Integration of cytokinin and gibberellin signalling byArabidopsistranscription factors GIS, ZFP8 and GIS2 in the regulation of epidermal cell fate

Abstract

The effective integration of hormone signals is essential to normal plant growth and development. Gibberellins (GA) and cytokinins act antagonistically in leaf formation and meristem maintenance and GA counteract some of the effects of cytokinins on epidermal differentiation. However, both can stimulate the initiation of defensive epidermal structures called trichomes. To understand how their relative influence on epidermal cell fate is modulated, we investigated the molecular mechanisms through which they regulate trichome initiation in Arabidopsis. The control by cytokinins of trichome production requires two genes expressed in late inflorescence organs, ZFP8 and GIS2, which encode C2H2 transcription factors related to GLABROUS INFLORESCENCE STEMS (GIS). Cytokinin-inducible GIS2 plays a prominent role in the cytokinin response, in which it acts downstream of SPINDLY and upstream of GLABROUS1. In addition, GIS2 and ZFP8 mediate, like GIS, the regulation of trichome initiation by gibberellins. By contrast, GIS does not play a significant role in the cytokinin response. Collectively, GIS, ZFP8 and GIS2, which encode proteins that are largely equivalent in function, play partially redundant and essential roles in inflorescence trichome initiation and in its regulation by GA and cytokinins. These roles are consistent with their pattern of expression and with the regional influence of GA and cytokinins on epidermal differentiation. Our findings show that functional specialization within a transcription factor gene family can facilitate the integration of different developmental cues in the regulation of plant cell differentiation.

Adaptional evolution of trichome in Caragana korshinskii to natural drought stress on the Loess Plateau, China

“…Because GIS2 is a homologue of GIS , they can be encoded with the same functional protein (Gan et al. 2007). The downstream gene of GIS , the TTG1‐bHLH‐MYB regulatory complex, must be further examined to determine whether it acts in the GIS2 downstream.…”

“…MYB‐bHLH‐WD40 complex combines the promoter GLABRA2 to activate the trichome reaction, and several C2H2 transcription factors act upstream of GL1 to regulate trichome initiation (Gan et al. 2007; Zhou et al. 2013).…”

Rice Cytokinin GATA Transcription Factor1 Regulates Chloroplast Development and Plant Architecture

“…GA controls many important aspects of development, including seed germination, stem elongation, and flowering (GreenboimWainberg et al, 2005). Evidence indicates that there is significant cross talk between GA signaling and another class of phytohormone, cytokinins (Gan et al, 2007;Weiss and Ori, 2007;Steiner et al, 2012). Cytokinins are key regulators of plant growth and development, including cell division, chloroplast biogenesis, differentiation, stress tolerance, and organ senescence (Argueso et al, 2010).…”

GeBP and GeBP-Like Proteins Are Noncanonical Leucine-Zipper Transcription Factors That Regulate Cytokinin Response in Arabidopsis

“…GeBP is predicted to play a role in hormonal pathways on the basis of the following observations: (1) the GeBP protein binds the cisregulatory element of the GLABROUS1 gene, a myb-gene regulated by GA and cytokinin hormones (Perazza et al, 1998;Gan et al, 2007) involved in epidermis cell determination (Oppenheimer et al, 1991); and (2) transcript levels of GeBP are positively regulated by BRE-VIPEDICELLUS (BP; Curaba et al, 2004), a gene of the KNOTTED1 homeodomain (KNOX) family that positively regulates the cytokinin pathway in the shoot apical meristem (SAM; Jasinski et al, 2005;Yanai et al, 2005). Hormones such as cytokinins, GAs, and auxin are involved in the establishment of the balance between the production of organs from the flanks of the SAM and indeterminate growth at its center.…”