression to effect floral organogenesis

SUPERMAN prevents class B gene expression and promotes stem cell termination in the fourth whorl of Arabidopsis thaliana flowers

“…It is not surprising, however, for a boundary gene to control cell proliferation, as cell division rates are lower at boundaries, including the boundary between stamens and carpels, than in developing organs (2,26). For instance, RABBIT EARS (RBE), which encodes a C2H2 zinc-finger protein related to SUP, specifies the boundary between whorls 2 and 3 by excluding AG from whorl 2 (27,28), and also specifies the intersepal boundaries by regulating cell proliferation in whorl 1 via the miR164/CUP-SHAPED COTYLEDON (CUC) module (29).…”

Floral Organogenesis: When Knowing Your ABCs Is Not Enough

“…RBE has been shown to act directly downstream of the B function regulators APETALA3 (AP3) and PISTILLATA (PI; Wuest et al, 2012), which are involved in the specification of petals and stamens. During petal initiation, RBE controls the microRNA miR164-dependent pathway (Huang et al, 2012), which mediates boundary formation in-between organ primordia via regulation of CUP-SHAPED COTYLEDON genes (Sieber et al, 2007). During this initial phase of petal development, RBE was found to repress the expression of certain TCP transcription factor-coding genes (Huang and Irish, 2015), which are thought to control the transition from cell division to cell expansion and differentiation during organ growth (Huang and Irish, 2016).…”

Auxin controls petal initiation in Arabidopsis

“…As with PTL, RBE also dampens growth between developing sepals (Krizek et al, 2006). However, the mechanism of its growth suppression differs from that of PTL (Lampugnani et al, 2012) because RBE promotes the action of CUP-SHAPED COTYLEDON boundary genes through direct repression of their negative regulator EXTRA EARLY PETALS1 (Huang et al, 2012). Also, RBE normally represses AGAMOUS expression in the second whorl (Krizek et al, 2006), but PTL does not (Griffith et al, 1999).…”